3D Numerical modelling of pile scour with free surface profile under waves and current using the level set method in model REEF3D

Abstract

Wave action stirs up sediments and keeps it in suspension while currents wash it away from the coastal zone. The combined action of the waves and current close to the sediment bed may worsen the situation by creating excessive sediment transport leading to the failure of hydraulic structures. In this study, numerical modeling of local scour under waves and current is carried out using the open source CFD model REEF3D, which solves the Navier-Stokes equation using the finite difference method. The simulated flow field from the Navier-Stokes equations is coupled with sediment transport algorithms in a numerical waves tank. Further, the calculated bedload and suspended load are linked with the Exner formula to calculate bed elevation changes. The free surface and scoured bed surface are captured using the level set method. Two case scenarios, namely scour under waves and scour under current are run until the equilibrium scour condition is achieved. The simulated results are compared with experimental data of Link (2006) and Sumer & Fredsøe (2001). Good comparison between experimental data and simulated results is observed. It is observed that for equal flow velocity in the flume, sediment transport under current only condition is larger than under waves alone.