This paper outlines the implementation of an efficient implicit method for a free surface boundary for solving free surface flows with larger time steps. In this method, the governing equations are solved with dynamic conditions applied to the free surface boundary. The position and shape of the free surface are represented with adaptive boundary grid points. Unlike existing explicit methods, the proposed method solves the space conservation equation implicitly, making the calculations more stable and at a lower computational cost. The approach was implemented numerically by developing a new boundary field in OpenFOAM. Several test cases, including propagations of tidal wave, channel surge and solitary wave, were simulated to demonstrate the method’s accuracy. The proposed method accurately predicted the first two cases using larger time steps. The Courant number of the solitary wave case should be less than 1 to reduce numerical errors, which would damp the wave amplitude.

本文概述了一种有效的自由表面边界隐式方法的实现，用于求解具有较大时间步长的自由表面流。在这种方法中，控制方程通过应用于自由表面边界的动态条件来求解。自由表面的位置和形状用自适应边界网格点表示。与现有的显式方法不同，该方法隐式求解空间守恒方程，使计算更稳定，计算成本更低。该方法是通过在 OpenFOAM 中开发一个新的边界场以数值方式实现的。模拟了潮汐波传播、通道浪涌传播和孤立波传播等几个测试案例，证明了该方法的准确性。所提出的方法使用更大的时间步长准确地预测了前两种情况。