A COUPLED FVM-DEM NUMERICAL MODEL FOR SIMULATION OF WATER WAVE INDUCED PORE PRESSURE IN POROUS SEABED

The interaction between water waves and porous seabed is one of the most attractive subjects in the field of coastal engineering. The evaluation of the wave-inducedresponse of a porous seabed is a key factor in the study of sediment transport, because sea beds may be liquefied under the cyclic pressures induced by the incoming waveswhich provides potential nearshore sediment transport. In the last few decades, numerous models for the waveinduced seabed response have been developed with variousassumptions. The examples for these models include [1]: uncoupled models, consolidation models, u–p approximation, dynamic models and poro-elastoplasticmodels. However, The seabed properties change by wave loadings, which in turn affect the wave propagation, a mechanism which has not been considered in theaforementioned models. The coupled FVM-DEM method has been successfully studied for modeling water seepage flow [2]. In this study a coupled FVM-DEM model isintroduced which simulates the wave-porous medium interaction and includes the solution for the fluid and solid parts simultaneously. 2. Methodology A two-dimensional coupled finite volume method (FVM) and discrete element method (DEM) model has been developed to simulate the pore water pressure buildup in the wave-induced seabed. The fluid motion was formulated by Navier-Stokes equations with the consideration of porosity and fluid-particle interaction terms [3]. The solution of the fluid flow is based on a 2DVmodel, (WISE; Width Integrated Stratified Environments) developed by Hejazi et al [4]. WISE uses finite volume method to discretize Reynolds-averaged Navier–Stokesequation on a structured non-orthogonal curvilinear staggered mesh. The model was further developed to include the wave-porous medium interaction usingextended continuity and Navier-Stokes equations. The motion of the individual particles was numerically simulated using the DEM with the inclusion of theinteraction with the fluid. DEM provided a solution of particle-particle collision problem by integration of Newton’s second law equation based on a second orderfinite difference approach.