Abstract:

A three-dimensional CFD numerical model for the leakage of underwater gas pipelines is established. The variation of bubble plume velocity, plume radius and fountain height at different leakage rates and water depths are studied. The results show that the bubble plume has experienced the initial stage, the full development stage and the surface flow stage, accompanied by the phenomenon of entrainment and turbulent boiling. The plume radial velocity is approximately Gaussian distribution and decreases with the radial distance. The axial velocity of plume decreases with the increase of water depth, and the velocity of plume decreases rapidly at the position near the leakage hole. With the development of bubble plume turbulence, plume radius gradually develops to both sides and increases linearly with water depth. Compared with the integral model, although the CFD model is more complicated in calculation, but the predicted results are roughly consistent with the experiment, it is necessary to carry out experiments with high leakage flow rate under deep water conditions to determine the accurate empirical coefficient to further improve the calculation accuracy of the integral model.

Key words: underwater pipelines, leakage, multiphase flow, bubble plume, diffusion, numerical simulation

摘要：

建立了水下输气管道泄漏三维CFD数值模型，同时基于积分模型建立了预测数学模型，研究了不同泄漏速率和水深下气体在水体中扩散的速度、羽流半径以及上升到水面时形成泉涌高度的变化规律，并利用实验验证了两种模型的准确性，两种模型可以准确地模拟羽流特征参数的变化。结果表明：水下天然气管道泄漏扩散经历了初始阶段、充分发展阶段和表面流动阶段三个阶段，在气泡羽流上升过程中伴随着卷吸和紊动沸腾现象；羽流的径向速度近似呈高斯分布并且随着径向距离的增加逐渐降低；羽流的轴向速度随着水深的增加而降低，且在接近泄漏孔口的位置，轴线上羽流的速度急速衰减；随着气泡羽流紊动的发展，羽流半径逐渐向两侧发展并且随着水深近似呈线性增长。

关键词: 输气管道, 泄漏, 多相流, 气泡羽流, 扩散, 数值模拟