Creep Velocity of Non-Spherical Gravel Particles in Mountainous Regions

Abstract

The movement of sediment particles is governed by the relative magnitude of acting drag and the resistance offered by the particle. The magnitude of drag force that acts on a sediment particle depends on flow parameters as well as on the surface area of the particle exposed to flow. Similarly, the resistance offered by the particle depends on its weight and the surface area of the particle in contact with the stream bed. In the case of spherical particles, orientation does not play an important role, while in the case of non-spherical particles how particle orients itself play a vital role. Therefore, in the case of non-spherical particles, which is the real situation, the movement velocity of sediment particles will depend on their orientation. Numerous studies have been conducted for spherical particles but literature is lacking information for non-spherical particles. In this study, experiments were conducted on coarse solitary non-spherical gravel particles to observe their creep velocity with their changed orientations under varying flow conditions. The experimental finding unveiled that the creep velocity of these particles not only depended on the shape and size of the particles but also on their orientation relative to the flow direction. It was observed that for a particle of a given size, the orientation of the particle which leads to maximum exposed area i.e O2 orientation resulted in the highest creep velocity. The findings of the study have been illustrated with mathematical relationships and graphical representations for various combinations of input variables.