A Time‐Domain Boundary Element Method for Wave Diffraction in a Two‐Layer Fluid

Abstract

A time‐domain numerical model is established based on the higher‐order boundary element method (HOBEM) to simulate wave diffraction problem in a two‐layer fluid of finite depth. There are two possible incident wave modes (surface‐wave mode and internal‐wave mode) exist in the incident wave for a prescribed frequency in a two‐layer fluid. For surface‐wave mode, the hydrodynamic characters of fluid particles are similar to single‐layer fluid. For the internal‐wave mode, through the definition of a new function respected to velocity potentials of upper and lower fluid on the interface by using matching condition, a single set of linear equations is set up to compute the time histories of wave forces and wave profiles by using a fourth‐order Runge‐Kutta method. An artificial damping layer is adopted both on the free surface and interface to avoid the wave reflection. Examinations of the accuracy of this time‐domain algorithm are carried out for a truncated cylinder and a rectangular barge, and the results demonstrate the effectiveness of this method.