水下高压气体弹射柱体出筒时尾随气泡的数值模拟

Numerical Simulation of Bubble Formation Dwring Ejection of Cylinder from Tube by High Pressure Gas

从流体动力学角度研究了文题．整个系统分为气泡流场和外部水流场．气泡流场采用零维模型，且假定内部气体作绝热膨胀运动．水流场模型中，假定流体不可压缩、无粘、无旋，忽略液气界面的表面张力，采用在湿表面和气泡表面布置面源的边界无法求解．气泡表面满足运动学边界条件和动力学边界条件，湿表面满足运动学边界条件，据此求解源强的分布．处理了气泡与裙体相碰问题，在气泡与筒体交接处引入虚环，避免了此处强烈的奇性．计算结果显示，裙体所受压力在很短时间内达到最大值，之后迅速下降到负值．

While a cylinder is ejected from a tube underwater, a bubble is formed'by the gas following the cylinder. Focused on the fluid dynamic characteristics , an unsteady, nonlinear process of transient motion of the bubble is investigated in this paper. The whole flow field is divided into the gas flow region in the bubble and the external water flow region. the zerodimensional method is used for the gas flow. We consider the fluid to be incompressible, inviscid and irrotational and that the surface tension is negligible. The boundary element method is applied to solve the problem by distributing the sources on the wet body surface and bubble surface. The velocity potential is determined by satisfying kinematic and dynamic boundary conditions on the bubble surface, and the kinematic boundary conditions on the wet body surface. The connection of the bubble with the skirt-shaped body outside the tube is then successfully handled. The singularity in the joint of the bubble and the tube is avoided by introducing an image plane. Results show that the force on the skirt--shaped body reaches its maximum value transiently, then reduces to a minus value.