Lattice Boltzmann study of low-Reynolds-number flow past square cylinders with varying slip distributions

Slip distributions have been proved to have significant influence on the flow-past-cylinder problems. However, rare studies focus on the square cylinders. To obtain better understanding of the effect of slip distributions on the flow-past-square-cylinder problems that widely appear in the engineering fields, the flows past a single square cylinder, and two tandem square cylinders under different slip distributions and gap ratios are numerically investigated using the lattice Boltzmann method at low-Reynolds-numbers (25 similar to 200, mainly at 100). The flow structures and drag properties (including the friction drag and the pressure drag) are analyzed. Various slip distributions are found to have minor impacts on the drag reduction of a single cylinder (3.5% in maximum) but larger impacts on that of the tandem cylinders, especially the downstream cylinder (100% in maximum). In addition, flank side slip is found to have important contributions to the drag reduction.