Investigation of Wave Breaking Turbulence in Morphodynamic Modelling

Abstract

The effect of wave breaking turbulence on morphodynamics was investigated using Xbeach. To achieve this goal, the results from Xbeach simulation were compared with a large-scale laboratory experiment (CROSSTEX) and a numerical model (COBRAS) which is based on Reynolds-Averaged Navier-Stokes (RANS) equation. To incorporate the impact of wave breaking turbulence, a new near-bed turbulence estimation was suggested in addition to the existing turbulence options in Xbeach. Hydrodynamics results from Xbeach were generally in a good agreement with CROSSTEX and COBRAS. However, morphodynamics from Xbeach did not match well with CROSSTEX nor COBRAS, especially in the vicinity of a longshore bar. Most bathymetric changes occurred in the inner surf zone or swash zone, showing dune erosion. The possible causes of disagreement can be related to the limitation of the depth averaged advection-convection equation used for sediment transport in Xbeach. Also, long wave motions dominates morphologic changes near the dune area. It is concluded that more investigation is still required to better simulate morphodynamics.