SPRINKLER DROPLET EFFECTS ON INFILTRATION .1. IMPACT SIMULATION

The water infiltration rate during sprinkle irrigation is known to decrease due to the impact effects of water droplets on soil-surface structure. In this paper, a numerical simulation model that employs full three-dimensional Navier-Stokes equations and the finite difference procedure is utilized for studying pressure and shear distribution on a soil surface following sprinkler droplet impact. Variables include impact velocity (800 cm/s and 580 cm/s), angle of impact (90-degrees, 60-degrees, and 45-degrees), and surface condition (with and without a water layer). The results indicate that droplets impacting at oblique angles rather than vertically have less impact pressure and less impact force, but a higher shear velocity. For example, the shear velocity, which is a major contributor to soil surface crusting, is approximately 50% higher for a 60-degrees impact than for a vertical impact. The effects of a water layer are to lessen the peak-impact pressure and the shear velocity, but to increase the impact force.