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GA-BASED FEEDBACK CONTROL SYSTEM FOR DRAG REDUCTION IN TURBULENT CHANNEL FLOW

Yuji Suzuki
Department of Mechanical Engineering, The University of Tokyo Hongo, Bunkyo-ku, Tokyo 113-8656, Japan

Takashi Yoshino
Department of Mechanical Engineering, The University of Tokyo, Hongo, Bunkyo-ku, Tokyo 113-8656, Japan

Tsuyoshi Yamagami
Department of Mechanical Engineering, The University of Tokyo, Hongo 7-3-1, Bunkyo-ku, Tokyo, 113-8656, Japan

Nobuhide Kasagi
Center for Research and Development Strategy, Japan Science and Technology Agency; Department of Mechanical Engineering, The University of Tokyo, Hongo, Bunkyo-ku, Tokyo 113-8656, Japan

Résumé

A prototype system for feedback control of wall turbulence is developed, and its performance is evaluated in a physical experiment. Arrayed micro hot-film sensors with a spanwise spacing of 1 mm are employed for the measurement of the streamwise shear stress fluctuations, while arrayed magnetic actuators having 3 mm in spanwise width are used to introduce control input through wall deformation. A digital signal processor having a time delay of 0.1 ms is employed to drive output voltage for the actuators. Feedback control experiments are made in a turbulent air channel flow. Noise-tolerant genetic algorithm is employed to optimize control parameters. It is found that the wall shear stress is decreased by up to 6 % in physical experiments for the first time. Reynolds shear stress close to the wall is decreased by the present control scheme. By using conditional sampling of DNS database, we found that the present control scheme effectively captures the near-wall shear layer, and introduces wall-normal velocity away from the wall underneath near-wall high-speed regions.