Numerical Modeling of Surf Zone Hydrodynamics over Movable Bed

Abstract

Understanding of hydrodynamics over moveable bed is crucial for predicting rip current generation. The capability of a numerical model based on Reynolds-averaged Navier-Stokes equations, COBRAS (COrnell BReaking waves And Structures), to simulate hydrodynamics over a movable barred beach was verified. The numerical simulation results were validated with the data collected from a large-scale two-dimensional experiment, which was conducted at the Hinsdale Wave Research Laboratory at Oregon State University. In this study, numerical model results were compared with the experimental results in terms of significant wave heights, wave setup, time-averaged horizontal velocities, and turbulent kinetic energy in different cross-shore locations. The COBRAS model successfully predicted the significant wave heights and setup from the offshore boundary to the vicinity of the bar location, but it slightly overestimated the significant wave heights when broken waves propagated to the shoreline. The numerical simulation was able to predict time-averaged horizontal velocities and turbulent kinetic energy well for all measurement locations. Overestimation of the turbulent kinetic energy at bar trough is because of the limitation of the turbulence closure scheme. Overall, based on the results of this study, the COBRAS model can be used to predict hydrodynamics in barred beaches, but improvement of the turbulence closure scheme is still required.