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Book Control of Supersonic Mixed compression Inlets Using Localized Arc Filament Plasma Actuators

Download or read book Control of Supersonic Mixed compression Inlets Using Localized Arc Filament Plasma Actuators written by Nathan Joseph Webb and published by . This book was released on 2010 with total page 80 pages. Available in PDF, EPUB and Kindle. Book excerpt: Abstract: Shock wave/boundary layer interactions (SWBLIs) occur in many supersonic internal flow applications, specifically in mixed compression inlets, as well as in external flows. In this study a nominally Mach 2 mixed compression inlet is modeled by two experimental setups: 1) A compression ramp-generated impinging SWBLI, and 2) a variable angle wedge (VAW) generated impinging SWBLI. The compression ramp and the wedge both serve to generate an oblique shock wave that impinges on the boundary layer on the opposite surface of the wind tunnel. This produces an impinging SWBLI within the test section that replicates the flow found in a mixed compression inlet. A SWBLI can cause flow separation and it is desirable to efficiently prevent this to avoid the many adverse consequences that may result otherwise. The goal of this study is to investigate the ability of localized arc-filament plasma actuators (LAFPAs) to effectively control the interaction. The LAFPAs show significant ability to beneficially affect the SWBLI depending on various operating parameters such as geometry and forcing Strouhal number. This ability apparently stems from a manipulation of instabilities naturally present in the flow. For the compression ramp facility the LAFPAs were most effective when located upstream of the shock foot, forcing with a Strouhal number of 0.03, and operated in-phase. The VAW facility is currently being debugged and will be used for future detailed experiments investigating the control authority of the LAFPAs.

Book Control of the Interaction Between an Oblique Shock Wave and a Supersonic Turbulent Boundary Layer by Localized Arc Filament Plasma Actuators

Download or read book Control of the Interaction Between an Oblique Shock Wave and a Supersonic Turbulent Boundary Layer by Localized Arc Filament Plasma Actuators written by Nathan J. Webb and published by . This book was released on 2009 with total page 36 pages. Available in PDF, EPUB and Kindle. Book excerpt: Abstract: The ability of localized arc filament plasma actuators to eliminate or reduce the extent of boundary layer separation in the interaction between an oblique shock wave and a turbulent boundary layer is examined. This is an important phenomenon occurring in many applications including supersonic aircraft engine inlets. The effects of the actuators on the flow were studied for varying frequency, location, and mode of actuation of the actuators. The effectiveness of the forcing was determined by using schlieren imaging techniques, particle image velocimetry, and unsteady pressure measurements. The data collected shows that the actuators do have significant effects on the flow and can effectively remove the separation caused by the shock wave/boundary layer interaction.

Book Design and Characterization of a Supersonic Wind Tunnel for the Study of Shock Wave Boundary Layer Interactions

Download or read book Design and Characterization of a Supersonic Wind Tunnel for the Study of Shock Wave Boundary Layer Interactions written by Christopher J. Clifford and published by . This book was released on 2010 with total page 50 pages. Available in PDF, EPUB and Kindle. Book excerpt: Abstract: A new 3"x3" supersonic wind tunnel was built to facilitate the continued development of localized arc filament plasma actuators (LAFPAs) as a control method for supersonic mixed compression inlets. A variable angle wedge was employed as the compression surface to generate a variable strength shock wave boundary layer interaction (SWBLI). The resulting flow is Mach 2.33 with a Reynolds number based on boundary layer momentum thickness of 23,000. Several qualitative techniques were used to observe certain aspects of the flow and interaction. Schlieren imaging was used during the troubleshooting phase to identify extraneous shock waves and expansion waves and revealed an unwanted separation region on the ceiling. Oil flow visualization on the interaction surface highlights the three-dimensionality of the separation region, but also confirms a two-dimensional assumption near the centerline of the tunnel. The separation region was found to extend 20 mm in the streamwise direction. Particle image velocimetry (PIV) was used to gather quantitative flow field information about the freestream and boundary layer. The incoming boundary layer, measuring 4.62 mm in thickness, will be analyzed in further detail.

Book Active Control of Supersonic Jets Operating in Various Flow Regimes

Download or read book Active Control of Supersonic Jets Operating in Various Flow Regimes written by Robert Michael Snyder and published by . This book was released on 2008 with total page 300 pages. Available in PDF, EPUB and Kindle. Book excerpt: Abstract: The flow through the exhaust nozzle of a jet engine has been of crucial importance in aerospace applications over the past several decades. A variety of modifications can be made to the nozzles of high-speed jet engines to increase or decrease mixing between the exiting flow and the ambient air; including adding tabs, chevrons, or actuators. Localized arc filament plasma actuators (LAFPAs) developed in the Gas Dynamics and Turbulence Laboratory at The Ohio State University have both high amplitude and bandwidth and are suitable for active control of high-speed, high Reynolds number flows. LAFPAs were used to control a supersonic jet from an axisymmetric nozzle of design Mach number of 1.3 operating from overexpanded to underexpanded flow regimes with the fully expanded jet Mach number (MJ) from 1.1 to 1.5 in order to explore their characteristics and their potential for mixing enhancement between the jet and the ambient air. The Reynolds number based on the 2.54 cm nozzle exit diameter was from 1.0x106 to 1.4x106. Laser based planar flow visualizations, schlieren imaging, and particle image velocimetry measurements were used to evaluate the effects of control. Results show the effects of forcing frequency and other parameters on the development of large-scale structures within the flow. Eight actuators, distributed azimuthally approximately 1 mm upstream of the nozzle exit, were used to force various azimuthal modes over a large Strouhal number range (StDF of 0.07 to 2.68). The preliminary results in underexpanded jets (MJ = 1.4 and 1.5) were quite similar to results in the ideally expanded jet (MJ = 1.3) previously obtained in similar studies at GDTL. The ideally expanded jet responded to the forcing over the entire range of frequencies, but the response was optimum (in terms of development of large coherent structures and mixing enhancement) around the jet preferred Strouhal number of 0.34 (fF = 5 kHz). Similarly, the optimum response was found at a jet preferred Strouhal number of 0.27 (fF = 4 kHz) for the slightly underexpanded jet (MJ = 1.4) and 0.34 (fF = 5 kHz) for the strongly underexpanded jet (MJ = 1.5). The jet also responded to forcing with various azimuthal modes (m=0 to 3 and m= ± 1, ±2, ±4). Forcing the jet with the azimuthal mode m= ±1 at the jet preferred mode frequency provided the maximum mixing enhancement in the visualized plane. Conversely, the preliminary results showed that the overexpanded jets (MJ = 1.1 and 1.2) did not respond at all or the response was relatively small. Subsequent surface pressure measurements with an extension without actuators revealed significant pressure increases near the nozzle exit for the strongly overexpanded MJ = 1.1 case, suggesting the existence of flow separation. Flow separation would cause the flow to pass over actuator location, thus nullifying the effect of control.

Book Active Control of High Speed Subsonic Cavity Flow Using Plasma Actuators

Download or read book Active Control of High Speed Subsonic Cavity Flow Using Plasma Actuators written by Douglas Alan Mitchell and published by . This book was released on 2007 with total page 242 pages. Available in PDF, EPUB and Kindle. Book excerpt: Abstract: The study and control of cavity flow fields began in the 1950's and has remained an active area of research for the past fifty years. Grazing flow over an open cavity which leads to resonance is a common occurrence generated by the flow-acoustic coupling mechanism. When the natural instabilities in the shear layer phase match with the acoustic waves generated from the impingement of the structures in the shear layer at the trailing edge of the cavity, high amplitude background noise and discrete cavity tones are generated in the form of high amplitude pressure fluctuations. Common examples of this phenomenon are aircraft landing gear openings, aircraft weapons bays, and engine air intakes. Unchecked cavity flow resonance can lead to weapon stores damage and incorrect deployment, reduction in lift, increase in drag, and structural fatigue. Initial research concentrated on using a compression driver as a synthetic jet type actuator to reduce acoustic resonance peaks, to operate the actuator at optimal forcing frequencies using reduced order modeling in order to shrink the peaks without triggering adjacent tones, and to develop logic based controls to damp pressure fluctuations within the system. The compression driver was ultimately limited by its frequency bandwidth and power output. The limited capabilities of the compression driver led to the development of the localized arc filament plasma actuator which is capable of high bandwidth and high amplitude actuation. The focus of this research was on the development of a high speed subsonic cavity flow facility and its control using localized arc filament plasma actuators (LAFPA). A cavity flow facility was designed and fabricated which allowed for the study of both baseline and forced cavity flows. The baseline flow characteristics were studied using flow visualization techniques in the form of particle image velocimetry (PIV) and schlieren photography, dynamic surface pressure measurements, and instantaneous and time-averaged dynamic pressure correlations to gain further understanding in cavity flow physics. Once the flow was sufficiently understood, LAFPAs were then used to force the flow into different modes or non-preferred frequencies in order to reduce the cavity tones or reduce the overall sound pressure level. Resonant, non-resonant, and multi-mode resonance are studied and actuated at various forcing frequencies, duty cycles, and modes. Furthermore, several different plasma actuator platforms were developed and tested to determine an optimal electrode arrangement during actuation.

Book A Supersonic Inlet engine Control Using Engine Speed as a Primary Variable for Controlling Normal Shock Position

Download or read book A Supersonic Inlet engine Control Using Engine Speed as a Primary Variable for Controlling Normal Shock Position written by Francis J. Paulovich and published by . This book was released on 1971 with total page 52 pages. Available in PDF, EPUB and Kindle. Book excerpt: A cross-coupled inlet-engine control system concept is presented for a supersonic propulsion system consisting of a mixed- compression inlet and a turbojet engine. The control system employs manipulation of both bypass door flow area and engine speed to stabilize normal shock position in the inlet. Specifically, the case of slow-acting bypass doors used as a reset control where engine speed is the primary means of shock position control is described. Experimental results are presented showing performance of the control system with a NASA-designed inlet and a turbojet engine operating at Mach 2.5 in the Lewis 10- by 10-Foot Supersonic Wind Tunnel.

Book Experimental Investigation of a Large scale Two dimensional Mixed compression Inlet System

Download or read book Experimental Investigation of a Large scale Two dimensional Mixed compression Inlet System written by Norman D. Wong and published by . This book was released on 1971 with total page 68 pages. Available in PDF, EPUB and Kindle. Book excerpt: A large-scale, variable-geometry inlet model with a design Mach number of 3.0 was tested at Mach numbers from 1.55 to 3.2. Variable features of the inlet for off-design operation are an adjustable-height ramp system and a translating cowl. This report presents experimental results for a diffuser and boundary-layer bleed configuration which was optimized at the design Mach number. Overall performance was high with throat-mounted vortex generators, which were effective in reducing flow distortion in the subsonic diffuser at the higher Mach numbers.

Book Coupled Supersonic Inlet engine Control Using Overboard Bypass Doors and Engine Speed to Control Normal Shock Position

Download or read book Coupled Supersonic Inlet engine Control Using Overboard Bypass Doors and Engine Speed to Control Normal Shock Position written by Gary L. Cole and published by . This book was released on 1970 with total page 44 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Book Shock Wave Boundary Layer Interactions

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.

Book Suppression of Cavity Driven Flow Separation in a Simulated Mixed Compression Inlet

Download or read book Suppression of Cavity Driven Flow Separation in a Simulated Mixed Compression Inlet written by National Aeronautics and Space Administration (NASA) and published by Createspace Independent Publishing Platform. This book was released on 2018-06-16 with total page 38 pages. Available in PDF, EPUB and Kindle. Book excerpt: A test facility designed to simulate a bifurcated subsonic diffuser operating within a mixed compression inlet is described. The subsonic diffuser in this facility modeled a bypass cavity feature often used in mixed compression inlets for engine flow matching and normal shock control. A bypass cavity-driven flow separation was seen to occur in the subsonic diffuser without applied flow control. Flow control in the form of vortex generators and/or a partitioned bypass cavity cover plate were used to eliminate this flow separation, providing a 2% increase in area-averaged total pressure recovery, and a 70% reduction in circumferential distortion intensity. Wendt, Bruce J. Glenn Research Center NASA/CR-2000-210460, E-12456, NAS 1.26:210460