DNS of Particle Dispersion and Material Erosion in Gas-Solid Two-Phase Circular Cylinder Wakes

Abstract

Particle dispersion and the resulting material erosion in a three-dimensional wake of circular cylinder were investigated by using direct numerical simulation (DNS). The domain decomposition method with patched grid and the high-order finite difference schemes were used to solve the flow. A new Lagrangian tracking solver was developed to trace the trajectories of particles in the non-uniform and unstructured grid. It is observed that particles at the smaller Stokes numbers can follow the vortex motion and have a relatively uniform distribution in the flow field. They usually collide with the downstream surface of the cylinder. The particles at the larger Stokes numbers tend to maintain their own motion and the particle-cylinder collision occurs in the upstream surface of the cylinder. But particles at the intermediate Stokes number of 1 are observed to assemble in the outer boundaries of the vortex structures and the thin band regions which connect two adjacent eddies. Due to the particular response characteristics, neither can these particles collide with the upstream surface, nor can they collide with the downstream surface of the cylinder. The increase of particle diameter leads to an exponential increase of the collision frequency and the material erosion. The local collision frequency is higher for each kind of particles when the inclination angle approximates zero. But the maximum local erosion happens when the inclination angle is between 30 degree and 60 degree. The larger the particle diameter is, the larger the inclination angle where the maximum erosion happens is. In addition, it is confirmed that the highest erosion ratio occurs when the collision angle between particles and cylinder is around 25 degree for the plastic material.