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EVALUATION OF GA-BASED FEEDBACK CONTROL SYSTEM FOR DRAG REDUCTION IN WALL TURBULENCE

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

Yuji Suzuki
Department of Mechanical Engineering, The University of Tokyo Hongo, 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 feedback control system for wall turbulence is developed and evaluated in a turbulent channel flow. Arrayed micro hot-film sensors with a spanwise spacing of 1 mm are employed for the measurement of streamwise wall shear stress fluctuations, while arrayed magnetic actuators with 3 mm in spanwise width are used to introduce control input through wall deformation. The frequency response of the sensors and actuators is found to be reasonably high for the flow conditions presently considered. A digital signal processor with a time delay of 1.6 ms is employed to drive output voltage for the actuators. Feedback control experiments are made in a turbulent air channel flow with the aid of a genetic algorithm-based optimal control scheme. It is found that the root-mean-square value of the wall shear stress fluctuations is decreased by up to 9 % among 100 trials in 10 generations. Attempts to develop the micro sensors having higher response are also discussed.