Numerical study of vortex evolution in compressible flow around a rotating cylinder

This study investigates compressible flow around a rotating circular cylinder at ReD=200 using direct numerical simulation (DNS), with incoming Mach numbers of 0.5, 0.6, and 0.7, and rotation rates ranging from 0 to 7. The analysis focuses on flow behavior, aerodynamic characteristics, and vortex evolution mechanisms. Three distinct flow regimes are identified based on vortex shedding and shock wave presence. Complex shear interactions and localized supersonic zones are observed around the cylinder. In flow regime II, increasing rotation rates reduce vortex strength and shedding frequency, eventually suppressing shedding at higher rates. The shock wave at the cylinder's lower side exhibits non-monotonic strength variations and shifts downstream with increasing rotation rates. The upper vortex is suppressed primarily by the baroclinic effect, while the compressibility effect negatively impacts the lower vortex. Viscous and convective effects contribute positively. At high rotation rates (regime III), vortex suppression results from the balance of baroclinic and viscous effects in the upper vortex and the weakening of viscous and compressibility effects in the lower vortex. Pressure differences between the stagnation point and the low-pressure region beneath the cylinder influence mean lift and drag coefficients. At fixed Mach numbers, the lift coefficient at Ma=0.7 first increases then decreases with rotation rate, while at Ma=0.5 and 0.6, it generally increases. The mean drag coefficient decreases with higher rotation rates. These findings provide insights into shock–vortex interactions and aerodynamic forces in compressible flow, with implications for fluid dynamics and aerospace engineering.