Fluid Flow Behavior around a Circular Cylinder Perpendicular Arrangement of Circular Cylinders

Fluid flow behavior around a circular cylinder placed downstream of and perpendicular to a single row of cylinders in a uniform flow was investigated varying the distance (L) between upstream and downstream cylinders. Flow visualization techniques (oil-film and smoke-wire methods) and a near-surface flow direction judgement (flow direction probe method) were used, and time-averaged and fluctuating pressure distributions on a circular cylinder were measured under the constant Reynolds number, Re=5×104. It was clarified that the flow structure could be divided as a border of L/D=2.5. In the connection with the vortex transfer, especially, the three-dimensional separation bubble formed at L/D≤2.5 was the result of the stretching of separating shear layers due to the horseshoe-like vortex and inner secondary vortex. At this distance, the span-averaged drag of the downstream cylinder was less than 1.15 times that of a single cylinder.