Impact of body inclination on the flow past a rotating cylinder
Résumé
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⊥) is set to 100. The range of values of the rotation rate (ratio between body surface velocity and U⊥, α∈[0,5.5]) encompasses the two unsteady flow regions and three-dimensional transition identified at normal incidence. The inclination angle (θ) refers to the angle between the current direction and the plane perpendicular to the cylinder axis. A low inclination angle (θ∈{15∘,30∘}), i.e. slight deviation from normal incidence (θ=0∘), has a limited influence on the global evolution of the flow with α, which can be predicted via the independence principle (IP), based on U⊥ only. This highlights the robustness of prior observations made for θ=0∘. Some effects of the axial flow are, however, uncovered in the high-α range; in particular, the single-sided vortex shedding is replaced by an irregular streamwise-oriented structure. In contrast, a large inclination angle (θ=75∘) leads to a major reorganization of flow evolution scenario over the entire α 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.
Domaines
Sciences de l'ingénieur [physics]
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