Experimental investigations of prismatic cylinders in flow with harmonic pulsations

The effect of small amplitude harmonic flow pulsations on the wake development behind prismatic cylinders were examined by making mean and fluctuating pressure measurements in a wind tunnel and by employing hydrogen bubble flow visualization in a water channel. Configurations with slenderness ratios (streamwise body dimension/transverse body dimension) of 0.5 and 2.0, were used. For the 0.5 body and with pulsation amplitudes of the order of 1% of free stream velocity, the mean base pressure decreases by up to 20% compared with its value in steady flow. For the 2.0 body the perturbations have no significant effect of the mean base pressure. For the 0.5 body, the decrease in base pressure with forcing at 4 times the natural shedding frequency disappears for all 3D cases, while the magnitude of the decrease for forcing at twice the natural shedding frequency depends on aspect ratio.