Vortex dynamics of a cylinder wake in proximity to a wall |
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| Authors: | S. Sarkar Sudipto Sarkar |
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| Affiliation: | 1. State Key Laboratory of Hydraulic Engineering Simulation and Safety, Tianjin University, Tianjin 300072, China;2. School of Civil, Environmental and Mining Engineering, The University of Western Australia, Crawley, WA 6009, Australia;1. Maritime Research Centre, Nanyang Technological University, Singapore 639798, Singapore;2. College of Logistics Engineering, Shanghai Maritime University, Shanghai 201306, China;3. Nanyang Environment and Water Research Institute, School of Civil and Environmental Engineering, Nanyang Technological University, Singapore 639798, Singapore;1. School of Civil and Environmental Engineering, Nanyang Technological University, Singapore;2. Centre for Offshore Research and Engineering, Department of Civil and Environmental Engineering, National University of Singapore, 1 Engineering Drive 2, Singapore 117576, Singapore |
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| Abstract: | Large-eddy simulations (LES) are used to investigate the modifications of wake dynamics and turbulence characteristics behind a circular cylinder placed near a wall for varying gap-to-diameter (G/D) ratios (where G signifies the gap between the wall and the cylinder, and D the cylinder diameter). The three-dimensional (3-D), time-dependent, incompressible Navier–Stokes equations with a dynamic subgrid-scale model are solved using a symmetry-preserving finite-difference scheme of second-order spatial and temporal accuracy. The immersed boundary (IB) method is employed to impose the no-slip boundary condition on the cylinder surface. Flow visualizations along with turbulence statistics are presented to gain insight into the flow structures that are due to interaction between the shear layers and the approaching boundary layer. Apart from the vortex shedding mechanism, the paper illustrates the physics involving the shear layer transition, stretching, breakdown and turbulence generation, either qualitatively or quantitatively, in the presence of a wall for a Reynolds number of Re=1440 (based on D and the inlet free-stream velocity U∞). |
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