河道复杂采砂坑附近流场的数值模拟

Numerical simulation study of flow field around the sandpit with complicate shape in riverbed

数值模拟研究紊流问题的关键是充分考虑雷诺应力的差异,应用各向异性三维代数应力紊流数学模型(ASM)模拟研究了天然河道的次生流问题。以方形管道为算例与试验的比较表明,所应用的ASM模型精度较高;将ASM与非结构网格有机结合模拟分析河道复杂采砂坑,计算成果与前人结果类比,令人满意。ASM模型为研究河床稳定与变形提供了有力工具。分析表明,采砂坑使原稳定的水流形态发生变化,沿主流方向形成纵向涡旋导致采砂坑上游缘口冲刷,坑内的横向次生流则造成横向侵蚀;紊动特性研究表明采砂坑严重影响河床稳定。

The key to study turbulence problems in reality by using numerical simulation is to take into account discrepancy of the Reynolds Stress. A 3-D anisotropic algebraic stress model (ASM) is established successfully to simulate turbulence-driven secondary flow in natural channel. Comparison between the calculated results and experienced results in rectangular ducts has certified the high accuracy of the numerical model. Combining the ASM with unstructured meshes results in more reasonable outcome than ever before for open channels with complicate sandpit. The ASM is a powerful tool to study stability and deformation of riverbeds. The analyzes show that not only the streamwise flow scours the upstream edge of the sandpit but also the secondary current erodes transversal part of the cross section. However, studies in its turbulence characteristic indicate that a sandpit has severe effect on riverbed stability.