Classifications of flow pattern on three circular cylinders in equilateral-triangular arrangements

Abstract

Classifications of flow pattern on three parallel circular cylinders in equilateral-triangular arrangements in cross uniform flow were investigated by wind tunnel tests. The spacing ratios were in the range of 1.7⩽N/d⩽5.0, where N is the distance between the centers of adjacent cylinders, d the diameter of the cylinders. Both the experiments of pressure distributions on three circular cylinders at Reynolds number 5.5×104 and flow visualizations at Reynolds number 1.4×104 were carried out. It shows that the angles of incident flow strongly influence the flow patterns, and therefore the pressure distributions on any one of the cylinders. Due to the interference of the shear layers and/or wakes, the most complex features of pressure distributions can be found on the cylinder located downstream. As for the different levels of interference regarding the influence of spacing ratio, mainly four different affected regions, i.e., effects of small, transition, medium, and larger spacing can be identified. Within the small spacing ratios, i.e., 1.7⩽N/d⩽2.2, three basic types of interference can be classified. The three basic types are interference of proximity, shear layer reattachment and wake. Furthermore, seven steps of flow pattern can be subdivided as the angles of incident flow vary from 0° to 60°.