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Article Dans Une Revue Fluids Année : 2019

Optimal Transient Growth in an Incompressible Flow past a Backward-Slanted Step

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With the aim of providing a first step in the quest for a reduction of the aerodynamic drag on the rear-end of a car, we study the phenomena of separation and reattachment of an incompressible flow by focusing on a specific aerodynamic geometry, namely a backward-slanted step at 25 circle of inclination. The ensuing recirculation bubble provides the basis for an analytical and numerical investigation of streamwise-streak generation, lift-up effect, and turbulent-wake and Kelvin-Helmholtz instabilities. A linear stability analysis is performed, and an optimal control problem with a steady volumic forcing is tackled by means of a variational formulation, adjoint methods, penalization schemes, and an orthogonalization algorithm. Dealing with the transient growth of spanwise-periodic perturbations, and inspired by the need of physically-realizable disturbances, we finally provide a procedure attaining a kinetic-energy maximal gain on the order of 106, with respect to the power introduced by the external forcing.
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hal-02176963 , version 1 (25-05-2021)

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Marco Martins Afonso, Philippe Meliga, Eric Serre. Optimal Transient Growth in an Incompressible Flow past a Backward-Slanted Step. Fluids, 2019, 4 (1), pp.33. ⟨10.3390/fluids4010033⟩. ⟨hal-02176963⟩
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