Large-eddy simulation of flow over a cylinder with from to : a skin-friction perspective
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AbstractWe present wall-resolved large-eddy simulations (LES) of flow over a smooth-wall circular cylinder up to , where is Reynolds number based on the cylinder diameter and the free-stream speed . The stretched-vortex subgrid-scale (SGS) model is used in the entire simulation domain. For the sub-critical regime, six cases are implemented with . Results are compared with experimental data for both the wall-pressure-coefficient distribution on the cylinder surface, which dominates the drag coefficient, and the skin-friction coefficient, which clearly correlates with the separation behaviour. In the super-critical regime, LES for three values of are carried out at different resolutions. The drag-crisis phenomenon is well captured. For lower resolution, numerical discretization fluctuations are sufficient to stimulate transition, while for higher resolution, an applied boundary-layer perturbation is found to be necessary to stimulate transition. Large-eddy simulation results at , with a mesh of , agree well with the classic experimental measurements of Achenbach (J. Fluid Mech., vol. 34, 1968, pp. 625-639) especially for the skin-friction coefficient, where a spike is produced by the laminar-turbulent transition on the top of a prior separation bubble. We document the properties of the attached-flow boundary layer on the cylinder surface as these vary with . Within the separated portion of the flow, mean-flow separation-reattachment bubbles are observed at some values of , with separation characteristics that are consistent with experimental observations. Time sequences of instantaneous surface portraits of vector skin-friction trajectory fields indicate that the unsteady counterpart of a mean-flow separation-reattachment bubble corresponds to the formation of local flow-reattachment cells, visible as coherent bundles of diverging surface streamlines.
CitationCheng W, Pullin DI, Samtaney R, Zhang W, Gao W (2017) Large-eddy simulation of flow over a cylinder with from to : a skin-friction perspective. Journal of Fluid Mechanics 820: 121–158. Available: http://dx.doi.org/10.1017/jfm.2017.172.
SponsorsW.C. and R.S. were supported by the KAUST Office of Competitive Research Funds (OCRF) under award no. URF/1/1394-01. D.I.P. was partially supported under KAUST OCRF award no. URF/1/1394-01 and partially by NSF award CBET 1235605. The Cray XC40, Shaheen, at KAUST was utilized for all of the reported LES.
PublisherCambridge University Press (CUP)
JournalJournal of Fluid Mechanics