受漩涡作用的水下块石的起动流速

Critical velocity for initiation motion of rocks under water due to vortex motion

研究绕丁坝水流对坝前河床的冲刷有重要的工程现实意义。在总结以往对冲刷机理研究的基础上,提出漩涡吸附力是引起块石起动的重要因素。通过对流场中竖轴漩涡的分析,简化求解了漩涡对块石的吸附作用力。对块石重新进行受力分析,导出了漩涡作用下新的泥沙起动流速公式。得到的起动流速比经典公式得到的值要小,证明漩涡作用使得块石更容易起动,因而在分析块石受力时不可忽略。结论对探究丁坝坝头冲刷及其他类似的坝头、堤头冲刷稳定计算都有参考价值和启发性。

Water scouring around spur dikes greatly threatens dike stability. Analysis shows that the adsorption affinity of the vortex greatly influences the threshold motion of sediments. A vertical axis vortex was analyzed to study the adsorption affinity of the vortex towards the rocks around a spur dike. The resulting stress on the rocks was used to derive the critical velocity for sediment particles. The critical velocity is lower than that in the classical formula, which indicates that the vortex action more easily initiates rock motion. Therefore, the vortex action should not be neglected when analyzing the critical velocity of rocks. This finding is also applicable to other similar erosion processes such as those around abutments and cofferdam heads.