The call for papers for the rUTAM-Symposium on Mechanics of Passive and Active Flow Control brought an overwhelming response of applications for contributions. Fi nally 12 invited lectures, 48 papers and 23 posters were selected by thc Scientific Com mittee to be presented in the conference. 58 papers are published in this volume. Due to the limited number of pages available, poster presentations could not be considered for publication. The editors would like to thank all the members of the Scientific Committee for their very valuable assistance. The papers presented at the rUT AM Symposium were classified under three groups de voted to * Passive Control Methods, * Active Control Methods and * Control Concepts. This was done to contrast at first between the passive techniques where the control power is mainly supplied by the flow itself and the active techniques where the power is pro vided by external sources; the third group was devoted to control concepts for presenting methods of control theory and new techniques of flow control.

This volume contains the Proceedings of the IUTAM Symposium on Mechanics of Passive and Active Flow Control, held at the DLR, GAttingen, in September 1998. This follows an earlier IUTAM Symposium on Turbulence Management and Relaminarisation which was held in Bangalore in 1987. The last decade has witnessed significant advances and research activity in the area of flow control/management, triggered by technological applications as well as scientific curiosity in understanding the structure of complex flows. This volume contains both review and contributed papers in the area of flow control, with emphasis on fluid dynamical mechanisms underlying different passive and active control techniques used in a variety of flows such as bumps, roughnesses, riblets, vortex generators, suction blowing, sound and MEMS; issues such as new control concepts and control strategies are also addressed. The application areas include drag reduction, transition, turbulence and separation, many relevant to aeronautical systems. This volume is very timely and contains a wealth of information on current research in the broad subject of flow control concepts and applications; it should be of particular interest to scientists, engineers and students pursuing research in flow control.