Numerical Simulation of Incipient Motion Parameters of the Sediment Particles with Eulerian-Lagrangian Approach

Solid particles transport in fluid flow is a common phenomenon in nature, and its typical example in hydraulic science is sediment transport in rivers. In a channel with a bed of sedimentary materials, there are no moving particles in the streams with a low discharge and remain steady in their place. As the particle velocity increases, the bed particles begin to move, which is called the threshold of motion of the sediment particles. In this study, using a numerical model based on OpenFOAM software, a two-dimensional simulation of the threshold of group motion of sediment particles in turbulent flow has been investigated. The approach used in the simulation is Eulerian-Lagrangian, in which the continuous phase is emulated in a continuous manner in the form of an Eulerian with finite volume method and sediment particles are simulated in a Lagrangian and particle tracing method. In the current model, the effect of fluid on the particle, the particle on the fluid, and the forces that the particles of the sediment enter to each other are considered. In order to consider the effect of sediment particles inner interacting, a soft contact approach and a friction damper spring impact model were used. The results of the numerical model have been compared with other researchers in the form of critical velocity method and a relation has been proposed for the particle motion threshold criterion. Also, Incipient motion of sediment particles with different criteria has been studied. The results show that the present model can simulate the phenomenon well with proper accuracy.