基于欧拉-拉格朗日方法的水下气体泄漏扩散行为研究

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

针对水下气体泄漏扩散问题,基于计算流体动力学(CFD)理论采用流体体积模型(VOF)与离散相模型(DPM)耦合的方法,对气体在水中的扩散过程进行模拟与分析,水和空气作为连续相,泄漏气体作为离散相,离散相粒子与水下气泡具有相同的物理性质,其密度变化服从理想气体状态方程。基于建立的数值模型,研究水下气体羽流的形成和发展过程以及在水面形成的涌流效应,评估气体上浮时间、水面气池尺寸和涌流高度等参数。研究表明:泄漏气体以喷射状涌入水中,上升过程中体积逐渐膨胀增大,运动至水面时形成倒立的锥形羽流结构;气体带动表层水运动,引起羽流两侧表层水回流,在水面产生涌流效应和圆形的气池;涌流高度逐渐增大后呈小幅波动状发展,气池半径逐渐增大后稳定。仿真结果与小尺度实验数据对比验证了数值模型的可行性。

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.