The dynamics and stability of flows around rolling bluff bodies

Abstract : A numerical and experimental study of the flow around rolling and sliding bodies is presented. The geometry of the body is either spherical or cylindrical, and the Reynolds number, based on the diameter and the translation speed of the body, is limited to values lower than 500. The aim of this study is to understand the combined effects of rotation and the presence of a wall on the wake of a bluff body when these two effects are acting simultaneously. In the case of a cylinder travelling along a wall, two- and three-dimensional simulations, as well as a linear stability analysis were carried out. When considering the flow around a sphere rolling or slipping along a wall, both experiments and three-dimensional simulations were utilised. The parameter space considered is defined by the Reynolds number and the non-dimensional rate of rotation of the body. Five values of rotation were considered. These describe motions ranging from "normal"rolling, where there is no slip between the body and the wall, to ‘reversed' rotation, where the body turns in the opposite direction. The numerical scheme uses a spectral element method to simulate the flow in two and three dimensions. Laboratory experiments were carried out in a closed circuit water channel, equipped with a moving floor and boundary layer suction. Dye visualization was then used to identify the different vortical structures present in the wake of the cylinder and sphere.
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Bronwyn Stewart. The dynamics and stability of flows around rolling bluff bodies. Fluid Dynamics [physics.flu-dyn]. Université de Provence - Aix-Marseille I, 2008. English. ⟨tel-00436896⟩

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