Numerical Modeling of Bed Profile Evolution Using Large Eddy Simulation

Abstract

Niroshinie, M.A.C., Suzuki, T. and Sasaki, J., 2013. Numerical modeling of bed profile evolution using Large Eddy SimulationIn the surf zone, turbulence and complex fluid motions due to wave breaking cause sediment suspension and movements. For the bed profile, the main causes of topography change are sediment pickup, suspension and settlement. Accurate modeling of the turbulence generated by the flow field is necessary for proper estimation of generated bed profiles. Until now, many types of numerical models, which can estimate bed profile evolution in the surf zone, were developed. Large Eddy Simulation (LES) model was used to estimate the flow fields due to the turbulence generated by wave breaking. The present model consists of a LES model coupled with a sediment pickup/advection model and a bed profile evolution model. The sediment pickup rate is calculated with the sediment pickup function using Shield`s number at the bottom. The sediment particles are 0.15 mm diameter and assumed to be moved with advection of flow field. The continuity equation for sediments is solved to estimate the updating bed. The updated bed is feedback to the hydrodynamics model. Numerical simulation results were compared with the experimental results for velocity vector fields and generated bed profiles. It was observed that, the experimental results of velocity vector fields are consistent with numerical results. Also it was found that, formation of bed profiles near breaking region and swash zone was significant both in numerical and experimental results.