3D numerical modelling of scour around a jacket structure with dynamic free surface capturing

Abstract

This paper presents a numerical investigation of local scour with dynamic free surface capturing around a jacket structure. The hydrodynamics and resulting scour are calculated using the open-source CFD model REEF3D. The model solves the Reynolds-averaged Navier–Stokes equations with turbulence closure. The free surface is captured with the level set method. The simulated flow hydrodynamics are coupled with sediment transport algorithms. The modelling of the local scouring process is based on the bed load and the suspended load while accounting for the bed slope for the calculation of the critical bed shear stress. In order to obtain a more realistic prediction of the scour hole, a sand-slide algorithm is implemented to correct the bed slope when it exceeds the angle of repose. The grid and time step size convergence tests are performed to ensure the quality of the simulated hydrodynamics in the numerical wave tank (NWT). The model is validated for local scour around a pile in an experimental flume using different values of Keulegan–Carpenter number (KC). The results show a good agreement with the experimental data. The validated model is applied to simulate scour around a jacket structure. The key findings from the study are the modelling of flow hydrodynamics and the time development of local scour around a jacket exposed to waves and steady current.