Study on release and dispersion behavior of underwater gas based on Eulerian-Lagrangian approach

Key words:  underwater gas  plume  fountain effect  gas pool  Eulerian-Lagrangian approach  computational fluid dynamics (CFD)

Abstract:

Aiming to solve the leakage and diffusion of underwater gases, the diffusion of the gases were simulated based on CFD, by combining the VOF and DPM. Water and air are treated as the continuous phases, while bubbles are treated as the discrete phases. The discrete particles have the same physical properties with bubbles, and the particle density obeys the perfect gas state equation. By virtue of the numerical model, the formation and development process of underwater gas plume, as well as the free surface behavior were studied, and such key parameters as the rise time, gas pool size and fountain height were assessed. The present study indicates that gases spout into water when leakage happens, and the plume volume gradually increases during it approaches the free surface. The underwater gas plume with inverted cone structure is generated when the gas reaches the free surface. The superficial water movement is driven by gas diffusion from water into atmosphere, which forms a circular gas pool and water column on the sea surface. The height of the water column fluctuates after attaining to a peak value, and the radius of the gas pool keeps a stable value after reaching the maximum value. The feasibility of the numerical model is validated by comparing the simulation results with a small scale experiment.