Large‐eddy simulation of wave‐breaking induced turbulent coherent structures and suspended sediment transport on a barred beach
Large‐eddy simulation of wave‐breaking induced turbulent coherent structures and suspended sediment transport on a barred beach
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DOI：
10.1002/2016jc011884
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发表时间：
2017
影响因子：
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通讯作者：
Zhe-wei Zhou;T. Hsu;D. Cox;Xiaofeng Liu
中科院分区：
文献类型：
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作者：
Zhe-wei Zhou;T. Hsu;D. Cox;Xiaofeng Liu
为了了解波浪破碎诱导的湍流拟序结构和悬沙输运之间的相互作用，我们报告了一个近原型尺度的禁止海滩波浪破碎过程的大涡模拟（LES）研究。数值模型使用开源CFD工具箱OpenFOAM®实现，其中水和空气相的不可压缩三维过滤Navier-Stokes方程采用有限体积法求解。流体体积（VOF）方法被用来捕捉水-空气界面的演变。利用实测的自由水面高程、湍流平均流速、湍流强度以及首次得到的破碎波湍流度对数值模型进行了验证。模拟结果证实，随着斜降涡（ODEs）接近底部，显着的底部剪切应力产生。值得注意的是，ODE的崩溃到床上也可以引起剧烈的空间和时间变化的动态压力的底部。通过允许沉积物从拦门沙顶部悬浮，间歇性高沉积物悬浮事件及其与高湍流和/或高底部剪切应力事件的相关性进行了研究。模拟的泥沙悬浮率与以前的野外和大型波浪水槽观测结果相似。相干悬浮事件仅占记录的10%，但约占50%的泥沙负荷。模式结果表明，约60 - 70%的相干底部应力事件与表面产生的湍流。几乎所有的相干沙悬浮事件都与相干湍流事件有关，这是由于波浪破碎湍流接近床。本文受版权保护。All rights reserved.
To understand the interaction between wave-breaking induced turbulent coherent structures and suspended sediment transport, we report a Large-Eddy Simulation (LES) study of wave breaking processes over a near-prototype scale barred beach. The numerical model is implemented using the open-source CFD toolbox, OpenFOAM®, in which the incompressible three-dimensional filtered Navier-Stokes equations for the water and air phases are solved with a finite volume scheme. A Volume of Fluid (VOF) method is used to capture the evolution of the water-air interface. The numerical model is validated with measured free surface elevation, turbulence averaged flow velocity, turbulent intensity, and for the first time, the intermittency of breaking wave turbulence. Simulation results confirm that as the obliquely descending eddies (ODEs) approach the bottom, significant bottom shear stress is generated. Remarkably, the collapse of ODEs onto the bed can also cause drastic spatial and temporal changes of dynamic pressure on the bottom. By allowing sediment to be suspended from the bar crest, intermittently high sediment suspension events and their correlation with high turbulence and/or high bottom shear stress events are investigated. The simulated intermittency of sediment suspension is similar to previous field and large wave flume observations. Coherent suspension events account for only 10% of the record but account for about 50% of the sediment load. Model results suggest that about 60∼70% of coherent bottom stress events are associated with surface-generated turbulence. Nearly all the coherent sand suspension events are associated with coherent turbulence events due to wave-breaking turbulence approaching the bed. This article is protected by copyright. All rights reserved.