Download or read book Control of Mean Separation in a Compression Ramp Shock Boundary Layer Interaction Using Pulsed Plasma Jets written by Benton Robb Greene and published by . This book was released on 2014 with total page 100 pages. Available in PDF, EPUB and Kindle. Book excerpt: Pulsed plasma jets (also called "SparkJets'") were investigated for use in controlling the mean separation location induced by shock wave-boundary layer interaction. These synthetic jet actuators are driven by electro-thermal heating from an electrical discharge in a small cavity, which forces the gas in the cavity to exit through a small hole as a high-speed jet. With this method of actuation, pulsed plasma jets can achieve pulsing frequencies on the order of kilohertz, which is on the order of the instability frequency of many lab-scale shock wave-boundary layer interactions (SWBLI). The interaction under investigation was generated by a 20° compression ramp in a Mach 3 flow. The undisturbed boundary layer is transitional with Re[subscript theta] of 5400. Surface oil streak visualization is used in a parametric study to determine the optimum pulsing frequency of the jet, the optimum distance of the jet from the compression corner, and the optimum injection angle of the jets. Three spanwise-oriented arrays of three plasma jets are tested, each with a different pitch and skew angle on the jet exit port. The three injection angles tested were 22° pitch and 45° skew, 20° pitch and 0° skew, and 45° pitch and 0° skew. Jet pulsing frequency is varied between 2 kHz and 4 kHz, corresponding to a Strouhal number based on separation length of 0.012 and 0.023. Particle image velocimetry is used to characterize the effect that the actuators have on the reattached boundary layer profile on the ramp surface. Results show that plasma jets pitched at 20° from the wall, and pulsed at a Strouhal number of 0.018, can reduce the size of an approximate measure of the separation region by up to 40% and increase the integrated momentum in the downstream reattached boundary layer, albeit with a concomitant increase in the shape factor.
Download or read book Investigation of a Pulsed plasma Jet for Separation Shock boundary Layer Interaction Control written by Venkateswa Narayanaswamy and published by . This book was released on 2010 with total page 428 pages. Available in PDF, EPUB and Kindle. Book excerpt: A pulsed-plasma jet (called a "spark-jet" by other researchers), is a high-speed synthetic jet that is generated by striking an electrical discharge in a small cavity. The gas in the cavity pressurizes owing to the heating and is allowed to escape through a small orifice. A series of experiments were conducted to determine the characteristics of the pulsed-plasma jet issuing into stagnant air at a pressure of 45 Torr. These results show that typical jet exit velocities of about 250 m/s can be induced with discharge energies of about 30 mJ per jet. Furthermore, the maximum pulsing frequency was found to be about 5 kHz, because above this frequency the jet begins to misfire. The misfiring appears to be due to the finite time it takes for the cavity to be recharged with ambient air between discharge pulses. The velocity at the exit of the jet is found to be primarily dependent on the discharge current and independent of other discharge parameters such as cavity volume and orifice diameter. Temperature measurements are made using optical emission spectroscopy and reveal the presence of considerable non-equilibrium between rotational and vibrational modes. The gas heating efficiency was found to be 10% and this parameter is shown to have a direct effect on the plasma jet velocity. These results indicate that the pulsed-plasma jet creates a sufficiently strong flow perturbation that is holds great promise as a supersonic flow actuator. An experimental study is conducted to characterize the performance of a pulsed-plasma jet for potential use in supersonic flow control applications. To obtain an estimate of the relative strength of the pulsed-plasma jet, the jet is injected normally into a Mach 3 cross-flow and the penetration distance is measured by using schlieren imaging. These measurements show that the jet penetrates 1.5 [delta], where [delta] is the boundary layer thickness, into the cross-flow and the jet-to-crossflow momentum flux ratio is estimated to be 0.6. An array of pulsed-plasma jets was issued from different locations upstream of a 30-degree compression ramp in a Mach 3 flow. Furthermore, two different jet configurations were used: normal injection and pitched and skewed injection. The pitched and skewed configuration was used to see if the jets could act as high-bandwidth pulsed vortex generators. The interaction between the jets and the separation shock was studied using phase-locked schlieren imaging. Results show that the plasma jets cause a significant disturbance to the separation shock and clearly influence its unsteadiness. While all plasma jet configurations tested caused an upstream motion of the separation shock, pitched and skewed plasma jets caused an initial downstream shock motion before the upstream motion, demonstrating the potential use of these plasma jets as vortex generator jets. The effect of the plasma jet array on the separation shock unsteadiness is studied in a time-resolved manner by using 10 kHz schlieren imaging and fast-response wall pressure measurements. An array of three pulsed-plasma jets, in a pitched and skewed configuration, is used to force the unsteady motion of the interaction formed by a 24° compression ramp in a Mach 3 flow. The Reynolds number of the incoming boundary layer is Re[theta]=3300. Results show that when the pulsed jet array is placed upstream of the interaction, the jets cause the separation shock to move in a quasi-periodic manner, i.e., nearly in sync with the pulsing cycle. As the jet fluid convects across the separation shock, the shock responds by moving upstream, which is primarily due to the presence of hot gas and hence the lower effective Mach number of the incoming flow. Once the hot gases pass through the interaction, the separation shock recovers by moving downstream, and this recovery velocity is approximately 1% to 3% of the free stream velocity. With forcing, the low-frequency energy content of the pressure fluctuations at a given location under the intermittent region decreases significantly. This is believed to be a result of an increase in the mean scale of the interaction under forced conditions. Pulsed-jet injection are also employed within the separation bubble, but negligible changes to the separation shock motion were observed. These results indicate that influencing the dynamics of this compression ramp interaction is much more effective by placing the actuator in the upstream boundary layer.
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 Compressibility Turbulence and High Speed Flow written by Thomas B. Gatski and published by Academic Press. This book was released on 2013-03-05 with total page 343 pages. Available in PDF, EPUB and Kindle. Book excerpt: Compressibility, Turbulence and High Speed Flow introduces the reader to the field of compressible turbulence and compressible turbulent flows across a broad speed range, through a unique complimentary treatment of both the theoretical foundations and the measurement and analysis tools currently used. The book provides the reader with the necessary background and current trends in the theoretical and experimental aspects of compressible turbulent flows and compressible turbulence. Detailed derivations of the pertinent equations describing the motion of such turbulent flows is provided and an extensive discussion of the various approaches used in predicting both free shear and wall bounded flows is presented. Experimental measurement techniques common to the compressible flow regime are introduced with particular emphasis on the unique challenges presented by high speed flows. Both experimental and numerical simulation work is supplied throughout to provide the reader with an overall perspective of current trends. - An introduction to current techniques in compressible turbulent flow analysis - An approach that enables engineers to identify and solve complex compressible flow challenges - Prediction methodologies, including the Reynolds-averaged Navier Stokes (RANS) method, scale filtered methods and direct numerical simulation (DNS) - Current strategies focusing on compressible flow control
Download or read book Understanding Micro Ramp Control for Shock Boundary Layer Interactions written by and published by . This book was released on 2008 with total page 29 pages. Available in PDF, EPUB and Kindle. Book excerpt: Micro-vortex generators (micro-VGs) have the ability to alter the near-wall structure of compressible turbulent boundary layers in such a way that the flow becomes significantly less susceptible to separations and more stable to unsteady disturbances. Due to their extremely small size, micro-VGs are embedded in the boundary layer and may provide reduced viscous drag when compared to traditional vortex generators. Of several candidate micro-VGs, micro-ramps have been found to significantly impact shock boundary layer interaction flows, while being cost-effective, physically robust, and requiring no power sources. Thus detailed study of flow interactions with micro-ramps on a supersonic boundary layer at M=3.0 was investigated using monotone integrated Large Eddy Simulations (MILES) and Reynolds Averaged Navier-Stokes (RANS). A rescale-recycle method was used to efficiently generate turbulent in-flow conditions. Studies showed that the vortical structure generated from the micro-ramp flows through the separation region caused by the impinging shock, which helped to reduce the area of separation.
Download or read book Scientific and Technical Aerospace Reports written by and published by . This book was released on 1992 with total page 1556 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Flow Control Techniques and Applications written by Jinjun Wang and published by Cambridge University Press. This book was released on 2019 with total page 293 pages. Available in PDF, EPUB and Kindle. Book excerpt: Master the theory, applications and control mechanisms of flow control techniques.
Download or read book Control of Shock Wave boundary Layer Interactions by Bleed in Supersonic Mixed Compression Inlets written by Michael K. Fukuda and published by . This book was released on 1975 with total page 148 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book International Aerospace Abstracts written by and published by . This book was released on 1999 with total page 1044 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Transition Location Effect on Shock Wave Boundary Layer Interaction written by Piotr Doerffer and published by Springer. This book was released on 2021-08-01 with total page 540 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book presents experimental and numerical findings on reducing shock-induced separation by applying transition upstream the shock wave. The purpose is to find out how close to the shock wave the transition should be located in order to obtain favorable turbulent boundary layer interaction. The book shares findings obtained using advanced flow measurement methods and concerning e.g. the transition location, boundary layer characteristics, and the detection of shock wave configurations. It includes a number of experimental case studies and CFD simulations that offer valuable insights into the flow structure. It covers RANS/URANS methods for the experimental test section design, as well as more advanced techniques, such as LES, hybrid methods and DNS for studying the transition and shock wave interaction in detail. The experimental and numerical investigations presented here were conducted by sixteen different partners in the context of the TFAST Project. The general focus is on determining if and how it is possible to improve flow performance in comparison to laminar interaction. The book mainly addresses academics and professionals whose work involves the aerodynamics of internal and external flows, as well as experimentalists working with compressible flows. It will also be of benefit for CFD developers and users, and for students of aviation and propulsion systems alike.
Download or read book Passive Control of Normal Shock boundary Layer Interaction Using Aeroelastic Mesoflaps written by Martin Johannes Orphanides and published by . This book was released on 2003 with total page 390 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Experiments on Normal Shock boundary Layer Interaction Control Using Aeroelastic Mesoflaps written by Everett Shingo Hafenrichter and published by . This book was released on 2001 with total page 282 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book The Boundary Layer in the Confinement of a One dimensional Plasma written by W. Paskievici and published by . This book was released on 1962 with total page 48 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Active and Passive Shock Boundary Layer Interaction Control on Supercritical Airfoils written by P. Thiede and published by . This book was released on 1984 with total page 13 pages. Available in PDF, EPUB and Kindle. Book excerpt: This paper presents experimental investigations which aimed at improving the off-design performance of supercritical airfoils by active or passive control of the shock/boundary layer interaction (SBLI) through boundary layer suction in the shock region or ventilation respectively. The experiments were carried out in the DFVLR 1m x 1m transonic windtunnel Gottingen, using the advanced supercritical airfoil VFW VA-2 designed to have a largely fixed shock position at off-design conditions. The basic model was equipped with an exchangeable control device within the shock region to allow measurements with either surface clean, suction through a single slot, double slot or perforated strip or ventilation through a double slot or perforated strip. The effectiveness of the different SBLI control methods is evaluated from surface pressure distribution, wake and boundary layer measurements as well as Schlieren observations. It is shown that local boundary suction in the shock region mainly delays the shock-induced separation to greater shock strength and stabilizes the shock in its rearward position up to higher incidence, resulting in substantial improvements in the airfoil characteristics at off-design conditions. Moreover, without any suction, favorable passive effect is observed by boundary layer ventilation on the double slot and perforated strip configurations with a plenum underneath. This leads to a weakening of the shock wave, offering a large potential for off-design drag reduction.
Download or read book Enhanced Design of Turbo Jet LPT by Separation Control Using Phased Plasma Actuators written by and published by DIANE Publishing. This book was released on 2003 with total page 25 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Asymptotic Theory of Separation and Reattachment of a Laminar Boundary Layer on a Compression Ramp written by O. R. Burggraf and published by . This book was released on 1975 with total page 12 pages. Available in PDF, EPUB and Kindle. Book excerpt: Laminar boundary layer separation and reattachment are considered for adiabatic flow over a compression ramp with a supersonic mainstream. For a large ramp angle, calculations based on the Stewartson-Williams triple-deck theory show that the regions of separation and reattachment become distinct, with an intervening plateau region of nearly constant pressure. The mathematical description of each of these distinct regions is given, and simple formulas derived for a number of quantities of interest, including the plateau pressure, conditions at separation and reattachment, and the geometry of the separated region. The theory should provide a useful tool for engineering analysis.
