STABILITY OF DISPLACEMENT VESSELS
Concordia’s voyage from glory to a point of no return
CASE STUDY OF COSTA CONCORDIA
Ships’ self-empowering mechanism to battle the deadly waves
REVEALED of Reality
“Everything is connected”
Mr Raunek Kantharia FOUNDER & chief editor, MARINE INSIGHT
NAVISIEGER L E A R N
S H I P
D E S I G N
I S S U E
2 0 1 9
avisieger” can be directly translated as “Conqueror of the oceans”. Mankind has witnessed extraordinary development only after the onset of transportation and trade. Water transport undoubtedly has a paramount contribution in the blooming world trade facilitating 90 % of it. Humans
could exploit water transport only due to the great invention and humongous evolution of ships. These vessels have come a long way from being simple boats made up of wooden logs to enormous ships, heavily loaded with powerful machinery and the trickiest technologies.
Today they can overcome all sorts of uncertainties in the oceans. With the cumulative efforts of naval architects and ship builders across the globe, multifarious conditions and risks have been analyzed. Technologies have
been incorporated and designs have been modified to accommodate almost all possible loopholes. Hence it is evident that a modern ship can literally “conquer the oceans”.
With Navisieger we bring to you the insights of these Naval Marvels
E H T M O R F
D N U O F What started as an idea to learn & spread the vast knowledge of Naval Architecture, and to cultivate the interest of students/ enthusiasts from all spheres in this dynamic yet highly regulated field of study, to the level where it is now, I am so proud & confident that its reins are in the right hands. I am sure; the team will continue to excel and push their limits to bring in the latest in the field to our readers. Once again, congratulations to the team on their first edition of â&#x20AC;&#x2DC;Navisiegerâ&#x20AC;&#x2122; and happy reading to our regular followers.
S R E D Over the years, Learn Ship Design has evolved from being a student society of naval architects, to one that aims at enhancing industry-academia confluence in the maritime technology sector. This sense of shared ownership and contribution has enabled the team to constantly evolve and redefine its limits. The Navisieger Magazine is a small but significant step towards our goal. The fact that our partners have seen value is this initiative, is encouraging, and a responsibility at the same time. My best wishes to the team. I hope this issue adds value to our stakeholders across industry and academia.
LSD TEAM OF 2018-19 (ROW -1)L-R: ZIA UR RAHMAN, INDRANIL KUNDU, SOUMYA SAMEER, SURYADiP GHOSH, RAJIV RATNa JHA, ANAGHA S., VIBHA DINESH SHARMA, TAMOGHNO BANERJEE, SRIHARI SIVASUBRAMONY, SAMBORTa Gongopadhyay(ROW - 2)L-R: SUNAND KRISHNA, KARTIK GARG, SHIVANSH SINGH, RIJAY MAJEE, ANIL SINGH, KUSHAGRA GUPTA
Navisieger editor in chief shivansh singh SENIOR editor RIJAY MAJEE SENIOR TECHNICAL authors ANIL SINGH, KARTIK GARG TECHNICAL authors ZIA UR RAHMAN, SOUMYA SAmeer, rajiv ratan jha, suryadip ghosh jr. technical authors anagha S. srihari SIVASUBRAMONY, vibha dinesh sharma, tamoghno banerjee
LEARN SHIP DESIGN
CHIEF OF DESIGNING INDRANIL KUNDU WEB DEVELOPMENT HEAD KUSHAGRA GUPTA Jr. web developer samborta gongopadhyay Photography head sunand krishna
hips have been, by far, the most efficient and economically feasible machines facilitating global trade. Education and research in ship design and shipbuilding are practiced by universities all over the globe. In spite of the availability of engineering and management talent, cheap and skilled labour, and geographical advantages, Indiaâ&#x20AC;&#x2122;s contribution to the global shipbuilding industry has been limited compared to the leading economies in this field. In light of this, two aspiring naval architects from Indian Maritime University, Visakhapatnam Campus realised the importance of a platform that would facilitate a confluence of the industry and the academia. Learn Ship Design (LSD) is Indiaâ&#x20AC;&#x2122;s first student-managed society that strives to achieve this goal. The idea was to create a forum that brings industry insights into academia, thus enabling aspiring naval architects and marine engineers to develop themselves into industry-relevant professionals. This would also enable the academia to constantly evolve its pedagogy and leverage the findings of research and development efforts to create application-oriented course offerings. Our next big step towards stronger confluence is to publish the first issue of our magazine with a vision to share real-time insights from industry and academia through a survey report, interviews of industry leaders, and articles from academic experts and students. I would like to present, with great pleasure, LSDâ&#x20AC;&#x2122;s Inaugural Issue of NAVISIEGER magazine. The issue is devoted to the gamut of maritime design and technology, from theoretical aspects to application-oriented studies, and validation of emerging technologies. NAVISIGER is envisioned to represent the growth of maritime technology and shipping industry as an
increasingly vital field in the era of globalisation, now widely recognised as an integral part of the global trading framework. Multiple sources from the academia and the industry have contributed to the creation and development of the magazine. I am thankful to our partners who have believed in us and seen potential in this initiative. This would not have been possible without the efforts
of the young team, and everyone in the community who supported the idea. I hope this issue finds the interest of all stakeholders, and enables them to raise the right questions, discuss the relevant issues, and envision the new frontiers of the rapidly evolving maritime industry.
EDITOR IN CHIEF
f e at u r e d
Chief Editor, Marine Insight
Cdc, Reliance Defence Interview Underwater Image Enhancement
n o i s l u p Pro
Regulars 09-10 IOT on Ships
21-23 Case Study
11-12 Carbon Footprint Reduction
24 notable events
29-30 Doubly Fed Induction Generator
17-18 Intact Stability
33-34 Ballast Water
19-20 Investigating Sunken Marvels
35-36 Damage Stability 39-41 Hull Fairing
Online Find Us On
www.facebook.com/learnshipdesign https://www.instagram.com/learn_ship_design Learn Ship Design www.linkedin.com/company/learn-ship-design
45 43-44 Ship Breaking 45-47 Propulsion 49-50 ship underwater noise signatures 51-52 Safety at Beach 53-54 Naval Architecture terms
ZIA UR RAHMAN
nformation and data have always been counted as valuable entities by humans since antiquity. But the type of data and methods of gathering it underwent a revolution after the invention of information technology during the latter half of the twentieth century. In todayâ&#x20AC;&#x2122;s scenario, a major part of the income for IT giants like Google and Facebook is generated from the ads they run on their electronic media platforms that are targeted based on the data collected from users. Data is collected by many corporations through various
digital impressions of users like search queries, likes, comments, preferences, and purchases. Highly comprehensive analytical tools like artificial intelligence, machine learning, and deep learning are used to boost the significance of such data by generating valuable insights that assist analysts to decide on customer interests and marketing strategies. The fact that data can be collected only through digital impressions generated while using electronic gadgets like cell phones and computers limits many possibilities of extended applications.
Humans interact with various physical entities daily, these interactions, if at all are documented as digital data can help us to reveal marvelous insights about human-object interactions ; thus facilitating research, development, and optimization of current systems resulting in better products and services for mankind. IOT is one of the possible ways to collect data from daily life interactions. Since various electrical and non-electrical objects of regular use are connected to the internet as a result of Internet of Things, they generate huge amounts of valuable data related to daily life activities. A brief description of IoT integration with existing products Primarily the data to be gathered is categorized based on continuity, periodicity, and amplitude of the output signal. The device from which data will be collected is defined. The data formats are settled based on the requirements and abilities of the system in use. The basic need to accomplish this is the need to have a reliable and secure internet connection. Up next, an intermediate connectivity system is required to connect devices to the internet. Usually, this is accomplished by using connectivity modules like ESP8266, HC05 in combination with development boards from Arduino, raspberry pi, and Texas Instruments. These modules help us convert the data into digital formats and send it to the cloud servers via internet. Further up, many systems support bi-directional communication, allowing us to control and manage a number of things wirelessly, making things more interactive and user-friendly. All the data collected from the devices is stored on cloud platforms and can be made available for public use or kept personal. A lot of these clouds services facilitate cross-platform usage and provide computational services but at the cost of the privacy of data at most.
â&#x20AC;&#x153;THE INTERNET OF THINGS IS NOT A CONCEPT; IT IS A NETWORK, THE TRUE TECHNOLOGY-ENABLED NETWORK OF ALL NETWORKS.â&#x20AC;?
Most of the IT companies now host IOT web services, which are mostly free for individual use and paid for corporate use, like Amazon Web Services, Things Speak, and Google Firebase to name a few. These technical leaps will entirely revolutionize the way people interact with their daily life commodities alongside while they gather huge amounts of useful data. This techno-economic real-life data gathering methodology can be very well implemented in the maritime industry. This will gather data generated by the operations of shipping vessels, utility systems, and port operations. Data can then be used to train machine learning models, AIs and will act as a provision for research analytics. Machinery maintenance is an important aspect to be
sure about before vessels sail through the vast blue oceans. IOT can effectively enhance the easy to condition-based maintenance to monitor the state of machines onboard and simultaneously contribute to real-time machine data content, which can help gain insight ful results to improve the design and amend service methodology. Further, these results can assist regulatory authorities in drafting rules and setting standards. These applications promise a great deal of innovation and development in the near future but currently, the cons of this technology hold a seriously precarious reputation due to inappropriate security features.
Security and safety challenges A number of leaked documents and emails on WikiLeaks related to the secretive gatherings in Silicon Valley to discuss various issues regarding security of IoT-smart devices lead us to infer that improper security features of the IoT devices put forward some legitimate concerns that need to be met with before implementing them on relatively larger scales. One of the newly emerged problems is that hackers can use the hacked IoT devices to send automated emails without the consent of the owner. This loophole can be exploited to imitate the situation of distributed denial of services and cause
All we need is to develop technology in a sustainable manner
harm to large corporations by bringing down their stock rates and profits. There have been reports of government agencies and other corporations spying on commoners by hacking their cell phones and computers. Considering the vulnerability of IoT devices, one can easily predict the massive advantage these entities will have, to exploit the privacy of large masses without any noticeable offense. IoT is a multimillion dollar industry which has sought interests from big players of IT-industry like Google and Amazon. Thus it will definitely grow into a much larger business by the end of this decade, possessing a potential to impact humanity in an unpredictably substantial manner. All we need is to develop technology in a sus-
arbon Foot Print (CFP) is the total set of GHG (Green House Gas) emissions caused directly and indirectly by an individual, organization, event or product”. The methods to reduce the carbon foot print have been discussed in many forums, technical sessions, seminars and workshops as a process of providing a Carbon sink which is nothing but a reservoir of carbon that accumulates and stores carbon for an indefinite period. The main sinks are the Absorption of carbon dioxide by the oceans Photosynthesis by plants and algae to turn the carbon into plant matter(or)Injection of CO2 emissions deep into geological subsurface. But, in this paper the new technologies of reducing the carbon foot print from the ships while ascertaining fuel savings methods have been discussed. If shipping companies with large fleet are following this method, they can not only reduce the carbon foot print and greenhouse gas emissions, but also save lot of energy in way of reduced fuel consumption which is a greatest benefit to ship owners and operators.
nited Nations Framework Convention on Climate Change (UNCCC) has decided in its KYOTO protocol that the CO2 reduction level (grams of CO2 per tonne mile) for the first phase is set to 10% and will be tightened every five years to keep pace with technological developments of new efficiency and reduction measures. The reduction rate is calculated from a reference line representing the average efficiency for ships built between 2000 and 2010. Reduction rates have been established until the period 2025 to 2030 when a 30% reduction is mandated for applicable ship types. From 1st January 2013 onwards MARPOL 73/78, ANNEX-VI –mandates for all new ships, two important indices, related to air pollution, to be developed and implemented.
Those are Energy Efficiency Design Index (EEDI) & Ship Energy efficiency Management Plan (SEEMP). These values require a minimum Energy Efficiency level per capacity mile (example: tone mile). The level is to be tightened incrementally every five years. Majority of Indian ship owners are not geared yet to implement this mandate into their fleet. From 1st January 2013, all ships over 400 GT on international voyages will be required to carry a Ship Energy Efficiency Management Plan (SEEMP), detailing the operational and technical measures that will be implemented on board to improve efficiency and therefore reduce fuel .Appendages to the propulsion system at the stern of a vessel can offer ship owners and operators an easy and relatively painless solution to improving fuel efficiency without the need to order
new and expensive ‘eco-ships’. SOME CONTEMPORARY TRENDS: While discussing about some contemporary trends in the world for achieving the Marpol Annex-VI mandated results, several technical developments have taken place both nationally and internationally. Herewith, few such technological developments are discussed. A Japanese shipbuilder - Imabari Shipbuilding has introduced a unique solution that could help combat two of shipping and maritime biggest challenges; (i) piracy and (ii) energy efficiency. They developed a technology, called Aero-Citadel, by introducing a streamlined and aerodynamic shape to a ship’s superstructure and other advances in the vessel’s accommodation block, engine room, and funnel casing.
GREENHOUSE GASES from ships
The design also includes a built in citadel along other piracy prevention measures. The exterior design was developed through extensive wind tunnel testing that Imabari says could potentially lead to a reduction in wind pressure and drag by up to 25 or 30%. In the Aero-Citadel technique used for the design of a vessel which has been used by Japanese Shipbuilder â&#x20AC;&#x201C; Imabari Ship building, all stairs leading to the bridge are placed on the inside of the superstructure and the entrance on lower level deck is equipped with thicker, reinforced steel doors to make it more difficult for intruders to enter.
doors. Inside the citadel, the facility features communication equipment running on its own independent power source, ship maneuvering equipment that can shut off the main engine and steering gear, and surveillance equipment allowing access to vessel data, including video, picture and sound. In addition to the unique superstructure shape and anti-piracy measures, the accommodation block features energy efficient LED lighting and noise and vibration insulation for enhanced crew comfort, and a wheelhouse with a widened backward view for safer navigation.
In addition to the stairs and entranceway, the windows are equipped with bulletproof glass, and water cannons are placed on the upper deck to help blast attacking pirates. The superstructure also includes a citadel with enough supplies to accommodate crewmembers for several days, and is protected by double-layer security
The above described vessel is one of the contemporary design methods which will meet the EEDI, SEEMP & EEOI requirements, because the Ship Energy Efficiency Management Plan (SEEMP) is ultimately an operational measure that establishes a mechanism to improve the energy efficiency of a ship in a cost-effective manner. The SEEMP also
provides an approach for shipping companies to manage ship and fleet efficiency performance over time using, for example, the Energy Efficiency Operational Indicator (EEOI) as a monitoring tool. The guidance on the development of the SEEMP for new and existing ships are given in (MEPC.1/Circ.684). The SEEMP urges the ship owner and operator at each stage of the plan to consider new technologies and practices when seeking to optimize the performance of a ship. The EEOI enables operators to measure the fuel efficiency of a ship in operation and to gauge the effect of any changes in operation. For Example (i) for improved voyage planning, (ii) to adopt more frequent propeller cleaning, and (or) (iii) for introduction of technical measures such as waste heat recovery systems (or) use of a new propeller etc.
Needless to say that all of us being a part of the maritime industry are ubiquitously biased toward the principal aspects of ship design and construction such as stability, resistance, propulsion, marine construction, material science, hull form design and other multifarious aspects. But another aspect which is ineluctably lurking in all these is Hull Outfitting. Though simple and seemingly redundant, it is a part and parcel of shipbuilding. Better to say, it is perhaps the most ‘value-based’ phase of the construction cycle of a ship. Outfitting comes under the head of Contract Design and is carried over to the phase of Technical Design till the commissioning/ delivery of the vessel. That is, when the vessel has been negotiated between the builder and owner part after meeting all the requirements of design, performance, capabilities and
WHAT IS OUTFITTING?
utfitting or Fitting-Out is the process in shipbuilding that succeeds the phase of launching and continues till the final delivery of the ship. When the vessel is launched, it is complete from structural and functional point of view. However, there is a requirement of an integration of various systems and subsystems of a vessel to make it fit to be operational. Though there is no proper demarcation of outfitting, following activities are pertaining to outfitting: • Finishing job of the superstructure and bridge • Installation of ship’s power plant, machinery and related systems • Electrical Integration, wiring, cabling and systemization • Plumbing • Carpentry • Installation of various equipment and subsystems
• Installation of several deck mounted items (bollards, capstans, cleats, towing and mooring arrangements, guard rails, lifting and cargo stowage equipment and so one) • Piping works • Installation of various armoury (for defence vessels) • Fire-fighting equipment • Day-to-day household items requisite for accommodation
spaces • Insulation • Painting This list is seemingly endless. The main crux of hull-outfit is the
final stage completion before handing over of vessel to owner party. Outfitting encompasses a plethora of hot work and cold work. Hot work includes welding of various items, heating, moulding, drilling (for cables, wires, pipes) etc. whereas cold work involves bolting, riveting of equipment, marshalling, relocation of items from one place to another. Obviously the hotwork precedes the cold work. Let’s have a quick example in this regard. Suppose there is a need for installation of an electrical transformer at a particular location on a vessel. Firstly, the hotwork IN THE PAST needs to be < Fitting-Out of Russian Battleship completed Poltava in terms of drilling routes for wires and cables, fitting of cable tray, welding of frame to set up the item. Then the cold work is performed in terms of marshalling
WORKFLOW OF HULL The process of outfitting or fitting-out is a systematic job involving coordination of different heads in tandem. Although seemingly simple, it involves huge analysis and feasibility studies with main contribution from the design team which is materialized by the shipyard. 1. Firstly the structural drawings of the vessel are completed. Structural or basic/detailed drawings are precise drawings encompassing structural members like plating, angles, brackets, stiffening members, stringers, beams etc. arranged as per classification guidelines and under the sway of design office of the
model of the entire vessel is generated. Real-time simulation of various components helps in precise analysis of the entire vessel. In most shipyards, the system of discretization into zones is followed. This involves division of the vessel into several entities where each is separately assessed. The entities include structural items, outfitting items, piping, electrical and so on.
3. Then as per the ‘Build Specification’ and ^HOW IT LOOKS Structural drawing cum arrangement layout of owner’s requirement a all the fitting-out tasks are accomplished. As concerned organization. mentioned earlier, the hotwork precedes the cold work mostly. 2. In modern day shipyard practise, this is succeeded by mod4. The ‘Fitting-Out’ task is mainly elling with the help of software done after the launching of the tools where a comprehensive 3D
vessel. However, some outfitting jobs like installation of heavy machinery are done prior to launching for weight purposes. The process of hull-outfitting involves three principal parties: • Shipyard or shipbuilder • Owner Party • Vendors All three segments play quintessential roles in dealing with the process. The owner specifies the necessities. The shipyard and the designers chalk out the schedule and the plan for the installation of various items in desired locations. Now, the yard procures most of the materials from the vendors. They may be fabricated in-situ shipyard or outsourced. For example, most of the big shipyards fabricate items like deck fittings, piping, anchorage or various steel fitting. Also a lion’s share of items may be procured from outside like cranage, eclectic range of machinery and electrical components, insulation, equipment, furniture, modular compartments and so on. A continuous dialogue between the yard and the vendor or the yard and the owner takes place. The yard/design office has a significant amount of freedom to arrange and rearrange the items based on convenience, space availability, and work schedule status, criticality of job and most importantly, availability of the outfit item during the desired time.
In most of today’s ships, accommodation spaces are being made modular. Modular spaces
FACTORS GUIDING THE PHILOSOPHY OF OUTFITTING
^HOW IT LOOKS Crane placed in line with transverse bulkhead
Ostensibly, outfitting is a simple task. However, it involves several intricacies of basic design. Though one in-charge of suiting “at-site” in shipyards are more informed of the various situations, the design office plays a catalytic role in corresponding with the yard in various kinds of practical problems. Some, out of a multitude are: • Arrangement: It is crucial to place the items without compromising accessibility and most importantly, utility. Space is the most important
consideration. The design department spends considerable amount of time to assess the space utilization for all outfit items. This is aided by modelling tools showing with high accuracy the real-time visualization of various spaces. Just like time, space in ship means money. Obviously in commercial vessels, also in defence or other purpose vessels, all designers aim at optimising space to the highest extent without compromising unhindered functionality.
• Strength and continuity: Placement of any item requires proper assessment of load path for strength. For example, a crane is placed on the deck ideally in line with a transverse bulkhead for continuity of strength. • Interference: Proper care should be taken such that the arrangement of items does not cause unnecessary interference. A proper planning is slated out by the design department with an approved layout of items such that neither there is fouling nor disuse of accessibility. <HOW IT LOOKS Sample Ladder plan of undisclosed vessel
• Networking: For pipelines and cables, a defined network is carved out keeping in mind basic aspects like (i) Minimum Length (ii) Least interference (iii) Lesser proximity to danger zones and if they need to be vicinal to them, (iv) proper protection.
^HOW IT LOOKS Sample arrangement of bulkheads in undisclosed ship
â&#x20AC;˘ Risk Factor: As setup of outfit items require several types of hotwork, care is taken for guidance based procedures to avoid flammability, short circuits and destruction of material or items caused by hotwork. A work schedule is always given by the concerned design department such that the critical tasks are accomplished safely beforehand and without compromising the minimum risks. Critical jobs near prone areas like major electrical or machinery installations are done with utmost care. â&#x20AC;˘ Weight considerations: Like strength, weight considerations are also taken into account. Installation of heavy items are carried
out with utmost care with adherence to strength, continuity and location. Although, outfitting is majorly an after-launch process, several heavier items are placed beforehand. All items are placed keeping in mind the load distribution and critical areas where there can be a chance of imbalance. For example, if there is a requirement of installation of some heavy deck equipment onboard, first a reconnaissance of the structural details at that particular location is assessed. Since a heavier item requires more load bearing capacity, the plating in that
area may be stiffened further. Also, the item may be placed in line with heavier scantling structural members as mentioned earlier. Or if a heavy machinery is to be placed in some low tier deck. The machinery may be placed on a foundation structure
affixed to that deck, which in turn may have higher scantlings or additional stiffening. Furthermore, during stowage of these equipments, care should be taken to avoid damage of both the structure and the items themselves.
^HOW IT LOOKS Mooring and berthing arrgt. of undisclosed ship
With all stability data available and with designs close to perfection, it has been made possible by man to cruise through the biggest of oceans and still be untouched by the salty waters.
INTACT STABILITY rajiv ratna jha
n the deep devastating seas where a mere human has no significance, ships’creation braves through the waters. Ships are one of the biggest accomplishments mankind has ever achieved. Safety is one of the key aspects of these marvellous creations, which is greatly achieved through its stability. Stability, in simple words, is the ability of a ship to sail in waters without capsizing or being overturned; being neither too tender, nor too stiff despite the various internal and external heeling, listing, trimming, turning and bilging factors. A ship is stable when the net force and the net moments of these forces exactly cancel out according to the laws of vectors analysis. The weight of the vessel is balanced by the fathoms-deep oceans itself. These two forces are aligned exactly opposite to each other, nullifying each other’s moments. The concern of stability arises when the unbalanced external forces are exerted or when the weights within the ship are moved in an unplanned fashion. The moments created are huge and tend to capsize the ship. A displacement vessel floats in water in accordance with the Archimedes’ principle which states that, if any object is immersed in a liquid, it expe-
riences an upward thrust, called the buoyant force which is equal to the weight of the fluid displaced by the immersed body. This force acts on the centroid of the immersed body. For a ship, the centroid of its immersed portion is its center of buoyancy. As the ship heels, lists or trims, a capsizing moment is created due to the factors like free surface effect, shifting of weights onboard, effects of winds, effects of icing, loading of cargo or bilging. As a result the underwater centroid shifts from its original position to counter the effects. This is where good design is required to effectively counter these moments of upsetting forces. Stability calculations of a ship require the identification of four important points: keel of the ship (K), center of buoyancy of the ship (B), centroid of the ship (G), and metacenter of the ship (M). The distance GM is termed as the metacentric height. A positive metacentric height is required to produce a torque by the virtue of buoyant force which can counter the upsetting net torque. For an initial negative metacentric height, the ship would initially get stable at the angle of loll.
GZ CURVES For an unstable ship
If a ship returns to its original position after the external force is removed, the ship is well designed and is said to possess a stable equilibrium. Huge righting moments arise due to the upsetting moments and keep the ship from capsizing. The measure of the stability of a ship can be estimated fairly by the length of its righting lever, conventionally denoted by GZ. When a ship is wall-sided, i.e., no part of the deck is immersed in water and no part of the bilge is out of the water, the righting moment arm length for a ship for angles (x) roughly up to 250 is given by the WALL- SIDED formula: GZ= sin x [GM + 0.5 BM tan2 x] GZ cross curves are used to determine the righting lever arm length to determine the GZ values at different displacements of the vessel for different angles. The same measure GZ also provides us the ability of a ship to capsize by its weight by the slightest of heel or list if the location of metacenter is below the centroid of the ship. Plotting the GZ curve requires the knowledge of the location of GM. As the vessels’ loading conditions differ from a voyage to voyage, another curve that is the righting lever arm length measured from the keel of the vessel is plotted. As the keel is uniquely identified for a ship and is a property of ship and independent of the loading conditions, KN cross curves are legit for all voyages. GZ and KN curves are related as: GZ = KN – KG sin x Once the loading of a ship is done
and the centroid is ascertained for a voyage, GZ curves can be plotted using the KN curves. The steeper the GZ curves are, the more is the initial stability of the ship. As the catamarans are more stable, its graph is way steeper than a typical monohull. The statical stability curves are obtained by plotting the GZ values against the angles of the list. This curve dictates how stable a ship is for all angles. It provides an insight about the angle of initial stability, the angle of loll, the range of stability for all angles of heel, the maximum GZ value available to a ship, the point of contraflexure, initial metacentric height and the point of vanishing stability. The area under the stability curve times the displacement of the vessel tells us the energy required to heel the ship to that angle. The most important tool to measure a ship’s stability is its hydrostatic curves. Different properties of a ship plotted on a graph of the draft against displacement gives all the important data like TPC, MCT 1 cm, LCF, LCB, etc. This data become essential when listing occurs due to factors like free surface effect. Designers discovered the free surface effect by example of MS Estonia ( IMO Number: 7921033) and took measures to reduce it. In the free surface effect, the center of gravity of partly filled tanks shifts resulting in the shift of the entire center of gravity of the ship. It may seem insignificant at first, but for a ship carrying lakhs of tonnes of any liquid by weight, it is enough for it to earn its name in the list of sunken ships. This listing effect has to be approached intelligently by creating more compartments for storage of liquid and by keeping the tanks as close to full or empty. To monitor effects like this
and other factors that could alter a ship’s stability, INTERNATIONAL MARITIME ORGANISATION has laid down certain criteria for ships to follow. It has set regulations on: • The area under the stability curve should have at least a minimum value, for each specified angle, as specified by the IMO for that ship type. • Initial metacentric height. • Weather criterion for safety against heavy winds. • Availability of a stability booklet on the ship. Many other general regulations and
STABLE EQUILIBRIUM Of a ship in the stable conditions
many regulations depending on specified ship types have also been laid to ensure safety at sea. Inclining experiment is also recommended as the first test of stability. In the inclining experiment, the metacentric height is calculated first. This can give an idea if the built ship has a neutral, stable or unstable equilibrium. When the ship would heel in the inclining experiment, it will return to its original position when the weight is replaced to its original position when the ship would possess stable equilibrium. For an unstable scenario, the initial effect will be a capsizing, until the ship attains an angle of loll where it is in neutral equilibrium. A designer must aim to attain a stable equilibrium for a ship to keep all its voyages safe.
VIBHA DINESH SHARMA
he vast blues provide extravagant money-making opportunities by being a major stakeholder of the transportation business. World trade highly depends on water for transportation of various commodities. With the increasing demand, human voyages to the oceans have sky-rocketed. Ships being the protagonists of the show are exploiting the blue resource to a great extent. Theyâ&#x20AC;&#x2122;re massive monetary investments which generate equally bulky revenues. But there are a thousand things that can possibly go wrong in the ocean. Despite the beauty of maritime advancements, marine accidents are heavily destructive. The consequences of such incidents include large scale damage of the vessel, loss of cargo, casualties and harmful environmental effects. Shipping accident also proves to be a tremendous financial loss. History has witnessed the best of ships surrendering to the ocean. Sinking of German Wilhelm Gustloff in January 1945 in World War II when it was hit by three torpedoes engulfed 9400 people and is till date the largest loss of life occurred. The Philippine-registered DoĂąa Paz sank after colliding with the MT Vec-
THE SUNKEN MARVELS
tor on December 20, 1987. Due to the gasoline barrels which it was carrying, the ship and the surrounding water was set on fire. Well, the most dramatic one still remains RMS Titanic which sank on April 15, 1912, after colliding with an iceberg during her maiden voyage. So all major accidents are thoroughly scrutinized and investigated, to prevent similar mishaps in the future. Here is a brief description about the protocol which the investigating bodies follow.
The primary purpose of an investigation is to look for causes that led to the accident to determine liabilities of affected parties and to find corrective measures. The process begins with promptly notifying key personnel about the incident. Then the emergency Response Activities begin. The primary goal of the emergency response troop is to prevent further injuries, property damage, and environmental impact.
After this phase specifically authorized personnel of the investigation team is allowed access to the incident site. Once access to the site is granted, the predefined “Initial Incident Scene Tour Checklist” of various investigation bureaus assists the personnel to capture required data. The investigating team then carefully scrutinizes the site and collects data which includes- equipment, on-duty personnel details, photos, papers, position information, and retrievable electronic data. In many cases, the emergency response team during its course of action alters the original data making it difficult to recreate the original scene. The incident aftermath is precisely defined. What equipment, structures, items, cargo, and systems were involved, who was involved, when did it occur and every other minute detail is recorded. Multiple loss events are identified to address different types of losses and the respective stakeholders associated with it. According to the protocol of many organizations, generating a Corrective Action Request (CAR) is the first step towards the incident-specific investigation. CARs are often the first form completed when any problem arises.
identify root causes that are controllable, for exampleweather cannot be controlled, though, how preparation occurs for operation in different climates can be. Root causes are deep enough that identification of deeper underlying causes could be unproductive, so only those which can be reasonably addressed with recommendations are identified. From the gathered data, a sequence of events and circumstances under which that may have occurred is developed. Then the unsafe acts, decisions or conditions are identified by tabulating many factors like- problem and its category, cause category and type, intermediate cause, etc. and finally a conclusion is reached. Finally, there is very rarely one cause for an incident. Multiple safeguards exist to prevent any incident worth investigation; numerous failures of those safeguards have to occur to generate an incident. This is in accordance with the famous “Swiss cheese” model of accident causation, which is applicable across many safety-critical industries. In this, the safety of a system is considered as a series of barriers or “defenses of depth” against the potential of failure. The presence of one or
Mistakes are meant for learning lessons and aren’t meant to be repeated. Investigations have proven to be the stepping stones for enhancements and refinement of maritime sector and will further continue its assistance. They are also generated for preventative actions (e.g., near-misses, opportunity for improvement or to alleviate conflicts within the management system). If a deeper analysis on the sequence of events, the interactions between personnel, the interactions of the management systems and the underlying causes of the incident are required to formulate effective corrective actions (recommendations), then the case undergoes an Apparent Cause Analysis or Root Cause Analysis. The incident reported by the CAR is then assessed against the incident classification criteria. Incidents are then classified according to various parameters like their type- Accidents (collision, spill, grounding, explosion, fire or sinking), Near misses (near collision or failure of critical safeguard) or other incidents like machinery upsets or quality variation. Then comes the primary step of the investigation- the “root cause analysis”. For almost every incident ,some refinement in the management system has the ability to avert most contributing factors. We can basically conclude that the absence, neglect of deficiencies in system features are the fundamental root causes. We
more barriers will prevent the accident, sometimes only the final barrier will hold (a near-miss), but very occasionally all the loopholes will align, the safety barriers will get penetrated and accident will occur. The most important products of investigation are the recommendations devised from it. Only those recommendations are accepted which are actually implemented or later proven to be effective. They should be practical, feasible, and achievable and should be assigned to someone along with completion date whether it’s short or long term. Recommendations need to be reviewed as a part of the management of change process to ensure that they solve more problems. The main motive is to look for massive benefits with minimum harm and expenditure associated with them. Then a detailed investigation report is prepared and is communicated to the concerned authorities. In this way the investigation process is concluded. After investigations many ships make it to the shipwrecks while a few antics make it to the museums, and become a source of amusement for generations.
[CASE STUDY I
t is said that history often repeats itself . After 100 years from 1912 when the Titanic met its unfortunate fate , a similar incident happened with a famous cruise ship making it second in the line of the most infamous shipwrecks.
The ship Costa Concordia was operated by the notable Italian cruise line Costa Conciere which was established in 1854.Since the year 1947 when the company commenced passenger services it has established a good reputation over the years and ultimately became one of the largest cruise operators in the world. However the capsizing of one of its star cruise ships barely 7 years in service not only left a dent on the companyâ&#x20AC;&#x2122;s reputation but also raised serious concerns over international cruising. The following article sheds light on the reasons behind the capsizing as well as lists out the circumstances that led to the disaster.
SHATTERERD UNDER ITS OWN HEAVINESS The starboard side of the ship was completely crushed under its own weight.
On the night of January 13 , 2012 Costa Concordia struck her port side on an underwater reef near the Italian island of Isola del Giglio.The ship immediately lost all propulsive power and soon after there was a complete blackout as water reached the electrical panels . The breach resulted in a 60 meter long gash in the ship’s hull.This led to the rapid flooding of the watertight compartments and ultimately led to its capsize. It’s difficult to comprehend the fact that such an incident can happen given the availability of advanced technology and instrumentation giving precise and detailed information of every possible circumstance a ship may face. From rough seas to mapping of the ocean floor to high speed winds ; all relevant data is available with a ship at regular intervals. The topography of any area in which the ship sails forth is already available on board a ship. A big question arises as to why was the ship sailing so near the coast in the first place which ultimately led to one of the most horrifying disasters in international cruising.
WHAT WENT WRONG?
Most cruise ships perform what is called as a Sail - By Maneuver. The ship takes a slight deviation from its official course to sail near an island just to give the passengers a unique glimpse of it and give a nod to the fellow sailors on land. This is a routine maneuver in cruise lining and has been
practiced successfully across the world for years. The ship’s deviation course is plotted in such a way so that it is at a minimum safe distance
By the time the captain realised the situation and started giving a series of orders for rudder turns it was too late as the ship was already in too close proximity and moving at a speed of 16 knots.
PLANNED ROUTE WITH DEVIATION. Red Line shows the route followed by Concordia on the day of disaster
from the island to prevent any situation of grounding in shallow waters or due to the presence of rocks and reefs near the coast. Concordia had earlier also performed it for the same island in its past voyages . So what possibly went wrong this time endangering the lives of around 4000 people on board which would ultimately change the cruising industry forever. Concordia’s deviation course required it to stay at least 1500 ft away from the island. But as it turned out the ship landed up around 659 meters closer to the coast. This egregious error due to a series of miscommunications between the captain, first officers and the officer at helm was reflected later in the investigative report. Because of the incorrect heading angles , the turning radius of the ship was much wider than it was supposed to be as per the chartered deviation ; ultimately bringing the ship in close proximity to the shore.
The erroneous executions of order by the helmsman and delay in correcting them ultimately left Concordia no chance to pass safely.
Why couldn’t the flagship liner maintain its stability?
So why did such a big and modern cruise liner could not maintain its stability and capsized within an hour of the initial impact. The 60 meter long gash in the ship’s hull allowed seawater to rush inside the watertight compartments at a very fast pace , ultimately flooding 4 of the compartments. Whenever a compartment is flooded the buoyancy provided by that compartment is lost. To maintain its stability the ship ‘sinks’ more on to that side to achieve the required buoyant force to support its weight. As water keeps on flooding the buoyant force is progressively lost and the ship keeps sinking. The change in the transverse center of gravity due to the addition of water lists the ship.
FOR A CHANGE. Comparison with route for the same maneuver performed in 2011
The ship initially listed to the port side and after making a 180 degree turn it listed rapidly to the starboard side finally resting on the shoreline rocks at an 80 degree angle. Whether the ship was deliberately grounded by the captain to avoid complete sinkage in deep waters or it naturally drifted towards the coast due to the underwater currents and winds is still debatable. But the fact that Concordia partially sank resulted in less number of casualties than the case had it sunk completely.
The disaster was declared a total loss for the ship which costed around 570 million dollars .
sulting in a total loss of around 2 billion for Carnival Cruises.The wreck was finally gutted and sold for scrap.
Century just like it happened in the 20th Century with RMS Titanic.The sinking of Concordia pointed out some pretty gaping holes and incompetency of some of the crew members on board.In its annual report Carnival Cruises reflected the annual losses incurred due to the sinking of Concordia.
PATH. Path showing Collision and Grounding
The salvage operation alone costed a massive 1.2 billion dollars thus re-
Thus human error once again led to a disastrous ramification in the 21st
Better safety procedures and robust techniques must be adopted to regain the trust of people willing to go on board cruises and enjoy cruising in the most spectacular way.
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In an interview with Kushagra Gupta and Subhodeep Ghosh of Learn Ship Design, Subrata shares some insights from his professional experience and perspectives on the landscape of the Indian shipbuilding industry.
Subrata Mitra is the Chief Design Consultant at Reliance Naval and Engineering Limited (RNAVAL). He engages in professional consultations for various types of ship design activities and special purpose ships. A veteran of the Indian shipbuilding industry, he has over four decades of experience in defence shipbuilding at Garden Reach Shipbuilders and Engineers Limited. As the Chief General Manager, Design (GRSE) he spearheaded the design of six Hydro-graphic survey vessels, five P-25 and P-25A Corvettes, three P-16A Frigates, five Landing Ship Tanks, P-28 Kamorta-class ASW Corvettes for the Indian Navy, and SDBs, FPVs, and IPVs for the Indian Coast Guard. He also led the Planning, Production, and Yard Modernisation functions at GRSE.
From an Assistant Manager to the Chief General Manager at GRSE, please brief our readers about your journey and also throw some light on the work culture and ethics at GRSE and how it has sustained in the Indian shipbuilding industry for decades now. The journey of almost 4 decades has been a momentous one. GRSE, one of the catalytic players in the Indian shipbuilding scenario, has grown from strength to strength needless to say in terms of the technological capabilities, projects, shipbuilding-friendliness and most importantly, readiness. I emphasize on the last one as there is a misnomer that public sector shipyards slog on projects. But it’s not so. As there is seldom a paucity of funds, manpower, technical backup and also, good planning, we were ready to build the vessel within a given timeframe. As of work culture and ethics, GRSE is a place where a lion’s share of most projects has been done to the cent per cent satisfaction of the defence clients. This has welcomed more projects in tune with India’s growing defence strategy. I believe this is an answer to your question.
How do you think an Electrical Engineering background has enabled you to achieve a leadership position in the Industry? Also, which skills did you acquire during that phase of transition that helped you in the long run?
I think this is a very simple question. Name me an industry where there is no requirement of electricity (laughs). Electrical Engineering is a part and parcel of the shipbuilding industry, needless to say. And it’s not a transition. I am still very much associated with the electrical department of ship design. But yes, electrical engineering in ship design and construction is a very intricate process. And as for naval ships with high-end capabilities, I believe it’s more. I have no definite answer to this. Maybe, the experience gathered over the years, the quest to handle all critical problems and proper team management played a role.
There must have been numerous management challenges that you faced throughout your career. Could you please describe any one of your favourites and how did you overcome it? Look, shipbuilding efficiency is honed by practice, unlike any other field of engineering. Shipbuilding is better accomplished by actually doing shipbuilding. So the challenges were many. No specific one, but in almost every project. I have no favourite as such. But they were more or less on the same lines. Naval vessels are high precision jobs. And defence bodies are never happy with a design in the first go. Especially, in the detailed design stage, many alterations had to be made within a limited frame of time. It was design, redesign and so on. Balancing conflicting aspects like outfitting, machinery and piping works simultaneously in advanced stages of shipbuilding was an obvious challenge. In April of 2016, The Government of India launched a Shipbuilding Subsidy Scheme, providing financial aid amounting to 20% of ‘Contract Price’ to Indian Shipyards for Shipbuilding projects signed between 2016 and 2026. Do you think this step has succeeded in attracting commercial shipbuilding projects to Indian yards?
Recently, the Project-75 India, to build six new generation stealth submarines, was included in the ‘Strategic Partnership Model’ under which Indian Shipyards will collaborate with foreign shipyards, under the ‘Make in India’ policy of the Government of India. What are your views on this? I personally believe that was destined to be the one and only option. To build indigenous submarines, Indian shipyards need this kind of an arrangement where there will be a balance between 'Make in India' as well as foreign investment, technicalities. This has a long way to go. Can a similar model be incorporated to attract commercial shipbuilding for the Indian yards? That depends on the project type, the cost involved, and the 'readiness' of the yard. How do you think collaborating with other countries for commercial shipbuilding will benefit Indian yards? Definitely. This will lead to a promising welcome for more projects. More projects mean more income, without compromising overheads. A much-needed option for the upsurge of the shipbuilding industry in this country.
Q+A Honestly, I have no strong answer to this. Two reasons- I retired from active governance of a government-aided enterprise long before this. Secondly, this has more adherence to commercial shipbuilding as opposed to naval shipbuilding, which I have spent the most time on. I can say that as it is still in its baby steps, there is a long way to go. But there is a strong requirement for its success. The shipyard must have a proper implementation strategy for financial aid without squandering it on redundant and stagnant aspects.
In what other ways can the Indian shipyards attract commercial shipbuilding projects?
Well, better technology, infrastructure and skill exploitation in the first place. Both go hand in hand. Another is investment-friendliness, much like other industries.
You have been the CGM for yard modernization at GRSE. In which areas of Shipbuilding technology do you think there is potential for advancement in Indian Shipyards?
Design, planning, production facility, standardization, established vendor base, and process improvement. These are the crucial areas. There always an insatiable room for improvement.
Which managerial skill do you think played a key role while you were heading the production of INS Sutlej?
I was the father and mother of the project! I was the Head of Production. My role was to convert the drawings and blueprints into the ship and corroborate to the materials. I used to dovetail the planning in such a manner that the critical path for the project timeline can be compressed, reducing the delivery time. That project was close to my heart, indeed.
How have the industry expectations from naval architects evolved over the last two decades? In earlier times, the shipbuilding industry was more dependent on other engineering disciplines. Now with informed naval architects, synchronization of the design with production is easier and more efficient. What skills do you think would enable naval architects to eventually take up leadership positions in the industry? I would say more proactive involvement in all aspects of the project rather than restricting themselves only to the concept and basic design stage. They should have more participation in the production stage, I feel.
What are the major differences that you see between the shipbuilding industry in India and in other countries with respect to R&D and government support? This too is variable. It depends on the scenario. In India, it is getting better with more government support and R&D. One noticeable aspect is the exorbitant tax regime still persistent in the shipping as well as shipbuilding sector that still plays leverage in the cost cycle. This needs to be worked upon more strategically. Where do you see the Indian Shipbuilding industry ten years from now? The defence sector has, undoubtedly, a bright future. As of commercial, more time, money and dedication needs to be put in the R&D like most shipbuilding heavy nations. From a monetary point of view, a win-win scenario needs to be harnessed from the shipyard to attract big investments. This is related to better management of resources and use of manpower in a time-efficient way to fast yet proper accomplishment of projects.
Sir, do you have any special message for our readers? Do well. And most importantly, learn, because efficiency comes with knowledge. Experience comes with time. Then these two make you a successful person who can lead yet who never ceases to learn. It's a continuous cycle.
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DOUBLY FED INDUCTION GENERATOR IN SHIPS US RAMESH â&#x2C6;&#x2122; FARZAN HYDER
hat is DFIG?
A Doubly Fed Induction generator is a 3 phase induction generator where both the rotor and stator windings are fed with 3 phase AC signal. It comprises of multi-phase windings located on both the rotor, stator bodies and includes a multi-phase slip ring assembly to transmit power to the rotor. It is used for generating electricity in generators.
Where is it being used?
Wind turbines- In variable speed wind turbines, the rotational speed of the wind turbine rotor is permitted to change as the wind speed fluctuates. Usage of asynchronous generators is prevented in this case to avoid grid failure, as the frequency and voltage output vary. The same is true for synchronous generators which operate at a constant speed when connected to the grid directly. DFIGs are different, they enable the generator output voltage and frequency to be maintained at constant values, irrespective of the generator rotor speed and wind speed.
This mechanism can be used in ships especially where the power variations are common. A Tug is an example of such a ship where the load profiles vary according to loitering, transit and assist mode. Examining the load profile of the tug, it is evident that the power requirement whilst operating is complex. Tug is operated at its maximum load for 2 % of the operating time. Transit and Loitering mode account for low power demand i.e. 15% and 10% of the maximum operating load respectively. This illustrates that tugs are operated at low loads for a considerably long time. This operational attribute drops the efficiency of the diesel generator. The conventional propulsion system with a high capacity diesel engine has low fuel efficiency at light loads, whereas the electric tug provides better fuel efficiency by varying the prime movers. So as to keep constant voltage and frequency, diesel engine with constant rpm drives the fixed speed generator, irrespective of operating
conditions and fuel consumption curve of the engine. Hence, by varying the rotational speed at low loads, the energy efficiency of diesel engine shall be accustomed.
Thus, variable speed diesel engine involving synchronous generator is established for a tug to improve the efficiency during part loads. However, it has disadvantages containing: (i) Rating of the Full rated power converter should be equivalent to generator rating. (ii) Increases the cost and size of the system. Hence, doubly fed induction machine (DFIM) is favoured for electric power generation due
to the necessity of partial rated power converters. These qualities of DFIG have augmented the focus towards the advancement of a diesel engine with DFIG for electric tugs. In case of variable speed generator, DFIM is sufficient, as it requires partial rated power converter in its rotor circuit for a varied range of speeds. Currently, there is a study going on in collaboration with Indian Institute of Technology, Roorkee and Indian Maritime University, Visakhapatnam, regarding the effectiveness of DFIG on a tug. Both theoretical and experimental calculations have been carried and the results show a fuel saving with DFIG on board. The paper is to be published soon.
UNDERWATER IMAGE ENHANCEMENT USING DIGITAL IMAGE PROCESSING
he underwater imaging has been trending for a long time now. This is widely used for observing the sea floor. Underwater cameras are generally included in autonomous underwater vehicles (AUVs), unmanned underwater vehicles (UUVs) and in situ ocean sensor networks (SOSN). It is also been done while scuba diving, diving on surface supply, snorkelling or swimming. The primary obstacle faced in during present day underwater imaging techniques are transportation characteristics of light in water and the biological activities at the floor of the sea, the underwater images generally suffer from scattering and large amounts of noise. Hence, there is loss of contrast when the camera is lowered to a significant depth. At deep sea conditions the sunlight with larger wavelengths is usually absorbed by the surrounding water and hence we are unable to obtain detailed images. This loss of colour increases throughout the water column in both horizontal and vertical directions. The secondary obstacle that is observed is the disturbance to internal eco system of the ocean bed. The automated cameras that are fixed with the flashlight act as a huge threat to the underwater life which in turn damages the sea life. This idea proposes a novel algorithm to improvise the state of art techniques and simplify the processes to get clear underwater images by Digital Image Processing using Image Acquisition and Image Processing toolbox in MATLAB. The proposed technique has the ability of extending the range of the underwater imaging without using bulky and costly instruments and that too with a better clarity and henceforth improving the contrast, sharpness and clarification of the image details. This idea is proposed for the present-day scientific research and surveying vessels that are used for reaching the unknown depths of the sea for obtaining information related to the sea life and organisms, provided there is no risk of disturbance to the ecosystem. Underwater environment mainly offers many rare appeals such as marine lives and , amazing landscape, fishes and mysterious shipwrecks. Other than underwater photography, underwater imaging has also been an important point of interest within the different branches of technological and scientific research, such as
inspection of underwater infrastructures, marine species identification and cables , detection of manmade objects , underwater vehicle maneuvering, marine biology research and underwater archaeology. The aim of this paper as explained in the synopsis is to facilitate a process/methodology suitable for underwater imaging. Presently a wide range of cameras are available for the purpose which offers unprecedented versatility for the same. The main aim of the paper is to get better outcome by cutting the cost for the equipment used correspondingly. Image enhancement is referred to as the process of adjusting the digital images so that the results are more suitable for further analysis of the image in the field of science. Example being, removal of the digital noise, sharpening, contrast adjustment and other digital phenomena related to the digital image. Distinguished from most of the digital images, the underwater imaging process has to go through many troubles such as poor visibility under water resulting from the weakening of the propagated light, mainly due to scattering and absorption effects. The absorption process under water gradually reduces the light energy hence it acts as a catalyst for the troubles occurring, while the phenomena of scattering causes differences in the direction of light propagation. This results in foggy and smoky appearances along with poor contrast levels, making far away objects mostly invisible or misty. Usually, in underwater images, the objects seen at more than 10 meters are almost undetectable by the naked eyes, and their colours are faded and foggy because the composing wavelengths are cut according to the water depth in both horizontal and vertical directions. Many attempts have been made to enhance the quality of images and restoring the visibility of degraded images. As the degradation of underwater images is a result of multiple causes, traditional enhancing techniques such as gamma correction or histogram equalization are not a good solution for such tasks. In the previous works that are surveyed, attempts to solve the problem by tailoring acquisition strategies using multiple images, polarization filters and specialized hardware are made. Still the practical applicability of these methods remains a question!
MATLAB AND MARITIME Indranil Kundu Shubhranil Kundu
The proposed method provides a novel and reliable way to enhance underwater images. The method provides segregation of image into Hue, Saturation and Intensity images of the corresponding pixels and then processes them independently. Wavelet transformation provides additional enhancement of the images in order to obtain the best possible approximate image. The state of art models was based on enhancement of the raw image, whereas this method does it by three parallel processes and thus gives better results and improved outcomes. Presently an experimental study is carried out regarding the scopes of improvements in the proposed method in collaboration with Mr. Shubhranil Kundu, Madhav Institute of Technology, Dept. Of Electronics and Mr. Indranil Kundu, Dept. of Naval Architecture, Indian Maritime University, Visakhapatnam. The paper on this abovE proposed topic is to be published soon.
he most common and economic means of transporting goods are indeed the mighty ships sailing all across the vast seas spread across the world. Ships are designed to carry multitude of cargo like oil, grains, machinery, fruits, etc. and of course people. They move from port to port, loading and unloading at every halt. By the Archimedes principle we expect that, with every alteration in the weight of the contents of the ship, the effective weight changes, and that brings about a change in the draught. Fluctuating draught lines may adversely affect the stability and manoeuvrability of the ship structures. And most importantly, we can never let the propeller, rudder and bulbous bow to rise above the surface. Here comes the importance of ballast. Ballast by definition is any solid or liquid that is brought on-board a vessel to increase the draught, change the trim, and regulate the stability or to maintain
the stress load within acceptable limits. With the introduction of steel-hulled vessels and pumping technology, water became the perfect choice to be used as ballast, as it is easily pumped in and out of ballast tanks, possesses nearly no stability problems and is available all over. The process of ballasting is basically loading water from one port and discharging it in the other as per the requirement. Even though the planet is blue all around, the water is not the same everywhere and so is the ecosystem. So while ballasting a ship, the water is being taken from one ecosystem and mixed with some other. This intermixing of untreated ballast water has a lasting impact on the environment of the native area. Along with water there are a plethora of aquatic species present, including all sorts of bacteria, micro algae, and various life stages of aquatic and plant and animal species. Species are considered alien
if they are not native to a particular ecosystem. Under optimum conditions the alien species can survive and populate. Once they become dominant, the native species find it difficult to survive and may get extinct. This breaks down the existing biodiversity of the place; impacts coastal industries, fisheries, and the local lives, be it economy or health. The treatment of ballast water is hence a necessary requirement in an efficient design of a ship, especially in the current era of green shipping. Ballast water treatment IMO’s “International Convention for the Control and Management of Ship’s Ballast Water and Sediments”, has made the implementation of ballast water treatment systems a priority. A practical method to minimize the introduction of alien species from the ballast water discharge is Ballast Water Exchange.
The coastal water which can be fresh water or salt water is flushed out of the tanks with open ocean water generally 200 Nautical miles away from the nearest land, atleast having a depth of 200m. It is expected that the temperature and the salinity differences would result into less chances of the survival of the added organisms. However it has been determined that this method does not provide adequate measures to prevent damage taking place in the ballast vessel from the species. Ballast water treatment technologies ,the technology for treating ballast water can be either port-based or ship-based, the latter being the more viable option. Port-Based treatment: This treatment requires that the ballast water be transferred to an offshore facility and then the necessary treatment is carried out. Valdez Marine Terminal, Alaska has one kind of ballast water treatment facility for decades to remove residual hydrocarbons from dirty ballast water. On board treatment: Currently, the on-board technologies available for ballast water treatment can be categorized based on their primary mechanism for inactivating the organisms; namely, Mechanical, Physical and Chemical. Mechanical Systems: • Filtration: Filtration is an effective method against sediments and various types of organisms. The physical separation can be done either during loading ballast or during the voyage. In this method the particles are removed with disk and screen filters during ballast loading. These filtration systems can create pressure depressions and a decreased
flow rate due to a resistance in the filter elements. • Cyclonic Separation: Cyclonic Separation is used for those particles with a specific gravity greater than that of water. The particles get separated from the water due to centrifugal forces. It is normally done using hydrocyclones. • Electro-Mechanical Separation: A flocculent is added that attaches to organisms and sediments. They are magnetically separated and then filtered. Physical Disinfection: • Ultraviolet Light: UV systems are the most popular option at present. UV radiation is used to attack the organisms outright or to destroy their ability to reproduce. The efficiency depends on the turbidity of the ballast water as this can limit the transmission of the UV radiation. The UV systems are suitable for any vessel but preferably for those who do not take in much ballast water and have flow rates of upto 1000 cubic metres per hour like RO-RO vessel, container ships, offshore supply vessels and ferries. • Cavitation/Ultrasounds: The cell walls of the organisms are disrupted by high frequency noise. This high frequency noise is created when cavitation bubbles are formed in venture pipes or slits collapse. • De-Oxygenation: Inert gases such as nitrogen are bubbled inside the ballast tanks removing the dissolved oxygen in the water and they lower the pH levels, thereby killing the living organisms. Other than killing the aerobic organisms,
this method can also benefit in corrosion prevention. De-oxygenation can require a prolonged period in order to render the organisms harmless to the water. Chemical Treatment: • Disinfecting biocides: Pre-prepared or packaged disinfectants are designed to be dosed into the ballast flow and kill the living organisms by chemical poisoning or oxidation. These systems are generally combined with filtration. Typical biocides are chlorine, chloride ions, chlorite ions, chlorine dioxide, sodium hypochlorite and ozone. Ozone is applied during the ballast pumping process at uptake or discharge. This method is generally used on vessels with larger capacities and flow rates such as tankers and bulkers. Residual biocides in the ballast water must meet ballast discharge standards which later may require neutralization techniques. • Electrolytic Chlorination: Electrolytic chlorination has a share of about 35 percent in the market of ballast water treatment. Electric current is passed through the ballast water flow in an electrolytic chamber, generating free chlorine, sodium hypochlorite and hydroxyl ions, causing electrochemical oxidation through the creation of ozone and peroxide which generate nascent oxygen. This method is limited in effectiveness to seawater having a certain amount of salt and could also create unwanted residuals. This method is suited for vessels with large ballast tanks with high volume rates of upto 8000 cubic metres per hour.
UNDERSTANDING STABILTY BETTER
DAMAGE STABILITY SOUMYA SAMEER
INTRODUCTION Centuries ago when the aboriginal adventurists ventured into the sea in their primitive rafts to experience the thrill of moving across the waters, it didn’t take them much time to understand the hazards bounded with the feat. Disasters happened, their boats crumbled, capsized, sank, losing their lives. Using trial and error as their implements those craftsmen gradually developed expertise. Since the advent of 18th century mathematical and scientific approach has been taken in order to estimate and anticipate the hazards beforehand. It is necessary to ensure that if any mishaps happen such as fire, flooding, explosion, structural damage, the ship can sustain a substantial level of damage and enough time is there to prevent any immediate catastrophe and steps can be taken to mitigate the consequences and render counter-actions available.
Damage Stability: The Term The term damage stability deals with the ability of a ship to float in water and regain its upright equilibrium position, when some sort of structural damage has occurred. Generally following an accident, the damage is hull fracture leading to flooding of ship compartments. If so many compartments are flooded that there is not enough buoyancy available to keep the vessel afloat, the ship may sink. Another critical scenario due to hull breach is ship capsizing due to loss of transverse stability as it can happen very quickly. The disasters of Herald of free enterprise and Estonia are few such instances. How do ships get damaged? Surface ship damages were havoc to the economy of the nation due to their high cost. This made the naval architects study the factors that contribute to ship damage in the sea.
Some are enlisted below a. Collision b. Grounding c. Poor design or structural failure d. Natural Calamities After the naval architects studied the reason for ship damage, they tried to quantify the damage and tried to design the ship, keeping in mind the survivability of the ship in case of damage. They tried to incorporate the damage stability analysis of a ship in its design phase such that no or less failures are experienced at the time of operation. This made the job of the naval architects pretty difficult and damage stability analysis came into picture. The damage stability analysis included • Quantification of the behavior of the ship when damaged in case of a failure or accident.por • Design aspects to prevent or restrict the havoc caused by the failure.
The two approaches of Damage Stability Analysis To assess the behavior of a ship after some damage, two methods are considered: â&#x20AC;˘ Deterministic damage stability â&#x20AC;˘ Probabilistic damage stability
deterministic damage stability This is a traditional method of assessment of stability of a ship when it is flooded. In this process the ship is divided into several subdivisions along its length with the help of transverse watertight bulkheads. Now the stability of the ship is calculated when one or more compartments get flooded due to breach of hull. The changes in draft and stability when a compartment becomes flooded due to damage can be investigated by either of two methods: 1. Lost Buoyancy method: The damaged compartment(s) is considered open to the sea and therefore, does not contribute to the buoyancy of the ship. So, the lost buoyancy must be compensated by sinkage of the vessel and the moment due to change in LCB of the vessel is manifested through the heel or trim of the vessel. The assumptions considered in this method are that the flooded compartment does not provide buoyancy anymore and hence, there is no change in displacement or KG of the vessel and no free surface effect is observed. 2. Added Weight method: This method considers that water ingresses in the damaged compartments upto the new water level and the weight of the ingressed water augments the displacement of the vessel that is compensated by the sinkage of the vessel. Consequently,
the KG of the vessel changes due to weight of ingressed water and Free Surface Effects has to be taken into account, if the compartment is partially filled with water. The weight added shifts the CG of the vessel that might lead to list or trim of the vessel. Thus the two methods act as a twofold assessment of the damaged condition of a vessel. It is actually a good practice to verify the result of assessment of the damaged condition of the vessel by the complementary method. Both methods will give identical answers for final draughts, trim and righting moments, despite different values for GM. However, IMO/SOLAS recommends the use of Lost buoyancy method for all calculations.
Deterministic damage stability As we discussed, in deterministic approach the hull is internally subdivided to increase the factor of safety of the vessel in case of hull damage. Now this subdivision is not arbitrary. It takes a lot of study and analysis balancing both economic and safety needs of the vessel before the designer fixes the subdivision of the vessel. In this approach the length of this compartment is to be calculated such that if this compartment is flooded, the ship will sink to a point where margin line is just submerged. This is the floodable length at a point along the length of the ship. The subdivisions accordingly resist flooding in damaged conditions to the safest limits. Floodable Length is an important parameter that is taken into account here. It is defined as the maximum length of the compartment that can be flooded such that the draft of the ship remains below the margin line. Thus, maximum division of bulk-
heads is the best solution. But, other factors such as minimum required size of hold, improper cargo stowage, and more number of required outfitting or increased steel weight hinders the possibility to some extent. Thus, optimizing the safe limits of floodable length to the minimum required length of watertight compartment is done in most cases. Floodable length Curve: A ship should not sink if any one compartment is breached and flooded is the idea behind developing the floodable length curve of the vessel. The floodable length closer to the midship area is larger compared to the ends of the vessel since the flooding of the midship compartments are accompanied with parallel sinkage whereas the flooding of the end compartments are accompanied with sinkage and trim that augments the chances of the waterline touching the margin line of the vessel. Therefore, the floodable length varies along the length of the ship and its variation is obtained by vertically plotting the floodable length along the shipâ&#x20AC;&#x2122;s length. Also the floodable length along the length of the ship is a function of the permeabilities of each compartment. More is the permeability of the compartments, more will be the water ingress in case of a hull breach and as a result lower will be the floodable length at that point along the length of the ship. Factor of subdivision: The FOS is the measure of the degree of factor of safety availed while designing the vessel in the state of damage. As per the definition of floodable length it is the length of the compartment which when flooded, the waterline will just touch the marginline. Now if a vessel is designed with each watertight compartment length
Focus on solving the problems in the industry
Raunek Kantharia is the Founder and Chief Editor of Marine Insight. He is a marine engineer turned maritime writer and professional blogger. After a brief stint at the sea, he founded Marine Insight in 2010 to raise awareness about the maritime industry and the life of seafarers. Apart from managing Marine Insight, he also writes for a number of maritime magazines and websites. In an interview with Kushagra Gupta and Soumya Chakraborty of Learn Ship Design, Raunek shares some insights from his entrepreneurial experience and perspectives on the impact of digitalisation on maritime information and education sector.
How did the idea of Marine Insight emerge? What compelled you to pursue this idea? I was a freelance writer for many years before I started Marine Insight. Subscription-based print maritime magazines and periodicals were prevalent during that time. However, they had a limited reach and targeted only a specific section of the industry. Being a maritime professional with considerable years of experience in the publishing industry, I understood what kind of information maritime professionals were ac-
tually looking for. I have always been an ardent supporter of digitalisation and wanted to help maritime professionals globally. Marine Insight was born out of the purpose of assisting people around the world by providing informative solutions to common problems using a digital platform.
And now, Marine Insight is the worldâ&#x20AC;&#x2122;s most read maritime information website. Was this your ultimate objective when you founded Marine Insight or are there bigger plans now?
We started Marine Insight with the sole goal of assisting as many people as possible. Making it famous was never part of the plan. We just wanted to provide solutions to issues we personally experienced in our careers and also to offer assistance to those who came to us with problems.
How have you seen your reader-base evolve over the years?
Do you think that there is a gap between industry expectations and curriculum design in academia? If yes, what are some of the solutions?
When we started out, we only targeted young students and mariners who are fresh in their careers. Many experienced and senior maritime professionals joined us on the way, providing important insights from their experiences and knowledge. This helped us to reach a wider segment of the industry.
Can you tell us about your experience as a Marine Engineer?
A Q A
I have done three shipping contracts as a Marine Engineer. My partner Mr Anish Wankhede is a 2nd engineer with extensive sailing experience. Which types of ships did you work on? What is it like to be out at sea? How does it feel? I have mainly worked on container ships. Working at sea is an experience in itself. You got to be mentally and physically strong. It is definitely not an easy life out there but it is surely one of the best for a thorough professional and personal development.
What is your perspective on the past, present and future of the maritime industry?
The maritime industry is the backbone of global trade and economy. As countries around the world continue to develop, the need for an efficient and low-cost maritime transport will always stay and in fact, continue to grow with all the latest technological advancements.
Absolutely. There is a huge gap and many experienced and expert professionals have addressed this issue through our platform. Marine Insight is also working together with people from around the world to seek a solution for this ongoing problem. The maritime education sector is yet to completely adopt advance simulation and digital learning. We are actively participating in something called the â&#x20AC;&#x153;Global Onboard Training Initiativeâ&#x20AC;? to address this issue.
Coming back to Marine Insight, how do you think digital marketing and emerging technologies will enhance reader experience?
The future is digital and I guess everyone will agree to that. It is all about the convenience of the readers. Marketing itself is very dynamic and digital marketing is in constant change. It is therefore very important to adapt early to the latest technologies to reach a wider audience.
Please share with us your experience as an entrepreneur. It has been a long journey. You always have to be on your toes. There is no room for complacency. You have to be a quick learner and quicker at implementation. There will always be ups and downs, but it is only during the downs that your real
entrepreneurship skills will be tested. Focus on your strengths and donâ&#x20AC;&#x2122;t shy away from taking help. Have an open mind and soak in as much knowledge as possible. As an entrepreneur, it is very important to have a purpose and to stay a student for life.
What are the opportunities for budding entrepreneurs in this industry? What would be your one advice to them? There are several opportunities in this industry. My only advice for budding entrepreneurs will be to focus on solving the problems in the industry. Believe in your idea but take analytical decisions. Do extensive research before pursuing a purpose. Once you are confident, give your hundred per cent and leave no stones unturned to realise your goals.
Do you have any message for budding writers and editors in the maritime industry?
Write on issues that are plaguing the industry. Let your voice be heard. Try solving common problems of the industry. We as writers and editors can do a lot in finding solutions to ongoing problems and raising voices against unfair practices.
Do you have any other message for our readers?
We would love to hear feedback from the readers as to what and how can we improve Marine Insight to serve them better and in a more user-friendly way.
WHY AND HOW
HULL FAIRING AND
DEVELOPMENT SUDRIPTO KHASNABIS
39 How would you design a ship hull with all its curvatures and characteristic intricacies such that it doesn’t become too complex for production? Obviously, you would search for ways to break it down to smaller manageable pieces which can be easily processed in the workshop as workshop has to find out practical ways to create a scaf-
REMEMBER HOW YOU MIGHT HAVE CREATED MANY THINGS OUT OF PAPER FOLDING SUCH AS ANIMALS, FLOWERS ETC. BACK THEN YOU HAD ACTUALLY LEARNT THE CONCEPT OF DEVELOPMENT OF 3D DIMENSIONAL OBJECTS STARTING WITH 2D LAMINAS (E.G. PAPER). NOW, LET US THINK OF SOMETHING QUITE COMPLEX IN THREE DIMENSIONAL TERMS BUT QUITE LARGE IN SIZE.
YES, I’M TALKING ABOUT A SHIP’S HULL.
folding / loft for bringing the desired hull shape to reality. The concept of development of the hull plating for production is a very relevant one even in today’s CAD (Computer Aided Design) era. The ship hull is designed on a software platform which enables the user to visualise the 3D problem (Representation of the three-dimensional hull lines as 2D equivalents in various sections
i.e. the sheer plan, half breadth plan and the body plans) in an intuitive manner. By making changes in any one of these sections, the user effectively manipulates the lines in 3D changing the other sections instantaneously. Given this great advantage, we come to the actual problem of fairing a hullform while keeping the curvature developable with plating. Fairing often tends to get many defini-
tions across literature, but it effectively serves certain purposes: • Superior hydrodynamics: optimal vessel speed, low resistance, increased fuel efficiency, manoeuvrability, etc. • Aesthetics: appeal to the human senses, functionality after life cycle (e.g. conversion to resorts, display in museums, etc.) However well built a ves-
and fairing job done reflects the shipbuilder’s attention to the tiniest of details and is often a matter of pride for them. Finishing and fairing are often considered among the finer arts of shipbuilding. For a moment, think of you having the job of producing a smooth surface out of a body with a coarse surface, you have the option of removing away the high points on the surface until you reach a low level (something often done with
The following images have been rendered using a licensed version of Maxsurf Modeler Advanced, an industry standard application from Bentley Engineering. wood), also you have the option of adding material to reach a higher level to maintain evenness (paints and surface applications) you could also take some material from the higher planes and deposit it on the lower planes to reach a degree of smoothness. Shipbuilding employs paint, surface preparation, and many other techniques to achieve the level of finishing of modern day standards. A ship hull is composed of numerous steel plates which are rolled or bent to give the characteristic shape at some section. Take a look here at a ship’s shell expansion plan given
This represents the developed surface of the plating used (at plate level) in the manufacture of a vessel and often gives an estimate of the steel to be used in manufacturing the ship. But since the development of a shell expansion plan comes quite later in to the ship’s design cycle, the designer is faced with the problem of ensuring that the hull surface is fairly developable. This is where software comes in. Advanced ship design productivity suites like MAXSURF or DELFTship provide fairing modules for this. The principle on which these are based is that the curvature of a certain ‘patch’ or element in the hull skin can either stand for single/multiple or positive/negative curvature for the collection of points within it. Certain typical representations of such curvature are as follows: 1.) In ship designs, the transverse curvature is particularly higher than the longitudinal curvature and so it might be helpful to exaggerate the
transverse curvature in view to aid the designer in finding out the inconsistencies (if any) in the fairness of the model. For this reason, some programs allow this to be represented as one of the rendered forms. 2.) Another important tool allows
us to modify particular waterline contours based a graphical representation of the curvature along the contour, often called curvature porcupines. Notice the radially outward emerging lines in grey? The height of these lines are proportional to the amount of curvature inherent at the location. Even a slight change in control point position alters these greatly and hence offer a better intuitive experience of fairing. In the event an outward emerging porcupine ends up inside the waterline, the section indicates a hollow in the hull surface and needs rectification. The porcupine curve which runs along the porcupines should be fairly smooth, if not, then there are options to change the stiffness of the control points used in the model.
It is not that these programs never existed, but they have become better at doing their job and save time.
3.) One popular and simple way of evaluating the fairness is by using the rendered hull using lighting highlights. This shows how light would bounce off the surface of the hull around the hull and is often useful in creating promotional and non-technical content too. This tool entirely depends upon the userâ&#x20AC;&#x2122;s perception and can only be used for major bumps/irregularities. 4.) Some programs offer additional tools for evaluating curvature in a more quantifiable manner. A popular one among these is the Gaussian Curvature rendering mode. Here the product of the principal curvatures at a given point are represented. If the
curvature is on the positive side, it implies that the longitudinal
and the transverse curvature are in the same direction (tends to a bluish/greenish tinge) while the other locations where negative curvature is present, the colour progresses from yellow towards red (points of oppositely oriented transverse and longitudinal curvature). The greener areas represent fair locations and are completely developable (helpful for what was talked about earlier) implying they are either flat or cylindrical. 5.) Now, we come back to one of the most fundamental ways of observing the fairness of a 3D model. CAD programs use 3D
geometry where often complex shapes (like a hull) are repre-
sented using control points. And to an experienced designer, the orientation of the control planes resulting from these points is enough to suggest if the model needs additional
fairing work. These were some of the more hands-on fairing methods quite frequently used within a shipâ&#x20AC;&#x2122;s design cycle. There has been a lot of research going in to developing automated algorithmic approaches to solve the problem of fairing mathematically, (and understandably) these techniques are often based on the properties of curvature and their representation. Such programs usually tend to solve non-linear equations and sometimes computationally intensive. It is not that these programs never existed, but they have become better at doing their job and save time.
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arvels and wonders of engineering and technology, ships are just the basic necessity for the global economy. A world without ships is just unimaginable right? Ships have been in use for centuries. Thousands of ships are ordered in a year. Currently there are over 50,000 merchant navy vessels. All this makes one wonder, don’t ships get recycled or thrown away? The answer to this question is Shipbreaking. Shipbreaking is done in ship breaking yards, where these giants, once ruling the seas come to die. Shipbreaking is a multibillion dollar industry that thrives over the regions of India, China, Bangladesh and Pakistan. It is estimated that these 4 nations contribute to about 94.9% of the shipbreaking that is done throughout the world. Alang in Gujarat and Chittagong in Bangladesh are the most famous ship break-
ing yards in the world. Alang is considered to be the largest ship breaking yard in the world where over 50% of the world’s vessels come to be dismantled. Next in the line is Chittagong yard, lying about 18 miles to the north of Chittagong. This yard handles about 20% of the total ships in the world and accounts for almost half of the steel in Bangladesh. Shipbreaking is economically very useful as it reduces the amount of energy and labour in the steelmaking process. This reduces the demand for mined iron ore. Let’s see how this industry works. The cost of disposing the ships off cleanly is much higher than scrapping them, so Western owners simply sell their vessels for scrap and Indian owners make a profit by reselling the steel and other things inside the ship at low prices. A ship breaker buys the ship for a few million dollars depending upon the size and quality of the ship.
There is usually a middleman who connects Indian buyers with foreign sellers. The ship breaker then takes a loan from a nearby bank often at a high rate of interest only to pay it back within 6 months once the vessel is scrapped and goods are sold. Cheap labour comes as a boon. Poor people from all across the country flock to these shipyards to earn a living. Ship breaking is done at a very minimal cost. Labourers break the ships using their bare hands. These yards have basic equipment missing and workerâ&#x20AC;&#x2122;s safety is nothing but a dream here. Most workers donâ&#x20AC;&#x2122;t even get safety goggles and their wages are as low as $1 per day. There are different classes of ship breakers, supervisors, cutters, loaders-unloaders and carriers. Women are employed as carriers and a lady carrier earns about Rs.40 a day while a male carrier earns about Rs.50. The most elite ship breakers are the people using gas cutters. These people are experienced and have an idea about the insides of a ship. They are the ones who start cutting up the ship from inside and face major threats. Most ships, when they come in, have many poisonous or inflammable gases and oil in different parts of the ship. With no equipment to measure the threat, people tie a string of chickens and put it inside the container. If the birds come out alive, people move inside and start their job. Still hundreds die in the job and their families are poorly compensated. The most common cause of death here is gas explosion. Many die
when huge ship parts fall on them. That apart, the beaches are always covered with toxic substances that arise from ship breaking. Mud and oil mix together to form a thick grey slug and people have to constantly expose themselves to it. Temperatures rise to about 50 de-
ing for the ship breaking yards. The percentage of people with disabilities in the Chittagong area is much higher than the whole country of Bangladesh. People deal with toxic substances like asbestos and lead(Pb) on a daily basis. Safety limitations for lead exposure have already been crossed and people suffer from poisoning every day. Bangladesh has 79,000 tonnes of asbestos, 240,000 tonnes of PCB and 210,000 tonnes of ozone depleting substances. Even though a law exists in Bangladesh known as the Labour Law act of 2006 which imposes certain restrictions for Labour grees Celsius in the yard. WorkSafety and ensures labour safety, ers have to travel from one part there is no one to implement of the ship to the other on thick these laws. Corruption and polcables, which if snaps, can slice a man in half.it is a necessary evil. itics is killing thousands in BanAn estimate says that majority of gladesh and India. Shipbreaking is a story where, a thousand the workers are below 22 years innocents die every year to save of age and most of them are illiterate. Local estimates say that a nation. Sometimes one does around 1000-2000 people have put up a question, is shipbreaking worth it, What to do? died in the past 30 years work-
is shipbreaking worth it, What to do ?
PRO PUL SION
ne of the most important and key areas of design for any movable vehicle is its propulsion. When it comes to ships the task becomes indeed more challenging with respect to the dynamic environment in which the ship sails. Other modes of transport like land have the benefit of high value of ground friction to provide better manoeuvrability .Even aircrafts cruise high above in the stratosphere to avoid the extreme conditions in the troposphere. But the same cannot apply to marine vehicles which are confined to face the dynamics of the vast blues. Keeping a number of factors in mind the propulsion systems of the ships are designed. Since the early modes of propulsion requiring oars to the steam engine to the modern azimuth and cyclorotor
propellers every aspect of design has been carefully scrutinised according to the technical expertise and resources available at that time. The shape of oars as aerofoil sections altering the flow between the front and back faces to provide thrust is a testament to the engineering and technical expertise available hundreds of years ago.
are also coming into play gradually and extensive research is going on to develop advanced technologies such as fuel cells , superconductivity and magneto-hydrodynamics and harness their full potential.
A wide range of machinery from those relying on wind in sailboats to steam engines to steam turbines to the invention of the popular diesel engine to gas turbines to the modern day nuclear energy have all been used for propulsion in different cases according to the technical feasibility and expertise at that period and specific requirements. Unconventional and renewable sources such as solar energy , wind energy and wave energy
Open Water Characteristics of a propeller To determine the intrinsic performance characteristics of a propeller the propeller is operated in undisturbed or open water. This is done to obviate the effects of the ship and the disturbed flow around it falling on the propeller. The characteristics measured are the variation of thrust , torque and efficiency with the speed of advance and revolution rate of the propeller in open water.
This article focuses upon the open water characteristics of a propeller and the experiment carried out to get the same.
maximum values of KT and KQ occur at J=0. This physically represents the bollard pull condition in which the maximum pull of a tug is estimated or it may represent the static condition during the dock trials of the ship. It corresponds to the 100 percent slip condition wherein VA = 0 and the propeller blade section has the highest angle of attack equal to its pitch angle.
As it is impractical to achieve these characteristics with a full sized propeller , a model propeller is made which satisfies the required conditions in which the quantities measured can be extrapolated to the full scale. The laws of similarity govern these conditions and are applicable both for open water and behind conditions 1. Geometrical Similarity: Every linear dimension of the prototype bears a constant ratio to the corresponding dimension of the model. In the case of propeller one may consider the propeller diameter as the characteristic linear dimension. 2. Kinematic Similarity : This requires the ratio of any velocity in the flow field of the full size body to the corresponding velocity in the model be constant. The constant ratio is equivalent to the corresponding advance coefficients being equal. JS = JM 3)Kinetic (Dynamic Similarity) : It requires he ratios of various forces acting on the full size body be equal to the corresponding ratios in the model. It involves three ratios which ultimately correspond to the Reynolds number , Froude number and the Euler number.
Open Water Characteristics The advance coefficient J , the thrust coefficient KT , the torque coefficient KQ and the open water efficiency ɳo are all plotted on the same graph to determine the open water characteristics of the propeller. KT,KQ, ɳ are plotted as functions of J. The KT–KQ diagram sheds light on some significant conditions encountered during the test. Salient Features 1. The graph clearly depicts the
2. The value of J at which KT is equal to zero represents the condition where the resultant velocity is directed along the no lift line. In this case the thrust developed is zero( provided the negative contribution of the drag is neglected). This condition physically represents the feathering condition/condition of zero slip. 3. At KQ =0 , the propeller revolves by virtue of the water flowing through the propeller disc and the condition is called wind-milling. 4. For maximum efficiency the propeller operates between zero and 100 percent slip conditions and the max value of efficiency occurs at an effective slip ratio lying between 10 and 20 percent. 5. The value of ɳo falls sharply for values of J greater than the one corresponding to max ɳo . Four Quadrant Characteristics In certain circumstances the propeller is reversed or its direction of rotation is changed so as to alter the ship motions to manoeuvre it accordingly. For example,The propeller may be operated in the reverse direction to cause astern motion of the ship or to decelerate it when the ship is going forward.
Similarly for a ship going astern the propeller maybe operated in the forward direction to stop or make it propel forward. Corresponding to these conditions one may obtain the four quadrant characteristics of the propeller w.r.t to the speed of advance VA, the revolution rate of the propeller (n ; taken as positive for forward thrust and negative for astern thrust). When n=0 , the coefficients J, KT , KQ become infinite and hence are not suitable for representation. By replacing J with the advance angle Î˛ , KT by CT and KQ by CQ one may plot the four quadrant characteristics. Open Water Experiment As previously stated it is impractical to determine the open water characteristics with a full size propeller, a model propeller is made satisfying the required conditions of similarity so that the results can be extrapolated to a fair degree of accuracy. Certain key factors are to be kept in mind so as to simulate the actual flow conditions around the ship propeller. The model propeller is made as large as possible to the extent of its compatibility with the propeller dynamometer available.
This is done to achieve a high value of Reynolds Number and make the flow turbulent. The propeller surface is made of matte finish with the leading edges of the blades roughened. The experiment is carried out by attaching the model propeller to the dynamometer (for measuring the thrust and torque ) fitted in an open water boat. The shaft length is extended sufficient enough to ensure the flow around the propeller is undisturbed due to the boat. To eliminate hub vortex cavitation a fairing cap is provided at the forward end of the propeller boss. The boat is ballasted to the required draught ensuring the model propeller is completely immersed. The experiment is conducted by towing the open water boat at a steady speed whilst the propeller is running at a constant revolution rate. The model propeller is run at all speeds of advance at a constant revolution rate with VA , n , T , Q measured for each run. VA is varied in steps from zero to the value where the thrust just becomes negative. Certain corrections are made to get the extrapolated results quite accurate. ITTC has laid down certain guidelines for the experiment. Thus propulsion is a key area of
design for any vehicle and for self -sustaining cities such as ships sailing on the vast blues it becomes imperative to scrutinise each and every aspect of it and all related work to be carried out with due diligence and punctiliousness. The efficiency of the propeller, the effects of cavitation and the wake distribution around the hull are some of the important factors to be kept in mind while designing the propulsion system. The main engine is the most important and costliest part of a ship and its selection should be based on the type of propulsion required. Newer technologies are coming for faster propulsion in oceans even in rough seas while maintaining good efficiencies. This will be a turnaround for the global trade as trading becomes even more faster and seamless with faster and efficient ships. The propeller and the hull should be in perfect synergy to achieve the required performance characteristics. A very good propeller which is incompatible with a hull will be rendered ineffective and perform below its efficiency and will be economically not feasible. Resistance of the hull and propulsion go hand in hand for designing this system as the behaviour of the hull also has to be taken into account. This is dealt separately in the behind condition characteristics of the propeller in which the flow coming onto the propeller is disturbed by the hull. The characteristics of propeller behind a ship will be explained in the upcoming article in the next issue.
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SHIP UNDERWaTER NOISE SIGNATURES G.V.V. PAVANKUMAR
ound has always been an important form of energy to understand the ocean in a better way. Most of the underwater applications are carried out using sound. Sound has always been a disturbance that propagates through an elastic medium due to alteration of pressure. The speed of sound in water is 4.3 to 4.4 times greater than that in air. The acoustic waves underwater are used to detect, locate, measure and transmit applications. The transmissibility of sound is considerably affected by the frequency of the noise source. In general, high frequencies in water are strongly attenuated with increasing distance from the source, whilst the lower frequencies tend to travel further, and are therefore considerably more serious from the ship radiated noise view point. Shipping traffic radiated noise has always been a major factor affecting the ocean noise levels. These anthropogen-
ic sources over the last two decades have increased the ambient noise levels by about 10 dB as per International Quiet Ocean Experiment (IQOE). These low-frequency noise levels have many effects on to the marine fauna hindering the mammalâ&#x20AC;&#x2122;s activities like communication, navigation etc. The low-frequency signal also propagates long distance ,affecting over a large region. The self-noise levels impose limits to the achievable performance when it exceeds the ambient noise levels. The sources of noise radiated from the ships being propeller noise, machinery noise, flow noise, transient noise and activity noise as indicated in Figure 1. The spectrum of the noise radiated by a ship presents a continuous broadband background, the level of which usually increases with ship speed. At lower frequency, the wide-band noise is rather constant or even deceasing, and becomes superseded by the narrow-band components associated to rotating devices such as engines or gearbox.
Instrumentation A hydrophone system integrated with data acquisition system was used to carry out underwater sound pressure level measurements. The handheld linear PCM recorder is used for data acquisition. Fast Fourier Transformation spectral analysis program is used to
^FIGURE 3 Indicating the ship radiated noise levels over the ambient noise levels
post-process the time domain signal to the frequency domain in 1/12 octave band. The post-processed spectrogram is used to identify the various excitation frequencies. Shipping noise levels The underwater sound pressure levels in dB re 1 ÂľPa units indicated that there is an increase in the sound pressure levels due to the ship movements. The major contribution is mainly in the lower frequency region as indicated in Figure 2. The increase is mainly due to the sources as discussed in the introduction section. The continuous movement of the ship FIGURE 1 Major ship sources which generate underwater noise>.
^FIGURE 2 Indicating the ship radiated noise levels in the ocean affects the background noise levels of the region. It is noticed over the years that the ambient noise levels of the oceans are increasing with shipping traffic ,which being one of the major contributor as indicated in Figure 3. These low frequency noise levels also effect the ocean environment and the marine fauna. Most of the marine life use sound as the major form of energy for their daily activities. The increase in ambient noise levels have severe effects on the living condition and bring about biological changes in their activities. Conclusion Considering the environmental impact assessment, there is a need to reduce the ambient levels of the ocean. Shipping traffic being one of the major contributors,there is also a need to understand the ship radiated noise levels so that technology can be developed to attenuate the radiated noise levels at the design stage. At International levels , regulations to mitigate the ship radiated noise levels have been established by IMO and procedure for measurement of underwater ship radiated noise was developed by ISO. Moreover, the field is identified as a knowledge gap area to carry out more research in developing ship
IT IS ALL ABOUT SAFETY AT BEACHES
Dr. K.V.K.R.K Patnaik
eaches are the most attractive destinations to most of the people all around. Beach tourism is one of the worldâ&#x20AC;&#x2122;s largest industry and promising huge potential in the income generation to most of the maritime countries. It is widely accepted that the beaches fascinate us ,however proper precautions need to be taken to experience safe and pleasant swims along the beaches. India is having a very long coastline of about 7500 km and is embedded by very beautiful locations. Compared to east coast of India, west coast beaches are carved with natural landscaping and said to
be safe for swimming. This can be attributed to the swells that are originating in the Southern Ocean and propagating towards Bay of Bengal and Arabian Sea.The east coast of India faces these waves directly resulting in the steep and strait beaches. Hence these east coast beaches are always dangerous to swim. However the west coast beaches do not face the southern ocean waves directly, therefore these beaches are less affected by the wave action and could maintain the natural landscaping and gentle steepness. Apart from the wave action on beaches, there are other coastal processes acting along the beaches namely formation of long-
shore currents, erosion/deposion, sea level variations and tidal action. Hence upmost care need to be taken while you dare to venture into the beaches. The formation of long-shore currents are due to the fact that the waves bend while they approach to the shore and they become parallel to the shore before they break. This phenomenon is called wave refraction. The reason behind this bending is due to the changes in the bathymetry. After the wave breaking ,the energy is dissipated in the form of sound, sediment erosion and generation of currents.
The currents formed because of the wave breaking are called longshore currents. The current direction depends upon the orientation of the wave approach to the shore and the shape of the coast. Waves may converge and diverge based on the shape of the coast. Waves approach towards a bay diverge while convergence takes place when waves approach towards headland. This convergence and divergence phenomenon results in the formation of opposite long-shore currents. When two opposite long-shore currents encounter each other,it
results in the formation of flash and very narrow jet like current heading towards the sea. This phenomenon is called the formation Rip currents. These rip currents are very dangerous to swimming and many drowning cases are associated with these currents worldwide. Prediction of Rip current formation is still under initial stage. However, identification of formation zones of Rip currents can be possible by analyzing the size of the sediment and from the satellite pictures. Proper precautions need to be taken by the local government authorities to safe
guard their visitors by indicating the dangerous zones for swimming and mentioning the chances of formation of Rip current zones. It is very difficult to swim against the Rip current even to the professional swimmers. Hence persons caught in the Rip currents need to swim parallel to the coast and try to escape from the narrow current which flows normal to the shore and into the sea. Following the precautions at the beach, one can enjoy the beaches.
he foremost criteria which a naval architect decides in his mind for designing a new ship is to estimate the weight of a ship. The weight of a ship or displacement is the weight of volume of water that the ship displaces and it is divided into 2 parts:
LIGHTWEIGHT: This is the weight of the ship itself, when it’s completely empty (consisting of steel weight, wood and outfitting weight, and the weight of machinery components). This value will change over the years. DEADWEIGHT: This is the weight that a ship carries. It comprises mainly of fuel oil, fresh water, stores, lubricating oil, water ballast, provision and stores, crew members or passengers and cargo. This value will vary, depending on how much the ship is loaded between light ballast and fully loaded conditions. WATER DRAFT: This is the vertical distance from the waterline down to the keel (lowermost plating of the hull portion of a ship). Draft measured from top of keel is known as “draft moulded” while draft measured from bottom of keel is known as the “draft extreme”. There are typically three types of length dimensions used for different ship calculations.
LBP or LPP (LENGTH BETWEEN PERPENDICULARS): It is the distance measured between the fore and aft perpendiculars along the summer load waterline. LOA (LENGTH OVERALL): It is the distance measured between the extreme points forward and aft and is measured parallel to the LBP. The importance of LOA is very much obvious, generally when small ships with bowsprit are docked in marina slips (small ports for handling yachts and small boats) where we need to account for dock walls or bulkheads.
LWL (LENGTH ON WATERLINE): It is the length of ship on waterline at which the ship happens to be floating.
cally downwards and the force is equivalent to the weight of the body. It is generally denoted by G.
FREEBOARD: It is the distance measured from the load waterline to the uppermost/free deck of a fully loaded ship. It is generally measured around the midship section of the ship at the side of the hull. The deck below which all the bulkheads are made watertight compulsorily is known as the freeboard deck.
CENTRE OF BUOYANCY: The centre of buoyancy of a body ,is a point through which the buoyancy force(up thrust) is assumed to act vertically upwards and the force is equal to the weight of water displaced by the body. It is the centroid of the underwater volume. It is denoted by B.
SHEER: It is a measurement of the rise of deck towards the bow/stem and stern with reference to the level of deck at mid-ship. The forward sheer is generally greater in value than aft sheer to protect forward anchoring machinery parts from the impact of waves.
HEEL: A ship is said to heeled when it is inclined by an externally applied force, for example- by the action of waves or winds etc.
CAMBER: It is also referred to as the upliftment of the deck when going from the sides (port and starboard) towards the centre of the ship. Decks are generally cambered to allow any accumulation of water to drain off through the sides very easily. Before the ship is built the most important factor which comes into account, is the ship’s stability which deals with how a ship behaves at sea, both in still water condition and waves. Stability calculations concentrate on several factors such as centre of gravity, centre of buoyancy, metacentric height, centre of pressure, moment to change trim etc. CENTRE OF GRAVITY: The centre of gravity of a body, is a particular point through which the gravitational force is considered to act verti-
LIST: A ship is said to be in list condition when it is subjected to internal forces within the ship, for instance when it is subjected to shifting of weight in transverse direction within the ship and thus having a fixed angle of heel. METACENTRE: If two verticals are drawn through the centre of buoyancy for two or more consecutive angles of heel ,then they coincide at a particular point known as metacentre, denoted by M. The distance between G and M is known as metacentric height. Equilibrium of a ship is a very important concept regarding its stability. There are generally 3 types of equilibrium condition that a ship may be in.
below the metacentre. GM>0 UNSTABLE EQUILIBRIUM: A ship is said to be in unstable equilibrium if the ship, when subjected to small angles of heel tends to heel further. This condition is true, with reference to negative GM ,i.e, G(centre of gravity) lies above M (metacentre). GM<0 NEUTRAL EQUILIBRIUM: A ship is said to be in neutral equilibrium if the ship, when inclined to small angles of heel tends to remain fixed at that particular angle of heel until and unless another external force is applied. The ship has zero GM i.e KG=KM. GM=0 “GZ” is called the righting lever .It is the perpendicular distance between the centre of gravity(G) and the vertical line passing through the centre of buoyancy. The moment of statical stability acts over this lever GZ. Moment of Statical Stability =(W*GM sinθ. [ GZ=GM sinθ ] GM: It is also known as the geometric metacentric height which defines the calculation of initial static stability of a floating vessel. It is calculated as the distance between the centre of gravity of a ship and its metacentre. A larger metacentric height directly conveys about the greater intact stability against capsizing effect of the ship.
STABLE EQUILIBRIUM: A ship is said to be in stable equilibrium if the ship, when at certain angles of heel tends to return back to its original position. This condition is only possible if the centre of gravity lies
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