FLOW PAST CIRCULAR-CYLINDER WITH DIFFERENT SURFACE CONFIGURATIONS

Measurements of the mean pressure distributions and Strouhal numbers on partially grooved cylinders with different groove subtend angles were made over a Reynolds number range of 2.0 x 10(4) to 1.3 x 10(5) which was within the subcritical regime of smooth cylinder. The Strouhal number, pressure distributions, and their respective coefficients were found to be a function of the groove subtend angles. In general, a progressive shift of the flow regime to lower Reynolds number was observed with higher subtend angle and a subtend angle of 75 deg was found for optimum drag reduction. With the configuration of asymmetrical groove surface, lower drag, and higher lift coefficients were obtained within the same Reynolds number range. Wake traverse and boundary layer results of the asymmetric grooved cylinder indicated that the flows at the smooth and groove surfaces lied within different flow regimes and a downward shift of the wake.