Author(s): Chunning Ji; Ante Munjiza; Eldad Avital; John Williams
Linked Author(s): John J.R. Williams
Keywords: Bed load; Saltation; Hydrodynamic forces; Turbulent channel flow; Numerical simulation
Abstract: This paper numerically investigates the particle saltation in a turbulent channel flow having a rough bed consisting of 2-3 layers of densely packed spheres. In this study, we combined three technologies, i. e., the direct numerical simulation of turbulent flow, the combined finite-discrete element modelling of the deformation, movement and collision of the particles, and the immersed boundary method for the fluid-solid interaction problem. Here we present the hydrodynamic forces acting on a particle, together with the particle coordinates and velocities, during a typical saltation. We found the strong correlation between the abrupt decreasing of the particle stream-wise velocity and increasing of the particle vertical velocity at collision which indicates that the continuous saltation of large grain-size particles is controlled by collision parameters such as particle incident angle, local rough bed packing arrangement, particle density, etc. This physics is different from that for large grain-size particle entrainment on which turbulence coherence structures play an important role.
Year: 2013