Flow control: The future

The subject of how control, particularly reactive how control, is broadly introduced, leaving some of the details to other papers in this special volume of the Journal of Aircraft. The ability to manipulate a flowfield actively or passively to effect a desired change is of immense technological importance. In general, methods of control to achieve transition delay, separation postponement, lift enhancement, drag reduction, turbulence augmentation, and noise suppression are sought for both wall-bounded and free-shear flows. An attempt is made to present a unified view of the means by which different methods of control achieve a variety of end results. The important advances in the field of flow control that took place during the past few years are discussed. Spurred br the recent developments in chaos control, microfabrication and neural networks, reactive control of turbulent flows is now in the realm of the possible for future practical devices.