Control of flow around a circular cylinder by the use of surface roughness: A computational and experimental approach

Some difficulties are encountered when simulating super-critical Reynolds number (Re) flow over curved surfaces of a building in a low speed boundary layer wind tunnel (BLWT) due to the sensitivity of the flow to Re. Surface roughness on the façade of the cylinder can affect the location of the separation point and the extent of the wake on the leeward face, upon which the wind-induced responses are dependent. This study attempts to control the flow around a circular cylinder through the implementation of artificial surface roughness across the exterior of the cylinder. Subsequently, the size of the artificial roughness will be correlated with Re variations through a computational fluid dynamics wind flow simulations. These correlations will assist in selecting the appropriate artificial roughness that will cause boundary layer transition at points similar to super-critical Re simulations. Several roughness patterns were tested on the circular cylinders, which were subjected to wind flows with varying turbulence intensity. Measurements of the pressure distribution across the façade have been obtained over the Re range of 1x10 to 2x10 in a BLWT. Results from the experiments are compared with previously published experimental data, as well as computational simulations. The results have direct application in the testing of scale models in low speed BLWTs where super-critical flow characteristics are desired.