A model for the simulation of coupled flow-bed form evolution in turbulent flows
A model for the simulation of coupled flow-bed form evolution in turbulent flows
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DOI：
10.1029/2010jc006103
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发表时间：
2010-10
影响因子：
--
通讯作者：
Y. Chou;O. Fringer
中科院分区：
文献类型：
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作者：
Y. Chou;O. Fringer
[1]本文发展了一个三维数值模式来模拟紊流边界层中的床形动力学。在数值模型中，流体动力学在移动的广义边界拟合曲线坐标系中求解，使得域边界精确地遵循复杂的随时间变化的床形几何形状。通过大涡模拟计算的解决湍流特征，而亚网格尺度的湍流运动与动态混合模式。采用二阶精度的任意拉格朗日-欧拉方法保证泥沙质量守恒，而网格随床面运动而任意移动。悬移质的输运采用欧拉方法，并以拾取函数作为床面挟沙的底边界条件。推移质和悬移质的输运结合在床的质量平衡方程中，该方程由于床上方的湍流场和重力（重力引起的雪崩流）引起的时空变化的床应力而演变。床的运动反过来又影响耦合流体动力移动床模拟中的流场，其中床特征由于湍流的解析细节而演变。我们比较了不同的床面高程模型，并通过模拟振荡流中湍流引起的沙涟漪形成和演变来证明本模型的能力。分辨率的研究表明，需要细网格分辨率来解决大量的近壁湍流，这是必不可少的床形启动。
[1] We develop a three-dimensional numerical model to simulate bed form dynamics in a turbulent boundary layer. In the numerical model, hydrodynamics is solved in a moving generalized boundary-fitted curvilinear coordinate system, such that the domain boundary exactly follows complex time-dependent bed form geometry. The resolved turbulent features are computed via large-eddy simulation, while the subgrid scale turbulent motions are modeled with a dynamic mixed model. A second-order accurate arbitrary Lagrangian-Eulerian method is used to guarantee conservation of sediment mass, while the grid moves arbitrarily due to the motion of the bed. Transport of suspended load is modeled using the Eulerian approach with a pickup function as the bottom boundary condition for sediment entrainment at the bed. Transport of bed load and suspended load are combined in a mass balance equation for the bed, which evolves due to the spatiotemporally varying bed stress induced by the turbulent flow field above the bed and gravity (gravity-induced avalanche flow). Motion of the bed in turn affects the flow field in a coupled hydrodynamic moving bed simulation, in which bed features evolve due to resolved details of the turbulent flow. We compare different bed elevation models and demonstrate the capability of the present model through simulation of sand ripple formation and evolution induced by turbulence in an oscillatory flow. A resolution study demonstrates the need for fine grid resolution to resolve a bulk of the near-wall turbulence, which is essential for bed form initiation.