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Turbulent wake past a three-dimensional blunt body. Part 2. Experimental sensitivity analysis

Published online by Cambridge University Press:  07 July 2014

M. Grandemange ,
M. Gohlke  and
O. Cadot
M. Grandemange
Affiliation:
Unité de Mécanique, Ecole Nationale Supérieure de Techniques Avancées, ParisTech, 828 Boulevard des Maréchaux, 91762 Palaiseau CEDEX, France PSA Peugeot Citroën, Centre Technique de Vélizy, Route de Gisy, 78943 Vélizy-Villacoublay CEDEX, France
M. Gohlke
Affiliation:
PSA Peugeot Citroën, Centre Technique de Vélizy, Route de Gisy, 78943 Vélizy-Villacoublay CEDEX, France
O. Cadot*
Affiliation:
Unité de Mécanique, Ecole Nationale Supérieure de Techniques Avancées, ParisTech, 828 Boulevard des Maréchaux, 91762 Palaiseau CEDEX, France
*
†Email address for correspondence: cadot@ensta.fr
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Abstract

The sensitivity of the flow around three-dimensional blunt geometry is investigated experimentally at Reynolds number $\def \xmlpi #1{}\def \mathsfbi #1{\boldsymbol {\mathsf {#1}}}\let \le =\leqslant \let \leq =\leqslant \let \ge =\geqslant \let \geq =\geqslant \def \Pr {\mathit {Pr}}\def \Fr {\mathit {Fr}}\def \Rey {\mathit {Re}}9.2\times 10^4$. Vertical and horizontal control cylinders are used to disturb the natural flow which is the superposition of two reflectional symmetry breaking states (see Part 1 of this study, Grandemange, Gohlke & Cadot, J. Fluid Mech., vol. 722, 2013b, pp. 51–84). When the perturbation breaks the symmetry of the set-up, it can select one of the two asymmetric topologies so that a mean side force is found. When the reflectional symmetry is preserved, some positions of horizontal and vertical control cylinders alter the natural bi-stability of the flow which may result in drag reduction. In addition, it is found that the horizontal perturbation affects the lift force especially when the top and bottom mixing layers are disturbed. The ability of the disturbances to suppress the bi-stable behaviour is discussed and, introducing a formalism of induced drag, a quantification of the impact on the drag of the cross-flow forces observed for the natural bi-stable wake is suggested. Finally, a general concept for a control strategy of separated flows past three-dimensional bluff bodies can be drawn up from these analyses.

JFM classification

Aerodynamics: Aerodynamics Wakes/Jets: Separated flows Wakes/Jets: Wakes/Jets
Type
Papers
Information
Journal of Fluid Mechanics , Volume 752 , 10 August 2014 , pp. 439 - 461
Copyright
© 2014 Cambridge University Press 

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