A Experimental Study On Lift-off Properties Of Natural Sand-bed Collision

Interaction between sand particle and sand bed is a key issue in the sand saltation research. The lift-off characteristics and splash function of sand particles can help us to understand the interaction between sand particle and sand bed. Most previous experiments took alternative materials with size larger than that of sand particles to take collision experiments between particles and sand bed and obtained many valuable results. To achieve irregular, lift-off characteristics of natural sand particles, we have designed a emitter, which is capable of emitting natural sand particle with adjustable velocity and angle and conducted some experiments to get lift-off characteristics of natural sand particles after the collision between particles and sand bed and finally got a splash function. The main results are as follows:1. Rebounded particles maintained most of the energy after impact, and the speed is in the same order of magnitude with impacted velocity. Rebounded angle of particles is between 0°and 165°and focuses between 10°and 50°, decreasing with the increase of impacted velocity, increasing with the increase of the angle of impact. Rebounded angle is to meet the lognormal distribution. The ratio of the rebounded velocity and impacted velocity of particles varied from 0.02 to 0.78, mainly between 0.1 and 0.6, increasing with the increase of impacted velocity, decreasing with the increase of the angle of impact, which meets the normal distribution. The ratio of the rebounded velocity and impacted velocity of particles in the vertical direction varied from 0 to 1.33, and mainly between 0.05 and 0.45, which is consistent with the situations of rebounded velocity: increasing with the increase of impacted velocity, decreasing with the increase of the angle of impact, the distribution is meets to the normal distribution. The rebounded velocity of the horizontal direction is the same situations with the vertical direction and Co-direction.2. Ejected particles maintained a small part of the energy of impacted particles, and the speed is lower an order of magnitude than impacted velocity. Ejected angle of particles varied from 0°to 180°, concentrated between 10°and 100°,and increasing with the increase of the angle of impact and the velocity of impact. The distribution of ejected angle is meets to the lognormal distribution. The ejected velocity of ejected particles varied from 0m/s to 1.9m/s, mainly between 0.1m/s and 0.6m/s, decreasing with the increase of impacted angle, increasing with the increase of the angle of velocity, which meets the lognormal distribution. The ejected velocity of ejected particles in a vertical direction varied from 0m/s to 1.4m/s, mainly between 0m/s to 0.4m/s, which is consistent with the situations of the ejected velocity: decreasing with the increase of impacted angle, increasing with the increase of the angle of velocity.3. Number of ejected particles(containing the rebounded particle) is from 0 to 17, Where 0 characterizing the impact of particles strike the bed not only did not ejected the bed particles but also did not to rebound and absorbed by bed. Number of ejected particles focused between 1 and 6. Decreasing with the increase of impacted angle, increasing with the increase of the angle of velocity...