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Gwenael Hauet
Laboratoire des Ecoulements Céophysiques et Industriels(LEGI), BP 53, 38041 Grenoble Cedex 09, FRANCE

Marcel Lesieur
Equipe MoST / LEGI, B.P. 53, 38041 Grenoble Cedex 09, France


Past experimental and numerical studies have shown that the use of wall-mounted triangular streamwise ribs can lead to drag reduction. This phenomenon was intensively studied during the last twenty years, and DNS of Choi et al. (1993) provided very interesting explanations concerning the role of quasi-longitudinal vortices in the drag-reduction mechanism. This work concerned a flow of constant density above triangular riblets of high height. Large-eddy simulations (LES) have not been used a lot for these studies due to the complex geometry. Here, we employ the immersed boundary techniques proposed by Goldstein et al. (1995). On the upper plane (see Figure 1), an opposite force is imposed to model the riblets. We compare the influence of compressibility upon turbulent intensities of two sawtooth shape riblets. In the last part, we focus on the drag reduction mechanism in the subsonic case.