Velocity of Rolling Bed Load Particles

Abstract

AbstractExperimental measurements of the reach-averaged bed-load particle velocity Vp on smooth and rough plane surfaces were analyzed for particles of different shape, size ds, and density G. Particle types included natural quartz particles (1.2 mm<ds<13.6 mm at G=2.65), spherical glass marbles (14.5 mm<ds<29.3 mm at G=2.6), and spherical steel ball bearings (1.6 mm<ds<19 mm at G=8.02). The velocity of 9,739 individual bed load particles continuously rolling on aluminum plates coated with a layer of sand/gravel (roughness 0<ks<3.4 mm) was measured for 356 different conditions. For each flow condition, the reach-averaged particle velocity measurements over a 2 m test reach were repeated at least 15 times to provide mean values and standard deviations. For bed load particles rolling on smooth surfaces (ks=0), it was concluded that (1) Vp is within ±30% of the calculated flow velocity from the vertical velocity profile at the top of the particle; (2) Vp for spheres does not vary much with particle de...