Published online by Cambridge University Press: 02 August 2021
The rotation applied to a circular cylinder, rigidly mounted in a current perpendicular to its axis, can result in the suppression of vortex shedding and of the associated force fluctuations. It also causes the emergence of a myriad of two- and three-dimensional flow regimes. The present paper explores numerically the impact of a deviation from the normal incidence configuration, by considering a rotating cylinder inclined in the current. The Reynolds number based on the body diameter and the magnitude of the current velocity component normal to its axis ($U_\perp$) is set to $100$. The range of values of the rotation rate (ratio between body surface velocity and $U_\perp$, $\alpha \in [0,5.5]$) encompasses the two unsteady flow regions and three-dimensional transition identified at normal incidence. The inclination angle ($\theta$) refers to the angle between the current direction and the plane perpendicular to the cylinder axis. A low inclination angle ($\theta \in \{15^\circ ,30^\circ \}$), i.e. slight deviation from normal incidence ($\theta =0^\circ$), has a limited influence on the global evolution of the flow with $\alpha$, which can be predicted via the independence principle (IP), based on $U_\perp$ only. This highlights the robustness of prior observations made for $\theta =0^\circ$. Some effects of the axial flow are, however, uncovered in the high-$\alpha$ range; in particular, the single-sided vortex shedding is replaced by an irregular streamwise-oriented structure. In contrast, a large inclination angle ($\theta =75^\circ$) leads to a major reorganization of flow evolution scenario over the entire $\alpha$ range, with the disappearance of all steady regimes, the occurrence of structures reflecting the pronounced asymmetry of the configuration (oblique shedding, strongly slanted vorticity tongues) and a dramatic departure of fluid forces from the IP prediction.