阶梯溢洪道水力特性及下游冲刷三维数值模拟

Numerical simulation on local scour downstream of a stepped spillway

基于VOF法的RNG k-ε双方程紊流数学模型,对阶梯溢洪道水流压强特性及下游局部冲刷坑的形态和发展进行了三维数值模拟。结果表明:数值模拟结果与试验值吻合良好;台阶面流速沿着台阶凸角的连线形成一个"伪底",流速与坡面近似平行,各个台阶与主流之间存在一个三角形空腔,形成顺时针旋转的漩涡。漩涡中心速度趋近于零,向外逐渐增大,水流表面的流速为最大值。阶梯立面靠近凸角处产生最小压强值,在阶梯水平面从凹角到凸角压强先增大,增大至最大值后又减小。计算了下游冲刷坑的范围及最大冲刷深度,定量给出了冲刷坑最深点流速与冲刷深度的关系。

Based on the RNG k-εtwo equation turbulence model of VOF method,the flow pressure characteristics and the shape and development of local scour pits downstream of a stepped spillway were numerically simulated.The results show that the numerical simulation results are in good agreement with the experimental values.The flow velocity on the step surface forms a"pseudo bottom"along the line of the convex angle of the step,and the flow velocity is approximately parallel to the slope surface.There is a triangle shaped clockwise rotating vortex between each step and the main flow.The velocity in the center of the vortex tends to zero,gradually increases outward,and reaches the maximum velocity on the surface of the free flow.The results show that the minimum pressure value is generated near the convex corner of the ladder facade,and the pressure first increases from the concave angle to the convex corner of the ladder horizontal plane,and then increases to the maximum value and then decreases.The range and maximum scour depth of the downstream scour pit are predicted accurately,and the relationship between the velocity at the deepest point of the scour pit.The scour depth is quantitatively given,which provides technical support for the design and safe operation of water conservancy projects.