Comparing Flow Past a Rotating Cylinder for Low and High Rotation Rates

Abstract

This study investigates two-dimensional compressible flow past a rotating circular cylinder at a Reynolds number of Re = 3800, focusing on the influence of rotation-induced vortex strength on wake dynamics. Two non-dimensional surface speed ratios, Us * = 5 and 10, are examined to evaluate the effect of actuation intensity on vortex shedding and flow unsteadiness. The governing compressible Navier–Stokes equations are solved using high-fidelity numerical methods. Time-resolved vorticity contours and Fast Fourier Transform (FFT) analysis of signals are used to characterise wake structure and dominant frequency content. Results show that increasing the rotation rate intensifies wake asymmetry and enhances unsteady behaviour. The higher rotation case exhibits stronger and more frequent negative vorticity ejections from the lower surface of the cylinder, leading to amplified lift fluctuations and modified spectral characteristics. Both cases display instability associated with the Magnus–Robins effect, with higher rotation producing greater wake modulation and aerodynamic response.