Download or read book On the Scaling and Unsteadiness of Shock Induced Separation written by Louis Jacques Souverein and published by . This book was released on with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Shock wave boundary layer interactions (SWBLI) are a common phenomenon in transonic and supersonic flows. The presence of shock waves, induced by specific geometrical configurations, cause a rapid increase of the pressure, wich can lead to flow separation. Examples of such interaction are found in amongts other rocket engine nozzles, on re-entry vehicles, in supersonic and hypersonic engine intakes, and at the tips of compressor and turbine blades. The interactions are important factors in vehicle development. Both the separated flow and the induced shock have been shows to be highly unsteady, causing pressure fluctuations and thermal loading. This generally leads to a degraded performance and possibly structural failure. The current work therefore aims to improve the physical understanding of the mechanisms that govern the interaction, with a special attention for the flow organisation and for the sources of the unsteadiness of the induced shock. Additioinally, it is verified wether the interaction can be controlled by means of upstream fluid injection. PIV measurements were performed, comparing several interactions for a range of shock intensities for a number of Mach and Reynolds numbers. It is proposed that relative importance of the different unsteadiness mechanisms (upstream, downstream) shifts with the imposed shock intensity. The onset of separation is Reynolds number independent for turbulent boundary layers. The interaction length is however governed by the both the Reynolds number and the Mach number.

Download or read book Unsteadiness of Shock Induced Turbulent Boundary Layer Separation An Inherent Feature of Turbulent Flow Or Solely a Wind Tunnel Phenomenon written by and published by . This book was released on 1994 with total page 55 pages. Available in PDF, EPUB and Kindle. Book excerpt: The purpose of this work was to (I) examine separation shock wave unsteadiness in different turbulent interactions and determine whether a universal model describing the unsteadiness could be developed, and (II) determine whether or not the observed unsteadiness is a feature of turbulent flow in general, or is specific to the wind tunnel environment. To this end, wall and pitot pressure fluctuation measurements were made in interactions generated by unswept and 25 deg swept compression ramp models, and by 8 deg and 30 deg swept blunt-fin models in a high Reynolds number, Mach 5 turbulent boundary layer. It is clear that the high-frequency, jittery motion of the separation shock is the result of the passage through the wave of individual large-scale turbulent structures. Thus, this component of the unsteadiness is an inherent feature of all turbulent flows. The primary outstanding question concerns the cause of the low-frequency expansion/contraction of the separated flow which is characterized by the large-scale, long-duration excursions of the separation shock wave. Preliminary experimental work to address this question has revealed two very interesting, complementary results. First, there is a distinct correlation between large-scale expansion or contraction of the separated flow and long duration (i.e., low-frequency) falls or rises in pitot pressure in the incoming turbulent boundary layer. Second, results from the same experiment show that the ensemble-averaged pitot pressure at a fixed location in the incoming undisturbed boundary layer correlates with separation shock wave position.

Download or read book Unsteady Effects of Shock Wave induced Separation written by Piotr Doerffer and published by Springer Science & Business Media. This book was released on 2010-11-25 with total page 350 pages. Available in PDF, EPUB and Kindle. Book excerpt: This volume contains description of experimental and numerical results obtained in the UFAST project. The goal of the project was to generate experiment data bank providing unsteady characteristics of the shock boundary layer interaction. The experiments concerned basic-reference cases and the cases with application of flow control devices. Obtained new data bank have been used for the comparison with available simulation techniques, starting from RANS, through URANS, LES and hybrid RANS-LES methods. New understanding of flow physics as well as ability of different numerical methods in the prediction of such unsteady flow phenomena will be discussed.

Download or read book Shock Wave Boundary Layer Interactions written by Holger Babinsky and published by Cambridge University Press. This book was released on 2011-09-12 with total page 481 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.

Download or read book Investigation of Physics of Large Scale Unsteadiness of Shock Induced Turbulent Separation Using Planar Laser Imaging Methods written by and published by . This book was released on 2000 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: This project was aimed at investigating the cause of the low frequency unsteadiness of shock-induced separated flows. This was accomplished by experimentally studying a Mach 5 unswept compression ramp interaction using a combination of planar Imaging diagnostics (namely planar laser scattering and particle image velocimetry (PIV)) and fast response pressure measurements. In particular, PIV was used to investigate the relationship between turbulent velocity fluctuations in the upstream boundary layer and the unsteady separation shock behavior. It was found that positive streamwise velocity fluctuations in the upstream boundary layer correlated with downstream shock motions and negative velocity fluctuations correlated with upstream shock motions. Interestingly, only velocity fluctuations near the wall were correlated with the shock foot motion. These results are coexistent with a simple model wherein a fuller velocity profile provides increased resistance to separation and hence a downstream shock location, and variations in the shape of the velocity profile resulting from turbulent fluctuations yield changes in the shock position and hence produce the unsteady shock foot behavior.

Download or read book Experimental Investigation of Upstream Boundary Layer Acceleration on Unsteadiness of Shock Induced Separation written by and published by . This book was released on 2003 with total page 23 pages. Available in PDF, EPUB and Kindle. Book excerpt: This project was aimed at understanding the fundamental cause of the low frequency unsteadiness present in shock-induced turbulent separated flows. A new multi-camera, multi-laser PIV system was used to capture wide-field images of the velocity field in a Mach 2 compression ramp interaction. The PIV was acquired simultaneously with fast-response pressure measurements to identify the shock-foot location at the same time that the PIV data were captured. The measurements showed that the global structure of the interaction was substantially different depending on the location of the separation shock foot. For example, when the shock is upstream, the scale of the separated flow, the velocity fluctuations and the domain of perturbed flow, are all substantially larger than when the shock-foot is located downstream. Most importantly, a clear correlation was observed between the thickness and velocity profile in the upstream boundary layer and the shock foot position. A new technique for measuring the upstream boundary layer acceleration by using two-frame time-sequenced PIV was also developed. This involved developing new hardware and software tools, and conducting preliminary calibration experiments. This work has shown the feasibility of correlating the upstream acceleration to the shock motion and these measurements will be made in future work.

Download or read book Unsteady Effects of Shock Wave induced Separation written by Piotr Doerffer and published by Springer. This book was released on 2010-12-09 with total page 336 pages. Available in PDF, EPUB and Kindle. Book excerpt: This volume contains description of experimental and numerical results obtained in the UFAST project. The goal of the project was to generate experiment data bank providing unsteady characteristics of the shock boundary layer interaction. The experiments concerned basic-reference cases and the cases with application of flow control devices. Obtained new data bank have been used for the comparison with available simulation techniques, starting from RANS, through URANS, LES and hybrid RANS-LES methods. New understanding of flow physics as well as ability of different numerical methods in the prediction of such unsteady flow phenomena will be discussed.

Download or read book Measurements of a Three dimensional Shock boundary Layer Interaction written by David Benjamin Helmer and published by Stanford University. This book was released on 2011 with total page 212 pages. Available in PDF, EPUB and Kindle. Book excerpt: A series of measurements were taken of the shock-boundary layer interaction (SBLI) in a Mach 2.1 continuously operated wind tunnel. The SBLI was generated by a small (~1.1mm tall) 20° wedge located on the top wall, and data were taken both in the region near the compression wedge and in the area where this shock impinged on the bottom wall. PIV was the primary measurement tool in both locations, though pressure data were also acquired near the compression wedge. Data were acquired at 4 spanwise locations to study the three-dimensionality of the flow. Both interactions were found to be highly 3-D, with a stronger interaction observed near the channel centerline. Evidence of a corner vortical structure in the compression corner was observed, and substantiated by CFD. Intermittent flow reversal was seen in the reflected shock interaction near the channel centerline, though not in the corners. The data suggest the presence of vortical structures generated near the channel centerline and pushed towards the sidewalls. Following the characterization of the base case, a Monte Carlo experiment was performed in which geometric perturbations were installed along the bottom wall of the wind tunnel and their effect on the flow was studied. The Monte Carlo device was designed and installed at the location predicted to be most sensitive by CFD. The majority of the locations initially tested displayed minimal sensitivity, with only the largest and most upstream quasi-2D cases showing significant effects on the flow at the corner. The perturbation device was redesigned and moved upstream, and additional quasi-2D cases were tested. It was found that some configurations accelerated the flow and strengthened the primary shock, while others slowed the flow and weakened the shock. Overall, the flow was observed to be very sensitive to some perturbations, but only to those located within a limited range of streamwise positions, and with a wide variety of system responses possible.

Download or read book Annual Research Briefs written by Center for Turbulence Research (U.S.) and published by . This book was released on 2010 with total page 410 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Unsteady flow organization of a SWBLI written by Raymond A. Humble and published by Eburon Uitgeverij B.V.. This book was released on 2008 with total page 338 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Turbulent Shear Layer Shock Wave Interactions written by J. Delery and published by Springer Science & Business Media. This book was released on 2013-03-08 with total page 434 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.

Download or read book Scientific and Technical Aerospace Reports written by and published by . This book was released on 1995 with total page 456 pages. Available in PDF, EPUB and Kindle. Book excerpt: Lists citations with abstracts for aerospace related reports obtained from world wide sources and announces documents that have recently been entered into the NASA Scientific and Technical Information Database.

Download or read book Physical causes of separation shock unsteadiness in shock wave turbulent boundary layer interactions written by Mehmet Erdal Erengil and published by . This book was released on 1993 with total page 244 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Experimental Characterization and Flowfield Analysis of a Swept Shock Wave Boundary Layer Interaction written by Andrew Kyle Baldwin and published by . This book was released on 2021 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Shockwave boundary layer interactions (SBLI) occur on both internal and external surfaces and adversely affect both the structural and propulsive performance of high-speed flight vehicles operating in the trans/super/hypersonic flow regimes. In the absence of a comprehensive understanding of the flow physics associated with SBLI, the most common approach to mitigating the negative ramifications is structural over-design, often resulting in reduced aero-propulsion efficiencies and excessive cost. SBLI have been the subject of numerous experimental and numerical investigations focusing on simplified two-dimensional (2-D) canonical configurations derived from relatively complicated aircraft/turbomachinery components. A few recent studies have focused on addressing the knowledge gaps by examining component geometries that produce three-dimensional (3-D) SBLI and therefore a closer representation of real-world configurations. The current experimental investigation explores the viscous/inviscid interaction of an incoming supersonic turbulent boundary layer and a single, sharp unswept fin generated shockwave. This kind of SBLI is of keen interest to the high-speed aerodynamics community as the separated flow induces a strong crossflow component, giving rise to a highly 3-D flowfield. Although previous studies on 3-D SBLI have provided a substantial knowledge base, there are still a number of consequential questions pertaining to the flowfield topology and dynamical behavior that remain unanswered. First, what is the effect of Reynolds number on SBLI flow features, in particular, the length scales associated with the shock-induced separation region and its interaction with the shock generator (sharp-fin)? Second, what is the extent of facility dependence on the 3-D SBLI? Which, if any, component(s) of the unsteadiness is inherent to the interaction and which are facility dependent and therefore limit or bias the flowfield? Are the geometric and boundary layer constraints imposed by the size of the facility necessary for numerical simulations to ensure the proper development of scaling parameters as experiments shift from the laboratory scale to flight testing. Finally, how do the spatio-temporal scales associated with SBLI vary with the interaction strength? The main objective of the present experimental study is to answer the posed questions by conducting a detailed flowfield analysis of the sharp fin induced SBLI over a range of Reynolds numbers and interaction strengths. The research methodology involves high-fidelity experiments at the state-of-the-art wind tunnel facilities housed at the Florida Center for Advanced Aero-Propulsion at Florida State University and the data available from previously published literature. Cutting-edge global flowfield diagnostics allow for the full-field reconstruction of both skin friction (mean) and pressure (time-averaged/unsteady) underneath the single fin SBLI as the incoming Mach number (M[infinity] = 2 - 4), fin angle of attack ([alpha]F = 10° - 20°), and unit Reynolds number (Re/m 17 x 106 - 108 x 106) are parametrically varied. Reynolds number sweeps, spanning nearly an order of magnitude, illustrate that the interaction footprint is distinctly affected by the Reynolds number, with the effects being most prominent near the fin/surface junction and the outer edges of the interaction near the freestream boundary. The results indicate that the interaction flowfield becomes less receptive to Reynolds number variations as the Reynolds number continues to increase. This shrinking dependence indicates that there may be a point beyond which any further increases to the Reynolds number produce negligible differences in the flowfield id est Reynolds number independence. Identical surface oil flow and pressure measurements carried out in facilities of different scale/size compare favorably throughout the interaction region with Reynolds number based scaling. However, different incoming boundary layer thicknesses impose limitations on the extent of the inception region and the onset of finite fin effects. When investigating the mean skin friction between different scale facilities, the Reynolds number scaling could not be assessed due to limitations of the available data sets. An angular scaling was applied to enable proper inter-facility comparison between the conical regions of both identically matching and nominally equivalent interaction strength test cases. The results showed trends similar to those seen in the pressure measurements, with skin friction matching well between the facilities across the interaction with minor divergences in the near fin region, where viscous effects become more prominent. Simultaneously sampled high-speed pressure transducers and fast response PSP measurements allowed for a full-field investigation of the flow dynamics. The RMS pressure field highlights regions of increased unsteadiness along the interaction boundary, inviscid shock line and at/upstream of the fin tip vertex. Increased coherence levels indicate a communication mechanism is present between the inviscid shock and the interaction boundary. When compared with studies conducted in a smaller facility, findings of the current work are consistent in both the locations of increased unsteadiness and their respective magnitudes. In addition to illustrating the robustness of these dynamical features between differing size facilities, the current work identifies the presence of elevated levels of low-frequency content. The presence of this low-frequency content has been observed in investigations associated with 2-D SBLI, but has been absent in the 3-D SBLI studies conducted in smaller facilities. The present study has contributed significantly to a better understanding of swept 3-D SBLI, in particular, the role of Reynolds number and the size of facility on the interaction characteristics. The flowfield analysis has discovered the underlying physics associated with the fin induced SBLI. The high-fidelity experimental database generated will be very useful for the validation of numerical tools and the development of flight vehicle design guidelines.

Download or read book Aeronautical Engineering written by and published by . This book was released on 1991 with total page 538 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book New Results in Numerical and Experimental Fluid Mechanics III written by Siegfried Wagner and published by Springer Science & Business Media. This book was released on 2002-02-26 with total page 458 pages. Available in PDF, EPUB and Kindle. Book excerpt: This volume contains the papers of a German symposium dealing with research and project work in numerical and experimental aerodynamics and fluidmechanics for aerospace and other applications. It gives a broad overview over the ongoing work in this field in Germany.

Download or read book Issues in Aerospace and Defense Research and Application 2011 Edition written by and published by ScholarlyEditions. This book was released on 2012-01-09 with total page 385 pages. Available in PDF, EPUB and Kindle. Book excerpt: Issues in Aerospace and Defense Research and Application: 2011 Edition is a ScholarlyEditions™ eBook that delivers timely, authoritative, and comprehensive information about Aerospace and Defense Research and Application. The editors have built Issues in Aerospace and Defense Research and Application: 2011 Edition on the vast information databases of ScholarlyNews.™ You can expect the information about Aerospace and Defense Research and Application in this eBook to be deeper than what you can access anywhere else, as well as consistently reliable, authoritative, informed, and relevant. The content of Issues in Aerospace and Defense Research and Application: 2011 Edition has been produced by the world’s leading scientists, engineers, analysts, research institutions, and companies. All of the content is from peer-reviewed sources, and all of it is written, assembled, and edited by the editors at ScholarlyEditions™ and available exclusively from us. You now have a source you can cite with authority, confidence, and credibility. More information is available at http://www.ScholarlyEditions.com/.