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Active Control Of Supersonic Jets Operating In Various Flow Regimes
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Book Synopsis Active Control of Supersonic Jets Operating in Various Flow Regimes by : Robert Michael Snyder
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 Synopsis Active Control of Supersonic Impinging Jets Using Supersonic Microjets by : Farrukh S. Alvi
Download or read book Active Control of Supersonic Impinging Jets Using Supersonic Microjets written by Farrukh S. Alvi and published by . This book was released on 2005 with total page 72 pages. Available in PDF, EPUB and Kindle. Book excerpt: A comprehensive experimental investigation on the use of microjets for the control of supersonic impinging jets was conducted under this research program. Supersonic impinging jets occur in many applications including in STOVL aircraft where they lead to a highly oscillatory flow with very high unsteady loads on the nearby aircraft structures and the landing surfaces. Prior research has shown that microjets, placed around the main jet periphery, are very effective in reducing the flow unsteadiness and the associated dynamic loads. In the present work, our goal was to better understand the physical properties of supersonic impinging jets through detailed experiments and to develop optimal open and closed-loop control strategies in order to produce efficient control over the range of conditions impinging jet-related problems are significant.
Book Synopsis Active Control of Supersonic Impinging Jets by : A. Krothapalli
Download or read book Active Control of Supersonic Impinging Jets written by A. Krothapalli and published by . This book was released on 2001 with total page 10 pages. Available in PDF, EPUB and Kindle. Book excerpt: Experimental studies of supersonic impinging jet flows suggest that they are greatly influenced by the flow-acoustic interactions through a feedback mechanism. The self-sustained oscillations of the jet column observed in theses flows result in high velocities in the ambient medium induced by the large-scale coherent vortical structures in the jet shear layers. As a consequence, the suck down force on the surface from which the jet is issuing can reach as high as 60% of the primary jet thrust. In addition, the overall sound pressure level (OASPL), increase significantly relative to a free jet. To alleviate these undesirable flow and acoustic characteristics, a novel control technique using supersonic microjets is demonstrated. Sixteen supersonic microjets are placed around the circumference of the main jet at the nozzle exit to disrupt the feedback mechanism. As a result, significant lift loss recovery( -50%) and reduced near field OASPL ( -7dB) are observed.
Book Synopsis Active Control of High Reynolds Number Supersonic Jets Using Plasma Actuators by :
Download or read book Active Control of High Reynolds Number Supersonic Jets Using Plasma Actuators written by and published by . This book was released on 2010 with total page 65 pages. Available in PDF, EPUB and Kindle. Book excerpt: Active flow control of jets with Localized Arc Filament Plasma Actuators (LAFPAs) is conducted over a wide range of the fully expanded jet Mach numbers (M(J) or simply jet Mach number). The jet Mach numbers covered in the present research are 0.9 (with a converging nozzle), 1.2 (overexpanded), 1.3 (perfectly expanded), and 1.4 (underexpanded) with a design Mach number 1.3. Additionally, limited experiments are carried out for an M(J) = 1.65 perfectly-expanded jet. The exit diameter is 2.54 cm (1 inch) for all cases and eight LAFPAs are equally distributed on the perimeter of a boron nitride nozzle extension. The jet spreading is strongly dependent on duty cycle, forcing frequency, and azimuthal modes. The performance of LAFPAs for jet spreading is investigated using two-dimensional particle image velocimetry (PIV). There is an optimum duty cycle, producing maximum jet spreading, for each forcing frequency. A relationship between the optimum duty cycle and forcing frequency is determined from the extensive results in the MJ 0.9, and this relation is used for all experiments. The effect of forcing frequency is investigated for a wide range of forcing Strouhal numbers (StDF = f(F)D/U(e), where f(F), D, and U(e), are forcing frequency, nozzle exit diameter, and jet exit velocity respectively), ranging from 0.09 to 3.0. The azimuthal modes (m) investigated are m = 0 - 3, +/-1, +/-2, and +/-4 - this comprises all modes available with eight actuators. The performance of LAFPAs does also strongly depend on the stagnation temperature of the jet and M(J). The effects of stagnation temperature are investigated for 1.0, 1.4, and 2.0 times the ambient temperature in M(J) 0.9 jet for very limited azimuthal modes and St(DF). In an M(J) 1.65 perfectly-expanded jet, the control authority of LAFPAs is investigated for only m = +/-1 and St(DF) tilde 0.3.
Book Synopsis Critical Regimes of Supersonic Jet Aircraft by : Mikhail Grigorʹevich Kotik
Download or read book Critical Regimes of Supersonic Jet Aircraft written by Mikhail Grigorʹevich Kotik and published by . This book was released on 1969 with total page 228 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Active Control of Supersonic Impinging Jets Using Supersonic Microjets by :
Download or read book Active Control of Supersonic Impinging Jets Using Supersonic Microjets written by and published by . This book was released on 2003 with total page 144 pages. Available in PDF, EPUB and Kindle. Book excerpt: Supersonic impinging jet flows, such as those that occur in the next generation of STOVL aircraft, are highly unsteady due to the presence a feedback loop. This results in large dynamic loads on the nearby aircraft structures and surfaces and diminishes aircraft performance. In this study, a unique active control technique that utilizes arrays of supersonic microjets (less than or equal 400 micrometers) around the periphery of the main jet was examined. The efficacy of microjet control was explored over a large parametric range. This control approach was very successful and the activation of the microjets led to dramatic reductions in ground effect. The lift loss was reduced by up to 40%, while the unsteady loads were reduced by as much as 12 dB. These dramatic gains in performance were achieved with negligible microjet mass flux (less than 0.5%). A detailed study of this flow was conducted to better understand the governing flow physics. The velocity field data clearly indicates that the activation of microjets generates significant streamwise vorticity while reducing the azimuthal vorticity of the primary jet It is proposed that the streamwise vorticity is mainly a result of the redirection of the azimuthal vorticity, which weakens the large-scale structures in the primary jet. This is considered to be a primary factor in the efficient disruption of the feedback loop. A new, POD-based, closed-loop control strategy, is also explored in order to achieve optimal and uniform control. The closed-loop control results led to an improvement in the control efficiency compared to the open-loop strategy in a number of cases.
Book Synopsis Scientific and Technical Aerospace Reports by :
Download or read book Scientific and Technical Aerospace Reports written by and published by . This book was released on 1995 with total page 400 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Active Control of Supersonic Impinging Jets by : H. Lou
Download or read book Active Control of Supersonic Impinging Jets written by H. Lou and published by . This book was released on 2002 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Compressibility, Turbulence and High Speed Flow by : Thomas B. Gatski
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
Book Synopsis Flight Stability and Automatic Control by : Robert C. Nelson
Download or read book Flight Stability and Automatic Control written by Robert C. Nelson and published by WCB/McGraw-Hill. This book was released on 1998 with total page 441 pages. Available in PDF, EPUB and Kindle. Book excerpt: The second edition of Flight Stability and Automatic Control presents an organized introduction to the useful and relevant topics necessary for a flight stability and controls course. Not only is this text presented at the appropriate mathematical level, it also features standard terminology and nomenclature, along with expanded coverage of classical control theory, autopilot designs, and modern control theory. Through the use of extensive examples, problems, and historical notes, author Robert Nelson develops a concise and vital text for aircraft flight stability and control or flight dynamics courses.
Book Synopsis Active Control Strategies to Optimize Supersonic Fuel-Air Mixing for Combustion Associated with Fully Modulated Transverse Jet in Cross Flow by :
Download or read book Active Control Strategies to Optimize Supersonic Fuel-Air Mixing for Combustion Associated with Fully Modulated Transverse Jet in Cross Flow written by and published by . This book was released on 2005 with total page 63 pages. Available in PDF, EPUB and Kindle. Book excerpt: A 76 mm x 76 mm supersonic wind tunnel with variable Mach Numbers (M = 1.5 - 4) was designed and set up. The wind tunnel could support both non-reacting fuel-air mixing and combustion. A back pressure flap was added at the downstream end of the diffuser for dual mode (subsonic- supersonic) combustion studies. A high-speed imaging system was used for the visualization of pure liquid jet, aerated liquid jet and pulsed aerated jet injection into a supersonic cross flow at Mach number 1.5. The penetration height of the jet was determined from the average of 100 instantaneous recorded images. For the aerated jet the gas-liquid mass ratio varied from 0 to 8.2% for water and from 0 to 9.9% for methanol. For the pulsed aerated jet, the aerating gas was pulsed with a frequency range 1 - 1000 Hz at a constant duty cycle of 50% and at 1000 Hz with a variable duty cycle between 0 and 100%. Results were reported in correlations.
Download or read book The Aeronautical Journal written by and published by . This book was released on 2001 with total page 732 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Commercial Supersonic Technology by : National Research Council
Download or read book Commercial Supersonic Technology written by National Research Council and published by National Academies Press. This book was released on 2002-02-16 with total page 128 pages. Available in PDF, EPUB and Kindle. Book excerpt: High-speed flight is a major technological challenge for both commercial and business aviation. As a first step in revitalizing efforts by the National Aeronautics and Space Administration (NASA) to achieve the technology objective of high-speed air travel, NASA requested the National Research Council (NRC) to conduct a study that would identify approaches for achieving breakthroughs in research and technology for commercial supersonic aircraft. Commercial Supersonic Technology documents the results of that effort. This report describes technical areas where ongoing work should be continued and new focused research initiated to enable operational deployment of an environmentally acceptable, economically viable commercial aircraft capable of sustained supersonic flight, including flight over land, at speeds up to approximately Mach 2 in the next 25 years or less.
Download or read book NASA Tech Briefs written by and published by . This book was released on 1992-05 with total page 76 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Active Control of Supersonic Impingement Tones Using Microjets by : Jae Jeen Choi
Download or read book Active Control of Supersonic Impingement Tones Using Microjets written by Jae Jeen Choi and published by . This book was released on 2003 with total page 156 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Advances in Mechanics: Theoretical, Computational and Interdisciplinary Issues by : Michal Kleiber
Download or read book Advances in Mechanics: Theoretical, Computational and Interdisciplinary Issues written by Michal Kleiber and published by CRC Press. This book was released on 2016-05-05 with total page 650 pages. Available in PDF, EPUB and Kindle. Book excerpt: Advances in Mechanics: Theoretical, Computational and Interdisciplinary Issues covers the domain of theoretical, experimental and computational mechanics as well as interdisciplinary issues, such as industrial applications. Special attention is paid to the theoretical background and practical applications of computational mechanics.This volume
Book Synopsis Active Noise Control in Supersonic Impinging Jets Using Pulsed Microjets by : Jae Jeen Choi
Download or read book Active Noise Control in Supersonic Impinging Jets Using Pulsed Microjets written by Jae Jeen Choi and published by . This book was released on 2006 with total page 110 pages. Available in PDF, EPUB and Kindle. Book excerpt: (Cont.) It was observed that the pulsed microjet was able to bring about the same noise reduction as steady injection using approximately 40% of the corresponding mass flow rate of the steady microjet case. Moreover, as the duty cycle increased, the performance of pulsed injection was further enhanced and was observed to completely eliminate the impinging tones at all operating conditions. In order to obtain an optimal performance of the actuator, a new model of the impinging jet flow field is suggested based on a collision model of two identical vortices. In addition to the colliding vortex model, a two-mode feedback model that captures both the low and high-frequency Rossiter mode was suggested to investigate the role of pulsed microjet in the feedback loop. Due to the fact that a low frequency pulsing (16.4 Hz) brought about additional reduction compared to high frequency pulsing, the presence of low frequency mode is identified. In the context of the analytic model, the effect of pulsing is modeled using a input-shaping controller that accomplishes noise-reduction through a suitable redistribution of the acoustic excitation over the high and low frequencies.
