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Opposition Control of Near-wall Turbulence - A Real-time Experiment

Henry Rebbeck
Flexifoil International 27 Regal Drive, Soham, Cambridge CS7 5SE, UK

Kwing-So Choi
School of Mechanical, Materials, Manufacturing Engineering and Management, University of Nottingham, University Park, Nottingham NG7 2RD, UK

Resumo

Recent DNS studies have shown that the near-wall turbulence can be controlled with a simple control scheme, providing up to 25% skin-friction drag reduction. Opposition control establishes a 'virtual wall', a plane with effectively no through flow, preventing a downwash of high-momentum fluid towards the wall during the sweep events. In this paper, we report recent experimental results where opposition control was carried out in real time using wall-normal jet from an actuator. By improving on the detection technique and the actuator used, we were able to selectively cancel the downwash of high-momentum fluid in the near-wall region of the turbulent boundary layer.