J. Phys. II France
Volume 6, Numéro 10, October 1996
Page(s) 1343 - 1357
DOI: 10.1051/jp2:1996135
J. Phys. II France 6 (1996) 1343-1357

Global Mode Behavior of the Streamwise Velocity in Wakes

J.E. Wesfreid1, S. Goujon-Durand1, 2 and B.J.A. Zielinska1, 3

1  Physique et Mécanique des Milieux Hétérogènes (PMMH) URA CNRS 857, École Supérieure de Physique et Chimie Industrielles de Paris (ESPCI), 10 rue Vauquelin, 75231 Paris Cedex 05, France
2  Laboratoire d'Électronique, Université Paris XII-Val de Marne, 61 avenue du Général de Gaulle, 94010 Créteil, France
3  Gas Engineering Montrouge/Schlumberger Ind., B.P. 620-05, 92542 Montrouge Cedex, France

(Received 28 November 1995, revised 22 April 1996, accepted 4 July 1996)

We characterize experimentally and numerically the two-dimensional structure of the global mode of the longitudinal component of the velocity in flow behind obstacles of different geometrical shapes. Measurements in a low velocity water tunnel and numerical simulations of the longitudinal component Vx of the oscillating velocity are carried out in the near wake region of the flow where vortex shedding is regular. We find that in the range of Reynolds numbers studied, the position ( $X_{\rm
max}, Y_{\rm max}$ ) of the maximum of the global mode of Vx shift very little away from the central line in the y direction. The amplitude $A_{\rm max}$ of the maximum of the global mode scales as $(R-R_{\rm c})^{1/2}$ in a range of $R-R_{\rm c}$ larger then in previous studies. We also confirm that $X_{\rm max}$ of the global mode scales as $(R-R_{\rm c})^{-1/2}$ in the same range of Reynolds numbers. An analysis of the initial slope of the global mode is presented.

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