In this paper, a large-eddy simulation study of turbulent free surface flow over a natural rough bed is presented. A three-dimensional multiphase flow model is employed to study the roughness effects on the turbulence properties and free surface dynamics. The governing equations have been discretized using the finite volume method, with the Cartesian cut-cell method being implemented to deal with the precise scanned gravel bed topography and the deformable free surface being captured by a volume of fluid method. The predicted mean flow velocities and turbulence statistics have been compared with experimental data. A close agreement has been obtained between the two sets of results, providing confirmation that this complementary approach to experimental investigations gives further insight into the turbulent free surface flow dynamics over rough beds. It is found that small waves are generated on the free surface due to the roughness effect for the relative low submergence case.

在本文中，介绍了天然粗糙层上湍流自由表面流动的大涡模拟研究。采用三维多相流模型来研究粗糙度对湍流特性和自由表面动力学的影响。控制方程已使用有限体积法离散化，采用笛卡尔切割单元法处理精确扫描的砾石床地形和通过体积流体法捕获的可变形自由表面。预测的平均流速和湍流统计已与实验数据进行了比较。两组结果非常吻合，证实这种对实验研究的补充方法可以进一步了解粗糙床层上的湍流自由表面流动动力学。研究发现，由于相对低淹没情况下的粗糙度效应，在自由表面上会产生小波。