水流强度对推移质三维运动规律的影响

利用粒子示踪技术对恒定均匀明渠流中的推移质颗粒运动进行了测量,采用了三种比重的试验沙,通过改变沙样粒径及水力比降,得到了10组不同水流强度下粒子的三维运动轨迹,计算了粒子三个方向上的速度分量并对大量颗粒的计算结果进行了统计分析。试验结果表明,推移质颗粒运动的平均纵向速度与颗粒雷诺数成幂函数关系,垂向和横向上则基本为随机运动,没有明显的平均运动趋势;颗粒纵向紊动强度及紊动能量均随Shields数增大而增强,由于比重及粒径尺寸的约束,颗粒纵向和垂向紊动强度在数值上大约为清水的一半。

The effect of flow intensity on the bedload 3D movement

The experiments of the bedload 3D movement in steady uniform flow are performed by a particle tracking velocimetry system.The trajectories of coarse particles with 3 types of specific densities and 4 kinds of diameters are recorded in 5 kinds of steady flow with different slopes.Consequently,the 3D velocity components of particles are calculated,and a statistical analysis of large amounts of particles is carried out.The results show that the average longitudinal velocity of bedload versus particle Renolds number conform to the exponential function, while the mean velocities in the vertical and transverse directions are so low that the particles could be considered without significant motion tendency in these two directions.The longitudinal turbulence intensity and turbulence energy become larger with the increase of Shields number.The mean values of longitudinal and vertical turbulence intensities of particles are about half of those in clear water flow because of the restraints of particles' diameter and specific density.