TURBULENCE SUPPRESSION BY ACTIVE CONTROL

It has recently been recognized that the non-normality of the dynamica l operator obtained by the linearization of the equations of motion ab out the strongly sheared background flow plays a central role in the d ynamics of both fully developed turbulence and laminar/turbulent trans ition. This advance has led to the development of a deterministic theo ry for the role of coherent structures in shear turbulence as well as a stochastic theory for the maintenance of the turbulent state. In thi s work the theory of stochastically forced non-normal dynamical system s is extended to explore the possibility of controlling the transition process and of suppressing fully developed shear turbulence. Modeling turbulence as a stochastically forced non-normal dynamical system all ows a great variety of control strategies to be explored and their phy sical mechanism understood. Two distinct active control mechanisms hav e been found to produce suppression of turbulent energy by up to 70%. A physical explanation of these effective control mechanisms is given and possible applications are discussed. (C) 1996 American Institute o f Physics.