A numerical study of bore runup a slope

The runup process of a fully developed turbulent bore propagating over a uniform slope is studied numerically using a 2-D Reynolds Averaged Navier-Stokes (RANS) solver, coupled with a Volume of Fluid (VOF) method and a non-linear k - S turbulence closure. Numerical results for the assemble-averaged flow field show much better agreement with existing experimental data than those obtained from theoretical and numerical results based on shallow water equations (SWE). The numerical simulations are also able to illustrate the processes of bore collapse and other small scale features, such as the ‘mini-breaking’. Numerical results of the turbulence field demonstrate that the maximum turbulent kinetic energy (TKE) intensity occurs near the still water shoreline where the bore collapses. The subsequent decay of TKE reveals two distinct stages in terms of the decay rate. In the region near the still water shoreline, the dominant process is the advection of the strong TKE intensity produced by bore collapse; in the region landwards from the shoreline, the turbulence field has forgotten the influence of bore collapse and the TKE decay rate is very close to that of homogenous grid turbulence.