Effect of Rotation on the Three-Dimensional Flow around Two Side-by-Side Circular Cylinders at Reynolds Number 3900

Flow around two side-by-side circular cylinders is investigated by implicit large eddy simulation (ILES) at the spacing ratio T/D=2.0 and Reynolds number Re=3900. First, the results of the stationary case show that the flow of two stationary side-by-side circular cylinders is characterized by the biased flow pattern and the flip-flopping phenomenon. The generation mechanism is attributed to the relative development degree between two gap-side shear layers and the merging tendency between the gap-side shear layer of one cylinder and the outside vortices from the other cylinder, which generates a strong pulling effect acting on the gap-side shear layer to pull it toward one side and deflects the gap flow. Then, two rotation control methods, namely forward rotation and backward rotation, are introduced to control the biased flow pattern and the flip-flopping phenomenon. The numerical results show that the control mechanisms are different. The forward rotation enlarges the distance between the shear layers, so the merging process can hardly occur and the gap flow is not biased. The backward rotation shortens the shear layer lengths and the distance between them, contributing to a weak interaction which can hardly pull the shear layer toward one side.