近边界三维水下爆炸气泡动态特性研究

模拟了近壁、近自由面的水下爆炸气泡的非线性动态特性，假定水下爆炸气泡脉动阶段的流场是无旋、不可压缩的，采用高阶曲面三角形单元离散三维气泡表面，用边界积分法求解气泡的运动，在计算奇异积分时通过重新构造双层位势的主值积分消除双层奇异积分的奇异性，得到更精确的结果，并通过合理的加权方法精确的求解边界面上各节点的真实速度，结合弹性网格技术（elastic mesh technique, EMT）得到优化速度，在整个模拟过程中不需要采用数值光顺。将本文的三维模型与轴对称模型进行的对比分析表明，两种模型计算结果吻合很好，并用三维模型模拟了气泡与自由表面及圆筒的相互作用，水下爆炸气泡在自由表面及圆筒的联合作用下呈现出强非线性。

On dynamics of an underwater explosion bubble near a boundary

The nonlinear dynamics of a gas bubble near the free surface and the cylinder is three-dimensionally computed.The flow field is supposed to be irrotational and incompressible at the underwater explosion impulsive phase.The high-order curved triangular elements are used to disperse the three-dimensional bubble surface.The evolution of the bubble is solved by the boundary integral method,and the singularity of the double layer potential is eliminated by recasting the principal-value integral of the double-layer potential.So the computational result will be more accurate.The real velocity at every node on the boundary surface is solved precisely via the reasonable weighing method,and the elastic mesh technique(EMT)is applied to get the optimum velocity.The mesh-smoothing algorithm is no need during the whole simulating process.Comparisons show that the results by the three-dimensional model are in agreement with those by the axisymmetric model.The present three-dimensional model is used to simulate the interaction between the bubble and the free surface near the cylinder.The behavior of the bubble is strong nonlinear under the combined influence of the free surface and the cylinder.