Numerical Study of Continuous Saltation

Continuous saltation is understood to occur when a particle in a horizontally flowing fluid rebounds repeatedly from the bed of a flume without being deposited. The motion of an isolated spherical particle near a bed of similar particles in an orderly horizontal array was simulated numerically. A three-dimensional model based on coefficients of restitution and friction is developed for the bed interaction with the moving particle. It is shown that the upward component of the drag force on a downward moving particle can be greater than the net gravitational force on that particle. For different values of the relative particle density, the results for average height of bounce, average particle horizontal velocity, and rate of solids transport cannot be reduced to a single well-ordered family of curves when the Shields entrainment function and the particle Reynolds number are used as independent parameters. The results can be correlated if these parameters are each multiplied by a factor containing the relative particle density.