推移质颗粒平均运动特性的试验研究

Experimental study on average movement characteristics of bed-load particles

采用三维粒子示踪测速技术,通过分别变化示踪粒子的粒径、比重以及水力比降等条件,观测了10种不同水沙条件下推移质颗粒的三维运动,对推移质颗粒的平均运动规律进行了统计分析。研究结果表明,推移质颗粒的纵向速度既不是Einstein假定的11.6u*,也不是Bagnold假定的比清水流速小一个ω值。在分析坡降、粒径和比重对推移质平均纵向速度影响的基础上,根据Bagnold和Einstein两种表述方法以及实测资料分别得出推移质纵向平均速度的两个表达式。

The three dimensional movements of bed-load particles in open channel with different grain diameters and different specific gravities under the conditions of different hydraulic gradient are measured by means of PTV（Particle Tracking Veloeimentry）technique. The average movement characteristics of the particles are analyzed by statistics. The results show that the longitudinal average velocities of the particles neither agree with the law suggested by Einstein, nor obey the law assumed by Bagnold. The Einstein＇ s law is that the particle velocity is equal to 11.6 times of shear velocity and the Bagnold＇ s law assumes the velocity equal to the difference between flow velocity at corresponding water depth and settling velocity of particle. Two formulas for determining the velocity of particle in the forms of expression given by Einstein and Bagnold are obtained according to the statistical results of experimental data respectively.