Development of feedback control system based on genetic algorithm for wall turbulence

Abstract

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 1mm spanwise spacing are employed for the measurement of streamwise shear stress fluctuations, while arrayed magnetic actuators of 3mm in diameter are used to introduce control input through wall deformation. The frequency response of the sensors and actuators is found to be sufficiently high for the flow conditions presently considered. The wall-normal velocity fluctuations above the actuator is significantly increased, and this indicates that the present actuators can introduce sufficiently large disturbances into the flow field. A preliminary feedback control experiment is also made using a genetic algorithms-based optimal control scheme. Although the number of generations is much smaller than that for convergence, the Reynolds shear stress is decreased for several sets of control parameters among 50 trials.