Discrete particle model of aeolian sand transport: Comparison of 2D and 2.5D simulations

A discrete particle model is applied to describe aeolian sand transport. In this model, the inter-particle collisions and the fluid–particle coupling interactions are considered, the fluid turbulence is treated with a mixing length theory, and the motion of each particle is directly tracked. The 2.5D model includes the 2D flow for gas and the 3D motion for sand particles. The differences between 2D and 2.5D simulations are compared. The results show that the 2.5D simulation can produce the non-uniform distribution of particle in the spanwise direction. In the 2D simulation, the particle motion is limited only to a vertical plane, so the number density or concentration of particle in the 2D simulation is artificially increased. The particle concentration in the 2.5D simulation is less than that in the 2D simulation. Both the mean horizontal velocity of particles and the wind velocity in the 2.5D simulation are more than those obtained in the 2D simulation. The decay rate of sand mass flux with increasing height in the 2.5D simulation is larger than that in the 2D simulation. In the saltation layer, the particle shear stress in the 2.5D simulation is less than that in the 2D simulation, while the fluid shear stress in the 2.5D simulation is larger than that in the 2D simulation. The 2.5D model can consider the particle motion in all the three coordinate directions and improve the simulated results of the 2D model, and thus acquire better results.