Understanding And Predicting Shockwave And Turbulent Boundary Layer Interactions

Shockwave and turbulent boundary layer interactions produce intense localized pressure loads and heating rates that can have a dramatic influence on the drag and heating experienced by a high-speed vehicle, and can significantly impact fuel mixing and combustion in propulsion systems. The lack of standardized and traceable databases prevents the calibration of computational fluid dynamic models to accurately represent these critical flow phenomena. In this work we accomplished the development and validation against experiments at the same flow and boundary conditions of direct numerical simulations of shock and turbulent boundary layer interactions. We pioneered the development of a unique numerical capability that allows the accurate and detailed three-dimensional turbulence data at a reasonable turn-around time. In turn, parametric studies of fundamental flow physics are feasible, for the first time. By accurate, it is meant that the numerical uncertainty is within the experimental error.

Shock wave-boundary-layer interaction (SBLI) is a fundamental phenomenon in gas dynamics that is observed in many practical situations, ranging from transonic aircraft wings to hypersonic vehicles and engines. SBLIs have the potential to pose serious problems in a flowfield; hence they often prove to be a critical - or even design limiting - issue for many aerospace applications. This is the first book devoted solely to a comprehensive, state-of-the-art explanation of this phenomenon. It includes a description of the basic fluid mechanics of SBLIs plus contributions from leading international experts who share their insight into their physics and the impact they have in practical flow situations. This book is for practitioners and graduate students in aerodynamics who wish to familiarize themselves with all aspects of SBLI flows. It is a valuable resource for specialists because it compiles experimental, computational and theoretical knowledge in one place.

Laminar and turbulent boundary layer interactions with externally generated shock waves.

"Shock-wave/boundary-layer interactions continue to be ubiquitous phenomena in supersonic and hypersonic aerodynamics, and their importance is often critical as, for example, for hypersonic controls and for air intakes in general. This is the reason for the continuous research efforts in this field, aiming at developing reliable methodologies for future vehicle design. Results from these programmes have been reported. The present course reviews the recent progress in this field. In particular, a large part of the course is devoted to swept interactions, both laminar and turbulent, including a discussion of the following topics: (1) The flowfield structure; (2) The scaling and similarity laws; (3) The effect of shock strength on flow features; (4) The effect of shock generator geometry for a given shock strength; (5) Experimental techniques, in particular optical techniques, for the investigation of swept interactions; and (6) Contributions of numerical simulations to the understanding of swept interactions. A limiting factor in the understanding and ability to predict shock wave/boundary-layer interactions is a good knowledge of turbulence behavior. A lecture is devoted specifically to hypersonic interactions."--DTIC.

An experimental study was made of the development of a turbulent boundary layer after an interaction with a normal shock wave (strong enough to cause a local separation) in a strong adverse pressure gradient. This type of flow, which occurs in air breathing engine components (e.g. supersonic intakes, transonic compressor stages and supersonic diffusers), is poorly understood and cannot be satisfactorily predicted. The measurements, made in a closed duct, extended well downstream of the shock wave interaction. Detailed results for the flow are presented and used to support two major conclusions. It is shown that the post shock adverse pressure gradient has a large effect on boundary layer development through the interaction and downstream of it. Consequently existing results for interactions without a post shock pressure gradient should not be used as a model for practical flows which typically have strong pressure gradients applied downstream of the shock wave. The second conclusions was that the shock wave in a rectangular duct produced a pronounced stabilising effect on the downstream flow. Surface flow visualization suggests that this stabilization is achieved by streamwise vortices shed into the flow from the separated region formed by the shock wave. Implications of this result to nominally two-dimensional flow situations and to flows with weak interactions without local separations are discussed.