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Cellular vortex shedding in the wake of a tapered plate

Published online by Cambridge University Press:  25 December 2008

VAGESH D. NARASIMHAMURTHY ,
HELGE I. ANDERSSON  and
BJØRNAR PETTERSEN
VAGESH D. NARASIMHAMURTHY*
Affiliation:
Fluids Engineering Division, Department of Energy and Process Engineering, Norwegian University of Science and Technology (NTNU), 7491 Trondheim, [email protected]
HELGE I. ANDERSSON
Affiliation:
Fluids Engineering Division, Department of Energy and Process Engineering, Norwegian University of Science and Technology (NTNU), 7491 Trondheim, [email protected]
BJØRNAR PETTERSEN
Affiliation:
Department of Marine Technology, NTNU, 7491 Trondheim, [email protected]
*
†Email address for correspondence: [email protected]
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Abstract

Direct numerical simulation (DNS) of vortex shedding behind a tapered plate with the taper ratio 20 placed normal to the inflow has been performed. The Reynolds numbers based on the uniform inflow velocity and the width of the plate at the wide and narrow ends were 1000 and 250, respectively. For the first time ever cellular vortex shedding was observed behind a tapered plate in a numerical experiment (DNS). Multiple cells of constant shedding frequency were found along the span of the plate. This is in contrast to apparent lack of cellular vortex shedding found in the high-Reynolds-number experiments by Gaster & Ponsford (Aero. J., vol. 88, 1984, p. 206). However, the present DNS data is in good qualitative agreement with similar high-Reynolds-number experimental data produced by Castro & Watson (Exp. Fluids, vol. 37, 2004, p. 159). It was observed that a tapered plate creates longer formation length coupled with higher base pressure as compared to non-tapered (i.e. uniform) plates. The three-dimensional recirculation bubble was nearly conical in shape. A significant base pressure reduction towards the narrow end of the plate, which results in a corresponding increase in Strouhal number, was noticed. This observation is consistent with the experimental data of Castro & Rogers (Exp. Fluids, vol. 33, 2002, p. 66). Pressure-driven spanwise secondary motion was observed, both in the front stagnation zone and also in the wake, thereby reflecting the three-dimensionality induced by the tapering.

Type
Papers
Information
Journal of Fluid Mechanics , Volume 617 , 25 December 2008 , pp. 355 - 379
Copyright
Copyright © Cambridge University Press 2008

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