Numerical simulation on the gas diffusion law due to leakage of submarine pipeline

In order to study the diffusion law of natural gas due to leakage of submarine pipeline in shallow waters and thereby reduce the possibility of major accidents, this paper proposes a consequence prediction and evaluation model for the submarine natural gas pipeline leakage based on the computational fluid dynamics (CFD) theory. The user-defined function (UDF) is used to define the distribution of ocean current velocity, and then combined with VOF model and k-ε turbulence model, the diffusion behavior of leaking natural gas is simulated to identify the influence of different leaking rates, leaking hole diameter and ocean current velocity on the diffusion behavior. The results show that the diffusion of natural gas due to leakage of submarine pipeline usually experiences three forms of changes from gas cloud to big bubbles and then to small bubbles. The larger the leaking rate is, the larger the diameter of gas bubbles is, the smaller the mixing proportion with sea water and the quicker to reach the surface of ocean. The changes of leaking hole diameter have similar influences on the diffusion of natural gas and the leaking rate changes, but the changes of leaking hole diameter have more obvious influences on the diffusion form of natural gas. The larger the ocean current velocity is, the smaller the included angle between the track of gas diffusion and seabed and the larger the diffusion distance alongside the ocean current.