Numerical study of the influence of shape and rotation of particles on wind-blown saltation

Hongchao Dun 1 ,2, Ning Huang1 ,2
1Key Laboratory of Mechanics on Disaster and Environment in Western China, Lanzhou, Gansu, China, 2Department of Mechanics, School of Civil Engineering and Mechanics, Lanzhou, Gansu, China

Saltation is a predominant sand particle movement in typical aeolian sand transport. For simplicity, sand particles are considered as perfect spheres and the forces acting on the particle are experienced as concise formulas in almost all of current wind-sand movement models. In fact, most of sand particles in natural environment are non-spherical and usually rotational while they saltate in the air, and the complicated turbulent gas-solid flow caused by irregular shape and rotation of particle cannot be predicted in the models. In this paper, the whole saltation process of single and double elliptical sand rotation movements are simulated with dynamic mesh method and the interaction between air and sand is studied. The results show that the motion feature of rotational non-spherical sand is obviously different from that of spherical one. 1) The trajectory of a rotational elliptical particle is higher and longer than that of spherical one, and the drag and lift forces acting on a rotational elliptical sand particle present a periodicity fluctuation as it rotates in the air; 2) The separating, colliding and tumbling behaviors are observed during their saltation movement for a couple of sand particles. Due to the strong interaction between rotational elliptical double particles and fluid flow, the tumbling frequently occurs and the mid-air collision probability of elliptical sand is lower compared to that of sphere sand. Therefore shape and rotation of sand particles are very important factors affecting wind-sand movement.