Studying Drag Reduction of Square Cylinder Based on the LBM

In this chapter, the flow around square cylinders with slip boundary placed in a two-dimensional channel is studied with the lattice Boltzmann method. Three modes of single cylinder, oblique cylinder, and side-by-side cylinders are investigated with varied Reynolds numbers from 25 to 200 while relative slip length ranges from 0 to 0.1. The flow state has a great influence on the drag reduction effect of the boundary slip phenomenon. With this study, the application of slip boundary may also lead to additional drag force as the vortex separation is reduced, which is extremely different from simple channel flows. When the drag reduction materials are applied into practice, the flow state must be considered to achieve the desired effect.