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Photo by Patrick O'Leary

typically problematic. It’s a cause of noise, vibrations, and material damage. Finding a way to predict precisely when and how cavitation will occur—thereby helping design efficient marine propulsion systems—is the purpose of this project Bhatt’s been working on for the past year, funded by the U.S. Department of Defense’s Multidisciplinary University Research Initiative (MURI). “What we learn here can be applied in many other fields,” he explained. “For instance, in biomedical contexts, we can use ultrasound to form and direct the collapse of these cavitation bubbles to break up kidney stones. And sonoporation—using bubbles to increase the permeability of cell membranes—can be used for directed drug delivery to a particular organ.” The MURI project is led by AEM Professor Krishnan Mahesh, a recipient of the college’s George W. Taylor Award for Distinguished Research and Guillermo E. Borja Award. The University of Minnesota team is collaborating on it with researchers from Caltech, UC Santa Barbara, University of Iowa, University of Michigan, MIT, Johns Hopkins, and the Australian Maritime College. In Minnesota, Bhatt said, their focus is on computational modeling—conducting simulations on supercomputers. Their numerical work fuels and complements the experiments performed by team members at Michigan, Johns Hopkins, and the Australian Maritime College, who

What we learn here can be applied in many other fields. For instance, in biomedical contexts, we can use ultrasound to form and direct the collapse of these cavitation bubbles to break up kidney stones. MRUGANK BHATT

are working on the experimental side, Bhatt said. AEM graduate students Aditya Madabhushi and Filipe Brandão are also part of the study. Madabhushi is exploring cavitation inception in vortex interaction, while Brandão is working on how non-condensable gas can influence bubble formation. Most of what’s known about cavitation, Bhatt said, has only been learned in the past century, starting with the work of British physicist Lord Rayleigh. “The majority of the computational work has been done in the past two or three decades,” he explained, with the advent of supercomputing. “It really speeds up the calculations—you get results much more quickly. “Part of my work is taking the current base code and enabling it to do a higher time step. I’ve worked on something called implicit time marching, which can allow faster calculation of cavitation equations,” Bhatt said. “It’s much easier when you have a single phase in the flow— either just water or just vapor. When you have a mixture of both, interest-

ingly the sound speed drops significantly, which makes the problem more challenging.”

Although the MURI project is just over a year old, Bhatt’s been studying cavitation with Professor Mahesh for nearly four years. He’s enjoying the chance to collaborate with researchers from different universities and different disciplines. “We have people from chemistry working on this, looking at the molecular properties that then can be used for computations at macroscopic level…people from computer science using the latest machine-learning algorithms, people from mathematics, and so on,” he said. They “meet” biweekly via WebEx, with faculty and students from various universities taking turns presenting, and the whole team gathers in person once a year, Bhatt said. “I like that people with expertise in different areas are coming together and sharing their knowledge.”

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Inventing Tomorrow Fall 2018  

In this water-themed issue, students and faculty at the College of Science and Engineering use the latest research techniques to study water...

Inventing Tomorrow Fall 2018  

In this water-themed issue, students and faculty at the College of Science and Engineering use the latest research techniques to study water...