Mach Number Effect of Compressible Flow Around a Circular Cylinder

Compressible gas flow past a circular cylinder is numerically studied through CLES approach. The emphasis is put on the influences of freestream (inflow) Mach number on the aerodynamic performances of subsonic and transonic circular cylinders and the flow patterns around the cylinders at subcritical and supercritical Reynolds number regions. Some statistical quantities are calculated and analyzed with respect to freestream (inflow) Mach number. It is found that drag coefficient at different Reynolds number shows a similar trend with small deviations as freestream (inflow) Mach number increases, although these two Reynolds number are of two orders of magnitude difference. However, mean separation angle shows apparent differences. Therefore, it is inferred that the effect of freestream (inflow) Mach number on the drag force prevails over that of Reynolds number in high subsonic and transonic flows. In low Reynolds number flows, the response of mean separation angle to the changes freestream (inflow) Mach number is similar to that of drag coefficient. It is also found that there exists a subcritical Mach number, across which the development of flow fluctuations and the resulting flow patterns show distinct characteristics. It is suggested that subcritical Mach number be between 0.7 and 0.75 for low Reynolds number flows, and fall between 0.65 and 0.7 for high Reynolds number flows.