Evaluation of turbulence closure models under spilling and plunging breakers in the surf zone

Abstract

Turbulence closure models are evaluated for application to spilling and plunging breakers in the surf zone using open source computational fluid dynamics software. A new library of turbulence models for application to multiphase flows has been developed and is assessed for numerical efficiency and accuracy by comparing against existing laboratory data for surface elevation, velocity and turbulent kinetic energy profiles. Out of the models considered, it was found that, overall, the best model is the nonlinear k − ǫ model. The model is also shown to exhibit different turbulent characteristics between the different breaker types, consistent with experimental data.

Large‐eddy simulation of wave‐breaking induced turbulent coherent structures and suspended sediment transport on a barred beach

“…[2012] and Brown et al [2016], the aspect ratio of Dx and Dz should be close to 1 in order to prevent unreasonable large VOF flux in the x direction, which may lead to artificial steepening of the wave front and Journal of Geophysical Research: Oceans 10.1002/2016JC011884 premature wave breaking. Due to the sloping beach of the wave flume (see Figure 1a), the vertical grid size Dz reduces in the positive x direction.…”

Suspended and Bedload Transport in the Surf Zone: Implications for Sand Transport Models

“…The latter is also required when incorporating TKE effects into reference concentration models. However, an appropriate quantitative description of surf zone TKE is not trivial for present turbulence closure models (Brown et al, 2016). Thirdly, wave breaking leads to large local deformations of the wave shape, which are especially important in terms of bedload-driven bed level changes around the breaker bar.…”

Sand transport processes in the surf and swash zones

“…Although such models have already been proposed (e.g. Steetzel, 1993), it should be noted that it is not trivial to quantify near bed TKE using existing turbulence closure models (Brown et al, 2016). An alternative is a C0 model that is based on breaking wave characteristics such as the relative wave height (Mocke and Smith, 1992) or wave energy dissipation due to breaking (Kobayashi and Johnson, 2001).…”

“…intra wave time scale) and for a range of turbulence models, i.e. k (Lin and Liu, 1998;Brown et al, 2016), k (Brown et al, 2016), or, more advanced, large eddy simulation (Christensen, 2006). Further improvement of turbulence closure models seems essential if near bed TKE is used as input for sediment entrainment or bedload transport.…”

“…Given the poor performance of present turbulence closure models in predicting near bed TKE (Brown et al, 2016), simplified approaches (e.g. Roelvink and Stive, 1989) or empirical predictions for near bed TKE could be considered.…”