中文摘要：

为了优化泄水建筑物的体型与布置方案,探索流场分布与下游河床局部冲刷间的关联性。结合某大型水电站表、底孔泄洪设施的物理模型实验,基于标准k-ε湍流模型、VOF自由表面捕捉技术,对其联合泄洪3维流场进行数值模拟研究,获得了表孔溢流坝面、底孔及消力池内的流速、水面线、压力等水力特性。通过与水工模型试验结果对比,分析流场结构与下游河道冲刷形态间的关联机制。结果表明：原设计方案消力池内水流波动大,流场紊乱,出池水流2次跌落大且主流下潜河床,横向扩散不充分。相应的物理模型上,下游发生了严重的冲刷,冲刷最严重的右岸岸坡及表孔左导墙下游,恰好是右岸主流贴岸及左岸回流压迫区。通过改进消力池体型,保留底孔与表孔消力池间施工导流墙等措施,显著改善了消力池及出池流态,出池水流2次跌落减小,下潜程度大为减弱,出池主流水平扩散较为充分,横向挤压等得到充分的抑制。相应地,河床冲刷的范围及深度均大为减小,特别是原方案底孔侧对应右岸区域几乎没有发生冲刷。可见,在局部冲刷模拟还很不成熟的情况下,可以采用基于流场分析的办法对下游河床冲刷进行趋势性分析,进而指导泄水建筑物的布置与体型优化。

英文摘要：

In order to optimize the size and layout of discharge structure and explore the relevance between flow field distribution and local scour of the river bed, based on physical experiments in a large-scale hydropower station surface and bottom joint flood discharge facilities and by using standard turbulence model and V0F free surface capture technology, three dimensional flow field of the combined flood was numerically simulated, and the flow velocity,water line and pressure hydraulic characteristics of the surface orifice spillway, bottom outlet and the pond were obtained. By comparing with the experimental results of hydraulic model, the correlation mechanism between the flow field structure and the downstream channel scour pattern was analyzed. Results showed that the original design of the stilling pool water fluctuation, flow disorder, pool water secondary sag and mainstream dive riverbed, lateral diffusion is not sufficient. Serious erosion occurs in the downstream. Through improving the shape of the plunge pool with the methods of retaining the construction diversion wall between low porosity and surface hole stilling pools, the flow regime of stilling basin is significantly improved, the pool water secondary drop decreases, dive is weakened, a pool level of the mainstream diffuses more fully, and lateral extrusion can be suppressed sufficiently. Accordingly, the scope and depth of the riverbed erosion are greatly reduced, especially on the right bank side corresponds to the original proposal prepared hole area almost no erosion occurs.