Toward representing wave-induced sediment suspension over sand ripples in RANS models
Toward representing wave-induced sediment suspension over sand ripples in RANS models
复制标题
在 RANS 模型中表示沙波纹上波浪引起的沉积物悬浮
作者：
Amoudry L
近床泥沙过程的参数化通常与海岸泥沙输运模型的预测能力差有关。我们实现了一个二维雷诺平均Navier-Stokes模型，通过再现在大规模波浪水槽实验中获得的测量结果来直接评估这些参数化。泥沙输运模型已耦合到波流体动力学和湍流，和数值实验提供的时间和空间变化的自由表面，流速，泥沙浓度，和湍流量。模型-数据比较能够直接评估关键悬浮过程的表现方式以及泥沙输运模型的固有变异性。我们专注于不同的过程发生以上波纹床与动态平坦的床。数值结果表明，增加粗糙度单独是不够的，有很好的预测能力以上陡峭的波纹。涡卷过程的一些参数化是必要的，一个简单的修改，这将导致恒定的沉积物扩散率以上陡峭的波纹床，足以获得良好的预测波平均悬浮浓度。还提供了湍流动能的模型数据比较，并强调需要考虑涡卷吸对近床湍流和动量传递的影响。
Parameterizations of near‐bed sediment processes are commonly associated with the poor predictive skill of coastal sediment transport models. We implement a two‐dimensional Reynolds‐averaged Navier‐Stokes model to directly assess these parameterizations by reproducing measurements obtained in large‐scale wave flume experiments. A sediment transport model has been coupled to wave hydrodynamics and turbulence, and numerical experiments provide temporal and spatial variations of free surface, flow velocity, sediment concentration, and turbulence quantities. Model‐data comparisons enable the direct assessment of how key suspension processes are represented and of the inherent variability of the sediment transport model. We focus on the different processes occurring above rippled beds versus dynamically flat beds. Numerical results show that increasing roughness alone is not sufficient to have good predictive capability above steep ripples. Some parameterization of the vortex entrainment process is necessary and a simple modification, which leads to constant sediment diffusivity above steep‐rippled beds, is sufficient to obtain good predictions of wave‐averaged suspended concentrations. Model‐data comparisons for the turbulent kinetic energy are also presented and highlight the need to account for the effect of vortex entrainment on near‐bed turbulence and transfer of momentum.