Effects of a pair of adjacent rods on circular cylinder flow

We experimentally investigate the interference effects of a pair of adjacent rods on the aerodynamic characteristics and wake flow patterns of a circular cylinder. The diameter of the rods d = 0.1D, where D is the diameter of the main cylinder. The parameters of the small rods include configuration angles a and gap ratios G/D, where G is the gap distance to the main cylinder. The Reynolds number Re is 32000 within the subcritical range. The flow measurements include surface pressure measurements and particle image velocimetry (PIV) visualizations. Pressure measurement results demonstrate that the rods can change the surface pressure distributions so as to alter the aerodynamic forces acting on the main cylinder. The fluctuating lift coefficient can be reduced by up to 80 % than the baseline case when the rods are placed on the rear side of the cylinder and with a large gap ratio, i.e., a = 150 degrees and G/D = 0.7. The mean drag coefficient can be decreased by up to 57 % when the rods are placed upstream of the cylinder with a relatively small gap ratio (a = 30 degrees and G/D = 0.1). However, such aerodynamic effects become worse with certain rod configu-rations. PIV-visualized flow reveals that the rods can also affect the vortex shedding process, boundary-layer interaction and shear layers. Moreover, the distributions of the time-averaged velocity, streamline, turbulence kinetic energy and Reynolds stresses can also be modified in certain test cases.