The effect of the length of dike and protrusion ratio of river on the incipient velocity is analyzed, it sets up the foundation of evaluating the influence of vertical vortex on the local scour.

• 分析了坝长和束窄率对瞬时起动流速的影响，为进一步分析竖轴旋涡对坝前颗粒运动及局部冲刷的作用建立了基础。