FEEDBACK-CONTROL TO DELAY OR ADVANCE LINEAR LOSS OF STABILITY IN PLANAR POISEUILLE FLOW

By using linear stability theory, we demonstrate theoretically that th e critical Reynolds number for the loss of stability of planar Poiseui lle flow can be significantly increased or decreased through the use o f feedback control strategies which enhance or suppress disturbance di ssipating mechanisms in the flow. The controller studied here consists of closely packed, wall mounted, shear stress sensors and thermoelect ric actuators. The sensors detect flow instabilities and direct the ac tuators to alter the fluid's viscosity by modulating the adjacent wall temperature in such a way as to suppress or enhance flow instabilitie s. Results are presented for water and air flows.