High-speed water impacts of flat plates solved by a SPH-FV Coupled approach

Recently, an algorithm for coupling a Finite Volume (FV) method, that discretize the Navier-Stokes equations on block structured Eulerian grids, with the weakly-compressible SPH has been presented in Chiron et al. (2018). This coupling strategy takes advantage of the SPH method to discretize flow regions close to highly-deforming free-surfaces and a Finite Volume method to resolve the bulk flow and regions where grid stretching can be favourably used. The information exchange between the two numerical schemes is established through overlapping zones. In the present work such a coupling paradigm is extended to the 3D framework for the simulation of the violent water entry of flat plates with both horizontal and vertical velocity components. As described in the theoretical work by Zhao and Faltinsen (1993), for small deadrise angles a very thin, high-speed jet of water is formed, and the time-spatial gradients of the pressure field are extremely high. The coupling strategy in this case can be extremely powerful: the impact region can be resolved by SPH, which can effectively describe the local complex free surface evolution, whereas the FV can solve the remaining part of the domain by the adoption of stretched grids (see figure). The results are compared to ditching experiments recently carried out at CNR-INM.