Lattice Boltzmann Simulations of Vortex Ring Impinging on 90 Degrees Edge

We investigate a vortex rings impinging on a 90 degrees edge by using a numerical method. To obtain the flow fields, we use a lattice Boltzmann method with multi relaxation times that is more stable than single relaxation time scheme. From the numerical simulations, the effects on the vortex structures are studied with different distances between the 90 degrees edge and the vortex ring axis. We focus on a fixed Reynolds number of 2100 and an incidence angle of 45 degrees. Our results show that when the ring axis and the edge lie on the same line, the vortex ring is separated into the same two parts. The two vortices induce complicated and vague vortex structures near the walls. On the other hands, secondary vortex rings are formed as the distance increases. Small-scaled vortices are generated around the primary vortices, and then the small vortices play an important role to form the secondary vortex rings. However, the shape of secondary vortex are dependent on where the small vortices are generated. Consequently, the secondary vortex rings show different aspect ratios for the distances.