It was on a proposal of the late Professor Maurice Roy, member of the French Academy of Sciences, that in 1982, the General Assembly of the International Union of Theoretical and Applied Mechanics decided to sponsor a symposium on Turbulent Shear-Layer/Shock-Wave Interactions. This sympo sium might be arranged in Paris -or in its immediate vicinity-during the year 1985. Upon request of Professor Robert Legendre, member of the French Academy of Sciences, the organization of the symposium might be provided by the Office National d'Etudes et de Recherches Aerospatiales (ONERA). The request was very favorably received by Monsieur l'Ingenieur General Andre Auriol, then General Director of ONERA. The subject of interactions between shock-waves and turbulent dissipative layers is of considerable importance for many practical devices and has a wide range of engineering applications. Such phenomena occur almost inevitably in any transonic or supersonic flow and the subject has given rise to an important research effort since the advent of high speed fluid mechanics, more than forty years ago. However, with the coming of age of modern computers and the development of new sophisticated measurement techniques, considerable progress has been made in the field over the past fifteen years. The aim of the symposium was to provide an updated status of the research effort devoted to shear layer/shock-wave interactions and to present the most significant results obtained recently.

An extensive experimental study of three-dimensional shock wave turbulent boundary layer interactions caused by shock generators defined solely by angles has been carried out at Mach 3. Sharp fins, sharp swept fins, swept wedges, and semi-cones have been used to generate a wide range of shock waves. The interaction of these waves with turbulent boundary layers has been investigated by surface flow visualization, mean surface static pressure distributions, flowfield surveys of total pressure and yaw, and several flowfield visualization techniques. Some exploratory high frequency surface pressure measurements have been carried out to evaluate the steadiness of these interactions. Scaling laws for both surface and flowfield features have been derived. Some limited studies were carried out at a Mach number of 2. A flowfield study has shown that the initial part of interactions caused by the same strength and geometrical shock wave generated by different shock generators are all similar. The 'footprints' of the interactions, as shown by surface flow visualization, can be categorized as approximately conical or cylindrical, and the boundaries between these two regions have been defined for both Mach 3 and Mach 2. There are still questions with regards to the detailed flowfield structures and physical mechanisms, but the three-dimensional interactions appeared to be less unsteady than that of two-dimensional separated flows.

Research efforts in shock wave/boundary-layer interactions (SBLI) are motivated by the pursuit of faster, lighter, and more maneuverable aircraft. Flow separation, strong pressure fluctuations, and high aerodynamic heating are all detrimental phenomena associated with these interactions. With a deeper understanding of the physics that drive the inherent unsteady pressure and shear forces, engineers can apply control techniques that target important flow regions and frequencies instead of overdesigning vehicles to survive these adverse effects. However, the mechanisms that drive the unsteady behavior in SBLI have been difficult to isolate and accurate predictions of unsteady pressure are not currently achievable for simulations with realistic Reynolds numbers. In order to further the understanding of 3-D SBLI physics, an experimental investigation of controlled perturbations introduced to a fin-generated swept shock wave/boundary-layer interaction is conducted. The principal mean and unsteady flow features are studied with special emphasis on the difference between separation found in two-dimensional and three-dimensional interactions. Regions of high-amplitude pressure fluctuation on the surface beneath the interaction and coincident unsteady flow features above the surface are identified to support the development of physics-based models of interaction unsteadiness. Several techniques are employed to measure the flow response, including steady and unsteady surface pressure measurements using pressure-sensitive paint (PSP), shadowgraph to capture shock motion, particle image velocimetry (PIV) to quantify velocity fields in the flow, and high-bandwidth unsteady pressure sensors. Global measurement techniques, including steady and unsteady PSP, tomographic PIV, and multiple planes of high-speed stereo PIV permit uniquely illuminating analysis of the flow dynamics. Some of the experimental methods are novel for the facilities and types of flows, and validation and uncertainty quantification efforts are included. Controlled flow perturbations, which have been historically difficult to implement in supersonic flows due to strong momentum of the flow and limited bandwidth of available actuators, are introduced within the interaction to gauge flow response to frequency and location of the disturbance. The perturbations are generated from Resonance-Enhanced Microjets (REM) which produce pulsed supersonic jets at frequencies on the order of several kilohertz. An evolution in the design of surface-mounted, modular REM actuators produces an improved implementation with greater repeatability and bandwidth. The frequency range studied here (between 2 and 4 kHz) has been selected based on separation and reattachment dynamics measured by unsteady pressure on the surface beneath the interaction. Measurements combining the plate and heretofore-unstudied fin surface provide significantly more information about the response of this complex, highly three-dimensional interaction with details that are not easily obtained using traditional sensors. In general, the disturbances created by the actuators were found to excite convective mechanisms within the interactions and remained localized. Large-scale alterations in the flowfield due to microjet blowing are noted, including reduction of the size of separation and smaller shock traverse distances. The flow response to pulsed actuation reveals varying sensitivity of interaction key features, which offers promise for future efforts to design more effective flow control devices.

Separated flows and jets are closely linked in a variety of applications. They are of great importance in various fields of fluid mechanics including vehicle efficiency, technical branches concerned with gas/liquid flows, atmospheric effects on various constructions, etc. Knowledge of the physics of separated flows and jets and the development of reliable control techniques are prerequisite for future progress in the field. These aspects were in focus during the IUTAM-Symposium which was held in Novosibirsk, 9-13 July, 1990. This volume contains a selection of papers presenting recent results of theoretical and numerical studies as well as experimental work on separated flows and jets. The topics include sub- and supersonic, laminar and turbulent separation as well as organized structures in separated flows and jets. The reader will find here the state of the art and major trends for research in this field of aero-hydrodynamics.