Probability model for gravel sediment entrainment in turbulent flows

• We carry out a direct numerical simulation of turbulent flow.
• We study the drag and lift forces acting on gravel particles.
• A probability model for particle entrainment is proposed.

This paper reports a stochastic model for the prediction of rollover movement probability of gravel particles in turbulent flow. The model is based on the data of a Direct Numerical Simulation of turbulent flow over a rough bed, which is represented by one layer uniform sphere particles. The locations of effective drag and lift forces are explored, as well as the ratio of drag and lift coefficients. The comparison between rollover and pickup probability models indicates that pickup model is valid for cases of critical shear stress less than 0.1 while rollover model works for critical shear stress larger than 0.1. Thus it is reasonable to take into consideration of both of the two models to predict sediment transport behavior in turbulent flows, especially for fluvial rivers which contain different kinds of sediment particles.