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A simple model for the near wake dynamics of slender bluff bodies in cross-flow is analyzed. It is based on a continuous distribution of van der Pol oscillators arranged along the spanwise extent of the structure and interacting by diffusion. Diffusive interaction is shown to be able to model cellular vortex shedding in shear flow, the cell size being estimated analytically with respect to the model parameters. Moreover, diffusive interaction succeeds in describing qualitatively the global suppression of vortex shedding from a sinuous structure in uniform flow. To cite this article: M.L. Facchinetti et al., C. R. Mecanique 330 (2002) 451-456.  2002 Académie des sciences/Éditions scientifiques et médicales Elsevier SAS fluid mechanics / vortex shedding / 3-D spanwise effects / dynamical systems / van der Pol oscillator Modélisation du détachement tourbillonnaire avec des oscillateurs de van der Pol interagissant par diffusion Résumé Nous analysons un modèle simple de la dynamique du sillage proche derrière une structure élancée. Le modèle est constitué par une distribution continue, le long de la structure, d'oscillateurs de van der Pol interagissant par diffusion. En écoulement cisaillé, la diffusion permet de décrire le détachement tourbillonnaire par cellules, dont la taille est ici calculée analytiquement en fonction des paramètres du modèle. Dans le cas d'une structure sinueuse en écoulement uniforme, le modèle reproduit qualitativement la suppression globale du détachement tourbillonnaire. Pour citer cet article : M.L. Facchinetti et al., C. R. Mecanique 330 (2002) 451-456.  2002 Académie des sciences/Éditions scientifiques et médicales Elsevier SAS mécanique des fluides / détachement tourbillonnaire / effets 3-D / systèmes dynamiques / oscillateur de van der Pol Version française abrégéeOn considère une structure élancée fixe soumise à un écoulement transverse stationnaire [1]. Le phénomène du détachement tourbillonnaire derrière la structure peut présenter d'importants effets tridimensionnels. C'est le cas du détachement tourbillonnaire par cellules, en écoulement cisaillé [2-4] : en présence d'une distribution régulière de la vitesse de l'écoulement amont, le spectre du sillage proche montre une variation par palier, sous forme de cellules caractérisées par une fréquence constante et

Laboratory and numerical experiments have been conducted on the flow of a linearly stratified rotating fluid past isolated obstacles of revolution (conical and cosinesquared profiles). Laboratory experiments are considered for a range of Rossby, Ekman and Burger numbers, the pertinent dynamical parameters of the system. In these experiments, inertial, Coriolis, pressure, viscous and buoyancy forces all play a significant role. Emphasis is given to examining the nature of the time development of the flow fields as well as its long-time behaviour, including eddy shedding. It is shown, for example, that increased stratification tends to diminish the steering effect of the obstacle, other parameters being fixed, at elevation levels above the topography. At levels below the top of the obstacle, increased stratification tends to force the fluid around rather than over the body and this, in turn, tends to develop vortex shedding at smaller Reynolds numbers than would occur in corresponding lower stratification cases. Data for the cone reveal that the Strouhal number for the eddy-shedding regime is relatively insensitive to the values of Ro , Ek and S for the range of parameters investigated. Stratification tends to induce lee waves in the topography wake, and the nature of this lee-wave pattern is modified by the presence of rotation. For example, it is demonstrated that for vertically upward rotation, the lee waves on the right, facing downstream, have a larger amplitude than their counterparts at the same location on the left. The steering effects, as predicted by a three-level quasigeostrophic numerical model, are shown to be in good agreement with the laboratory results for a narrow range of parameter space. The numerical model is used to examine the effects of rotation, friction and stratification in modifying the flow. The quasigeostrophic numerical simulations do not produce eddy shedding, and it is concluded that a full, primitive equation numerical model would be needed to explore this phenomenon.