Velocity of Rolling Bed Load Particles

摘要

Experimental measurements of the reach-averaged bed-load particle velocity V_p on smooth and rough plane surfaces were analyzed for particles of different shape, size d_s, and density G. Particle types included natural quartz particles (1.2 mm 0), for particles of diameter d_s continuously rolling on a stationary bed of roughness k_s, it was concluded that (1) bed load particles roll in continuous motion in the range 2.5 < V_p/u_* < 12.5; (2) steel particles are much slower than spherical marbles (G = 2.6); and (3) the particle velocity increases primarily with a new parameter τ_(*ks) = R_hS_f/(G - 1) k_s in the range 0.008 < τ_(*ks) < 0.2 up to a maximum V_p≈12 u_*. Spherical particles roll slightly faster than natural particles. In a comparison with a large data set that included 1,018 measurements, the analysis of discrepancy ratios showed that the proposed formula was in good agreement with other measurements from the literature.