Hydrodynamic forces acting on a rigid fixed sphere in early transitional regimes |
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| Institution: | 1. Faculty of Civil and Environmental Engineering, Tarbiat Modares University, Tehran, Iran;2. Water Engineering Research Center, Department of Civil Engineering, Tarbiat Modares University, Tehran, Iran;3. Department of Mechanical and Aeronautical Engineering, Clarkson University, Potsdam, NY, USA;1. Conservatoire National des Arts et Métiers, Laboratoire DynFluid, 151, boulevard de l’Hôpital, 75013 Paris, France;2. Univ. Grenoble-Alpes, LJK, 51 rue des Mathématiques, F-38041 Grenoble France;3. EA-7340-M2N-Modélisation, Mathématique et Numérique, Case 2D5000 Conservatoire National des Arts et Métiers, 292 Rue St Martin, 75003 Paris France;1. CIC Virtuhcon, Department for Energy Process Engineering and Chemical Engineering, Technische Universität Bergakademie Freiberg, Fuchsmühlenweg 9, 09596 Freiberg, Germany;2. Department of Chemical and Materials Engineering, University of Alberta, 9107-116 Str., Edmonton, AB T6G 2V4, Canada |
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| Abstract: | A spectral – spectral-element code is used to investigate the hydrodynamic forces acting on a fixed sphere placed in a uniform flow in the Reynolds number interval 10–320] covering the early stages of transition, i.e. the steady axisymmetric regime with detached flow, the steady non-axisymmetric and the unsteady periodic regimes of the sphere wake. The mentioned changes of regimes, shown by several authors to be related to a regular and a Hopf bifurcations in the wake, result in significant changes of hydrodynamic action of the flow on the sphere. In the present paper, we show that the loss of axisymmetry is accompanied not only by an onset of lift but also of a torque and we give accurate values of drag, lift and torque in the whole interval of investigated Reynolds numbers. Among other results show, moreover, that each bifurcation is accompanied also by a change of the trend of the drag versus Reynolds number dependence, the overall qualitative effect of instabilities being an increase of drag. |
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