FLOW VISUALIZATION BEHIND THREE CYLINDERS OF EQUAL AND UNEQUAL SPACING

摘要

Turbulent near wakes of three side-by-side circular cylinders with equal or unequal spacing have been experimentally investigated using flow visualization and the hot-wire anemometry. The work aims to understand the effect of unequal cylinder spacing on the vortex streets behind the three cylinders. When the cylinder centre-to-centre spacing is identical, i.e., T_1/d = T_2/d = 1.5, the flow is symmetric about the centreline, with a wide wake behind the central cylinder and two narrow wakes on each side of the wide wake. The dominant frequency in the narrow wakes is about 5.4 times that in the wide wake. However, as T_2/d is slightly increased to 1.6, a remarkable change occurs in terms of the dominant frequencies, vortex formation and downstream evolution. The vortex generation mechanism is also discussed.