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Qing Xu , Fan Zhang
a) 10s after gas release with soil infiltration of 0.1m/d
b) 10s after gas release with soil infiltration of 10m/d
c) 600s after gas release with soil infiltration of 0.1m/d
d) 600s after gas release with soil infiltration of 10m/d
Fig. 6 – Diffusion ranges after 10s and 600s of gas release with soil infiltration of 0.1m/d and 10m/d Tubular diffusion with wind The surface of earth is always exposed to certain environmental conditions such as wind, which has a direct effect on the diffusion of natural gas leakage in air. In this section, the tubular diffusion is simulated with wind at 10 m/s blowing from the left of the calculation area to the right. After 10 seconds of gas release, the natural gas leakage reaches a height of 35m in vertical direction while the maximum upstream and downstream diffusion distance reach to 5m and 10m respectively as a result of wind. After 20 seconds of gas release, the vertical diffusion height of leakage climbs to 45m. After 40 seconds of gas release, the diffusion height
remains at 45m, but the upstream diffusion distance decreases while the downstream one increases rapidly and reaches 25m. Thus the safe region at this moment is the domain where x < 0 m and x > 30 m, y < 30 m and . After 60 seconds of gas release, the leakage continues to go upward to form a new air mass up to 70m high, far below the 120m in the tubular diffusion simulation without wind. However, the downstream diffusion distance is over 70m, which is considerably further than that in the tubular diffusion without wind. After 300 seconds of gas release, the high point of the 5% concentration curve hits 175m in height and the maximum diffusion distance in horizontal direction reaches 200m. After 600 seconds of gas release, the high point
summer / 2013