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基于颗粒间相对暴露度的分布规律,确定了河床近底水流流速有效作用点高度yb和近底时均流速。在此基础上,分别比较了滚动模式、滑动模式和跃移模式下泥沙临界起动平衡条件,推导出了三种起动模式下的起动概率。经分析发现:在床面泥沙颗粒处于相对暴露度均值为0.16状态下及同样的水流条件下,泥沙滑动模式和滚动模式起动概率处于同一量级,滑动模式更容易起动,跃移模式最难起动;当水流强度较小时,泥沙颗粒以滚动(间或滑动)模式起动为主,反之,以跃移模式起动为主。
Based on the distribution law of the relative exposure between particles, the effective action point height (Yb) of near-bottom water flow velocity in the river bed and the mean velocity at near bottom are determined. On this basis, the critical starting conditions of sediment under rolling mode, sliding mode and jumping mode are compared respectively, and the starting probability under three starting modes is deduced. The results show that under the condition of mean relative exposure of bed sediment particles of 0.16 and under the same water flow conditions, the slip rates of sediment are the same order as those of rolling mode, and the slip mode is easier to start. Difficult to start; when the intensity of the water flow is small, the sediment particles start with the rolling (inter-or sliding) mode, otherwise, the main mode is the jump mode.