Research Article

Experiments in Fluids

, Volume 49, Issue 5, pp 1085-1094

First online:

Drag reduction of a 3D bluff body using coherent streamwise streaks

  • G. PujalsAffiliated withPSA Peugeot Citroën, Centre Technique de VélizyLadHyX, CNRS-École PolytechniqueInstitut Français du Pétrole Email author 
  • , S. DepardonAffiliated withPSA Peugeot Citroën, Centre Technique de Vélizy
  • , C. CossuAffiliated withLadHyX, CNRS-École PolytechniqueIMFT-CNRS, allée du Pr. Camille Soula Email author 

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Separation on the rear-end of an Ahmed body is suppressed by means of large-scale coherent streaks forced on the roof of the model. These streaks originate from an array of suitably shaped cylindrical roughness elements and are amplified by the mean shear through the lift-up effect. Interacting with the mean velocity field at leading order, they induce a strong controlled spanwise modulation. The resulting streaky base flow is observed to sustain the adverse pressure gradient since PIV measurements as well as static wall pressure distributions show that the re-circulation bubble completely vanishes. These modifications of the topology of the flow are associated with a substantial drag reduction, which can be of about 10% when the roughness array is optimally placed on the roof of the bluff body.