Focused wave interaction with a partially-immersed rectangular box using 2-D incompressible SPH on a GPU comparing with experiment and linear theory

Abstract

Wave interaction with bodies spanning the water surface is a common problem. A basic rectangular box of small draft is considered in two dimensions and focused waves are used to minimise reflections. Overtopping occurs in some cases making the inherently mass conservative smoothed particle hydrodynamics (SPH) method appropriate. This is applied in incompressible (divergence-free) form with a 2-D graphics processing unit (GPU) version of the Chow et al. (2019) code with some improvements. A newly parallelised GPU algorithm for the population of a compressed sparse row matrix storage array for the pressure Poisson equation is presented and provides a 327–446 times function speedup and overall simulation time speedups of 1.45–1.78 times with over 5 million particles. The inclusion of the parallel function leads to a completely parallel ISPH algorithm. Peak pressures on the base and front face are compared with experiment and linear (potential-flow) theory. The experiments used periodic focused waves which showed some variation in form about a peak crest although crest elevations were repeatable, and these are reproduced in the model. Converged incompressible SPH (ISPH) values are in approximate agreement with both. Overtopping of the box shows qualitative agreement with experiment. While linear theory cannot account for overtopping or viscous (eddy-shedding) effects, submerged pressure prediction provides a useful approximation. The ISPH model is single phase and limited video evidence suggests that air entrapment can occur in the initial stages of overtopping near the front face. Quite complex vorticity generation and eddy shedding is predicted with free-surface interaction. The study shows the capability and limitations of single phase ISPH for complex wave-body interaction.