水流强度对淹没式方桩局部冲刷特性的影响

为研究不同水流强度作用下淹没式方桩的局部冲刷特性及流场变化,开展了非均匀沙条件下的桩基局部冲刷试验,分析了桩周的冲刷地形、冲刷深度变化规律；利用OpenFOAM对不同水流强度下的桩周流场进行了模拟,讨论了桩前马蹄涡、桩周回流和下降水流的分布特点。结果表明:在清水冲刷条件下,桩周的冲刷坑深度、沙丘高度和受冲刷影响区域大小均随水流强度的增大而增大；在平衡冲刷地形下,高水流强度冲刷后桩周流动更加复杂,冲刷坑内的涡流强度大幅度提高；当水流强度接近1时,粗颗粒泥沙对细颗粒的屏蔽效应会在一定程度上影响桩周最大冲刷深度。

Influence of flow intensity on local scour characteristics of a submerged square pile

To study the local scour characteristics and flow field features of submerged square piles under the effect of different flow intensity, a series of local scour tests were carried out around the pile foundation with the non-uniform sand, and numerical tests were conducted to analyze the scour topography, change law of scour depth and flow turbulence around the square pile. The flow field around the pile were simulated by OpenFOAM. Thereafter, this study discussed the distribution characteristics of horseshoe vortex at the upstream of pile, backflow and downflow around the pile. The results show that the depth of scouring pits, the height of dunes and their sizes around the piles all increase with the increasing of flow intensity under the clear-water scour condition. In the equilibrium scouring terrain, flow around the pile is very complicated, and the turbulence energy in the scour pit becomes larger with the increasing flow intensity value. When the flow intensity is close to 1.0, the shielding effect of coarse-grained sediment on fine particles affects the maximum scour depth of pile perimeter to some extent; thus, the eddy current intensity in the scour pit in front of pile will be enhanced, resulting in more complicated flow behaviour in the scour pit.