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

Mathieu Grandemange (1, 2) , Marc Gohlke (1) , Olivier Cadot (2)

1 Department of Research and Innovation
2 UME - Unité de Mécanique

The sensitivity of the flow around the three-dimensional blunt geometry is investigated experimentally at Reynolds number 9.2 10 4. Vertical and horizontal control cylinders are used to disturb the natural flow which is the superposition of two reflectional symmetry breaking states (Grandemange et al. 2013b). When the perturbation breaks the symmetry of the setup , it can select one of the two asymmetric topologies so that a mean side force is reported. 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 bistable behavior 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 bistable wake is suggested. Finally, a general concept for control strategy of separated flows past three-dimensional bluff bodies can be drawn from these analyses.

Domaines: Mécanique des fluides [physics.class-ph]

Mathieu Grandemange, Marc Gohlke, Olivier Cadot. Turbulent wake past a three-dimensional blunt body. Part 2. Experimental sensitivity analysis. Journal of Fluid Mechanics, 2014, 752, pp.439-461. ⟨hal-01161541⟩