A Study On The Drag Coefficient Of Sand Particles In Wind Sand Flux

Drag coefficient is an important parameter for calculating the air resistance in wind sand flux. Since sand particles usually appear in abundance in wind sand flux and the space between each sand particle and the rotation are disposed to disturb the flow field between each sand particles, the previous formula of drag coefficient will undoubtedly cause an error in calculating the drag coefficient. Therefore, in this thesis the present author explores the calculation of drag coefficient in wind sand flux based on numerical simulation of FLUENT.At first, by means of numerical simulation, the present author tries to study the drag coefficient of a single round sand particle and the drag coefficient of two sand particles with different spaces. The numerical simulation result shows that at the surface of the ground, as for the two sand particles placed in front-and back order, the drag coefficient of the front one is less influenced by the space than that of the back one. When the space reaches a certain extent, the drag coefficient of the back one tends to be stable but it is still influenced weakly by the ground surface.Secondly, taking sand concentration and sand shape in the actual situation into account, the drag coefficient of the two sand particles at different heights from the surface and at different wind velocities are calculated by using FLUENT software. Then the space range of drag coefficient influencing the two-dimensional ellipsoidal sand particle is provided and the drag coefficient at different heights in actual wind is also calculated. The result indicates that at a certain wind velocity, as the increase of heights from the surface, the drag coefficient first decreases and then increases and the drag coefficient of sand particles is fitted into a function of heights from the surface. The function is relative to wind velocities. Furthermore, considering that sand particles are rotating in actual wind sand flux, the present author adopts dynamic mesh method, uses FLUENT to make a numerical simulation of the influence of the rotation on drag coefficient of sand particles and then evaluates the influence of rotation of ellipsoidal sand particles on drag coefficient at different angular velocities.On the basis of Chapter Three, this thesis finally carries on a numerical simulation of the drag coefficient of three-dimensional ellipsoidal sand particle and the numerical simulation result is rather similar to that of the two-dimensional ellipsoidal sand particle.