【摘要】 针对波浪结构物相互作用的数值模拟问题,本文结合虚拟网格法和梯度增量level set (GALS)法发展了一个基于直角网格的多相流计算方法,其有能力模拟多个动物体与强非线性自由表面的相互作用。该模型采用时间半隐式有限差分法在固定直角网格上求解不可压缩两相流Navier-Stokes方程。采用虚拟网格浸入边界法通过在物体内部布置虚拟网格以考虑浸入边界对流场的影响。GALS方法捕捉强非线性自由表面如波浪翻卷和射流,并通过同时演化level set (LS)方程和其梯度向量方程以提高经典LS方法的精度。基于提出的数值方法,模拟了一系列典型算例,包括交错布置两圆柱相向运动,横向激励下的液舱共振晃荡和圆柱常速入水问题。本文结果与数值和试验结果吻合较好,从不同方面验证了本文计算方法的精度和可靠性。更多还原

【Abstract】 To simulate wave structure interaction, a Cartesian grid based multiphase flow numerical model is presented by combining a ghost cell method and a gradient-augmented level set(GALS)method. This model is capable to simulate multiple moving bodies interacting with highly nonlinear free surface. It involves a semi-implicit finite difference method for the solution of incompressible two-phase Navier-Stokes(N-S) equations on a Cartesian staggered grid. A ghost cell immersed boundary method is used to represent the existence of the moving bodies by placing a set of ghost cells inside the solid. A GALS method is used to capture high non-linear free surface such as overturning wave and jet flow. The classical level set(LS) method is improved by evolving both the LS equation and its gradient vector equation simultaneously. Based on the proposed method, a series of test cases are simulated, including two cylinders moving relative to one another, large amplitude sloshing under horizontal excitation and water entry of a cylinder with a constant speed. The accuracy and reliability of the proposed method are validated in several aspects by comparing presents results with experimental and numerical results.更多还原