关键词: 海底管道, 气体泄漏, 多相流动, 计算流体力学

Abstract:

To evaluate the consequences of leakage accidents of the shallow subsea natural gas pipeline, this paper builds a calculation model of the shallow subsea pipeline leakage and diffusion process in light of computational fluid dynamics and multiphase flow theories for the strait?crossing section of a natural gas pipeline abroad. Three main factors, leakage aperture, leakage rate, and water flow velocity, are selected as condition variables to simulate the motion process of the gas?liquid two?phase flow under different conditions. The results show that underwater gas diffusion can be divided into three stages: the formation of gas masses above the leakage hole, the mushroom?like rise of gas masses, and the splitting of gas masses from large bubbles into small ones. Leakage aperture and leakage rate have a significant effect on the time when the underwater gas diffuses to the water surface. A larger leakage aperture and a higher leakage rate lead to a larger gas leakage amount, which further results in larger volumes of underwater air masses and ultimately a shorter time for them to reach the water surface. Water flow velocity has a significant effect on gas diffusion trajectory. As water flow velocity increases, the angle between the gas trajectory and the seabed decreases, and the diffusion distance along the ocean current direction becomes longer. This study can provide scientific guidance for emergency treatment of underwater natural gas pipeline leakage accidents.

Key words: Submarine pipeline, Gas leakage, Multiphase flow, Computational fluid dynamics