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Unsteady RANS and detached-eddy simulations of flow around a circular cylinder in ground effect

By T. Nishino, G.T. Roberts and X. Zhang

Abstract

Unsteady Reynolds-averaged Navier–Stokes (URANS) simulations and detached-eddy simulations (DES) were<br/>performed of flow around a circular cylinder placed near and parallel to a moving ground, on which substantially no<br/>boundary layer developed to interfere with the cylinder. The results were compared with experiments previously<br/>reported by the authors to examine how accurately the URANS and DES can predict the cessation of von Ka´rma´ n-type vortex shedding and the attendant critical drag reduction of the cylinder in ground effect. The DES, which were performed in a three-dimensional domain with spanwise periodicity imposed, correctly captured the cessation of the<br/>vortex shedding, whereas both two- and three-dimensional URANS also predicted it but at a much smaller gapto-<br/>diameter ratio compared with the experiments. The wake structures of the cylinder predicted by the DES were in<br/>good agreement with the experiments in both large- and small-gap regimes, and also in the intermediate-gap regime,<br/>where the DES captured the intermittence of the vortex shedding in the near-wake region. Based on the results<br/>obtained, further discussions are also given to the reason why the von Ka´rma´ n-type vortices in the URANS solutions<br/>incorrectly ‘survived’ until the cylinder came much closer to the ground

Topics: TL
Year: 2008
OAI identifier: oai:eprints.soton.ac.uk:64092
Provided by: e-Prints Soton

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