Changing lift and drag by jet oscillation: experiments on a circular cylinder with turbulent separation

• Published in: European journal of mechanics, B, Fluids B, Fluids, 2000-09, Vol.19 (5), p.575-595
• Main Authors: Béra, Jean-Christophe, Michard, Marc, Sunyach, Michel, Comte-Bellot, Geneviève
• Format: Article
• Language: English
• Subjects: Actuators; Boundary layers; control; cylinder wake; Cylinders (shapes); Drag; Exact sciences and technology; Flow control; Fluid dynamics; Fundamental areas of phenomenology (including applications); Jets; Lift; Oscillations; Physics; PIV; Pressure distribution; pulsed jet; separation; Turbulent flow; Turbulent flows, convection, and heat transfer; Velocity measurement; Wakes; Wind tunnels
• ISSN: 0997-7546; 1873-7390
• DOI: 10.1016/S0997-7546(00)00122-9

Oscillating jet actuators have been implemented and tested on a circular cylinder. Their action on the separation of turbulent boundary layers is investigated using complementary approaches. Wall pressure distribution shows that a large lift is generated, at the expense, however, of a slightly increased drag. Particle image velocimetry measurements provide the mean and fluctuating velocity fields in the near-wake. The control jet deflects the mean flux lines towards the wall, illustrating that the separation is delayed. This effect appears more and more powerful as the pulsed jet velocity increases. Phase averaging of the PIV fields shows that periodic structures are generated by the control, and how these structures modify the aerodynamic forces by entraining the external flow towards the wall. Finally, a few comparisons are made with laminar boundary layers and some general mechanisms are presented for the lift increase.