Interrelation of structural and kinematic characteristics during free-surface gravity flows of granular materials

Abstract

The interrelationship of flow parameters during free surface gravity flow of cohesionless nonelastic particles is investigated on the basis of a granular medium state equation. The equation establishes the relationship between dilatation, normal pressure and granular temperature. The granular temperature is defined as the sum of three elementary types of kinetic energy of particles in the course of its mutual displacements: relative shear movement, chaotic fluctuation and transversal mass transfer. The investigation was carried out by means of the earlier developed experimental and analytical method presupposing the distribution analysis of particles, falling from the discharge threshold of a rough chute. The profiles of velocity and fraction of the void volume have been determined in rapid gravity flows of modeling materials at simultaneous identification of the interrelationship coefficient of the granular medium state equation. The granular materials consisting of uniform spherical particles differing dominantly in roughness were used as model materials. It was found out the coefficient is equal to 10.3 for a wide range of the chute angle and the flow depth of smooth particles. The analogous coefficient value is observed for rough particles when the high chute angle or small bed depth take place only. However, the coefficient value increases more than four times for rough particles at high values of the bed depth and the chute angle close to the angle of repose of the material. This phenomenon is explained hypothetically by the effect of particle rotation.