方柱尾流流态对床面冲淤形态的影响

应用平面二维悬沙数学模型对方柱尾流区的泥沙输运及床面调整进行了数值模拟，并对重要物理参数做了分析说明。数值计算采用时间分裂一全隐式有限差分格式，流场的计算基于沿水深平均的RANS方程。通过系统的数值模拟，揭示了不同来流情况下，方柱尾流区的流态变化，及与之相应的床面变化规律，并对不同流态下的泥沙运动作了分析。计算结果表明在方柱尾流区，不同的流场流态对尾流区的床面调整有明显影响。流场较弱的情况下，尾流区中湍动强度相应较弱，此时悬浮泥沙由于流速减小而普遍落淤，床面应力的减小也致使床面冲刷量减小。随着流场强度的逐渐增大，尾流区中湍动强度相应增强，床面应力增大，同时湍流的强烈交换作用增强了对泥沙的输运作用，床面变化不再是简单的淤积状态，部分区域出现了冲刷。

Effects of Flow Patterns on Changes of Bottom Topography in Wake of Square Cylinder

A horizontal two-dimensional, time-dependent model of hydrodynamic flows and sediment transport is used to predict flows around a square cylinder, suspended sediment transport and bottom deformation in the wake. A model with time-splitting and implicit scheme is adopted to solve the advection-dispersion equation. The depth-averaged RANS equations are employed to compute the hydrodynamic flows based on the hydrostatic assumption, and the transport of sediment in the wake of a square cylinder is simulated and analyzed. The computational results of wake flow and bottom deformation show that the patterns of bottom deformation in the wake dependents on the coherence structure of wake flows. For the incoming flow with lower velocity, the turbulence in the wake is not strong and sediment will deposit due to the decreasing velocity and decreasing friction velocity. However, when the velocity of incoming flow increases, the turbulence becomes stronger and the bottom friction velocity increases, erosion takes place in some zones while deposition dominates in the wake.