Journal article
Oscillatory flow regimes for a circular cylinder near a plane boundary
Journal of Fluid Mechanics, Vol.844, pp.127-161
04/04/2018
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Abstract
Oscillatory flow around a circular cylinder close to a plane boundary is numerically investigated at low-to-intermediate Keulegan-Carpenter (KC) and Stokes numbers (beta) for different gap-to-diameter ratios (e/D). A set of unique flow regimes is observed and classified based on the established nomenclature in the (KC, beta)-space. It is found that the flow is not only influenced by e/D but also by the ratio of the thickness of the Stokes boundary layer (delta) to the gap size (e). At relatively large delta/e values, vortex shedding through the gap is suppressed and vortices are only shed from the top of the cylinder. At intermediate values of delta/e, flow through the gap is enhanced, resulting in horizontal gap vortex shedding. As delta/e is further reduced below a critical value, the influence of delta/e becomes negligible and the flow is largely dependent on e/D. A hysteresis phenomenon is observed for the transitions in the flow regime. The physical mechanisms responsible for the hysteresis and the variation of marginal stability curves with e/D are explored at KC = 6 through specifically designed numerical simulations. The Stokes boundary layer over the plane boundary is found to be responsible for the relatively large hysteresis range over 0.25 < e/D < 1.0. Three mechanisms have been identified to the change of the marginal stability curve over e/D, which are the blockage effect due to the geometry setting, the favourable pressure gradient over the gap and the location of the leading eigenmode relative to the cylinder.
Details
- Title
- Oscillatory flow regimes for a circular cylinder near a plane boundary
- Creators
- Chengwang Xiong - University of Western AustraliaLiang Cheng - University of Western AustraliaFeifei Tong - University of Western AustraliaHongwei An - University of Western Australia
- Publication Details
- Journal of Fluid Mechanics, Vol.844, pp.127-161
- Publisher
- Cambridge Univ Press
- Number of pages
- 35
- Grant note
- Australian Government; CGIAR Government of Western Australia University of Western Australia DE150100428 / Australian Research Council through DECRA Scheme; Australian Research Council Pawsey Supercomputing Centre 51479025 / National Natural Science Foundation of China; National Natural Science Foundation of China (NSFC)
- Identifiers
- 991013042413502368
- Academic Unit
- Faculty of Science and Engineering
- Language
- English
- Resource Type
- Journal article