Dynamics of vortical structures in cylinder/wall interaction with moderate gap ratio |
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| Institution: | 1. National Energy Technology Laboratories, Department of Energy, Morgantown, WV, USA;2. Department of Mining Engineering and Department of Hydraulics and Environmental Engineering, Pontifical Catholic University of Chile, Santiago, Chile;1. Mechanical Engineering Department, SRM University, NCR Campus, Ghaziabad, Uttar Pradesh - 201204, India;2. Mechanical & Industrial Engineering Department, Indian Institute of Technology Roorkee, Roorkee, Uttarakhand - 247667, India;3. Mechanical Engineering Department, Shri Govindram Seksaria Institute of Technology and Science, Indore, Madhya Pradesh - 452003, India |
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| Abstract: | The interaction between the wake of a transverse circular cylinder and the underlying flat-plate boundary layer with a moderate gap ratio G/D=1.0 is investigated using both hydrogen-bubble-based and PIV-based visualization techniques. The spanwise rollers in the cylinder wake are found to be capable of inducing secondary vortices in the near-wall region. The mutual induction from the counter-clockwise rollers, which are closer to the wall, plays a primary role, so that these secondary vortices present linear lift-up motion at first. Their subsequent evolution dominantly determines the characteristics of the wake/boundary-layer interaction. Two different vortex interaction scenarios are observed: the secondary vortices can be either entrained into the rollers or pushed down towards the wall. This leads to a rapid three-dimensional destabilization process, through which streamwise vortices are generated. And it is suggested that these streamwise vortices are the dominant structures to promote the following boundary layer transition. |
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| Keywords: | Wake/boundary layer interaction Secondary vortex Hydrogen bubble flow visualization PIV measurement |
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