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Mixing Control In Supersonic Rectangular Jets Using Plasma Actuators
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Book Synopsis Mixing Control in Supersonic Rectangular Jets Using Plasma Actuators by : Robert M. Snyder
Download or read book Mixing Control in Supersonic Rectangular Jets Using Plasma Actuators written by Robert M. Snyder and published by . This book was released on 2007 with total page 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 (LAFPA) 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. These actuators were implemented on a rectangular nozzle in order to optimize the efficiency of mixing enhancement between the jet and the ambient air. Actuators were tested for a Mach 2.0 flow over a wide range of forcing frequencies and the effects were evaluated using flow visualization techniques. Results show the effects of forcing frequency and other parameters on the development of large-scale structures within the flow. Flow visualization testing over a broad range of forcing frequencies and duty cycles revealed the presence of large coherent structures and thus most favorable mixing enhancement in the 6-8 kHz (StF = 0.15-0.2) range. The m = " 1 (flapping) mode produced a clear pattern of alternating structures within the aforementioned frequency band. It was also observed that the effect of varying duty cycle within this frequency range has little effect on the control authority.
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 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 Understanding and Control of Coupling of Supersonic Twin Jets Using Localized Arc Filament Plasma Actuators by : Jordan D. Cluts
Download or read book Understanding and Control of Coupling of Supersonic Twin Jets Using Localized Arc Filament Plasma Actuators written by Jordan D. Cluts and published by . This book was released on 2018 with total page 110 pages. Available in PDF, EPUB and Kindle. Book excerpt: A twin-jet consists of two jet engines that are close enough to one another on an aircraft for the plumes to interact and merge downstream of the nozzle exit. This interaction can cause the noise generated by twin jets to be louder than an equivalent single jet under certain operating conditions. The noise of all jets is a health concern for communities near airports and personnel on aircraft carrier decks, but twin jets are of particular concern due to their increased noise levels. Additionally, the coupling of twin jets can cause strong near field pressure fluctuations that have the potential to damage airframes of military aircraft through sonic fatigue as occurred on both the F-15 and the B-1A during their development. Previous research into twin jets has studied a variety of twin-jet nozzle configurations. This study focuses on round converging-diverging nozzles with a center-to-center spacing of 2.0 nozzle diameters---close to that found in military aircraft. Localized arc filament plasma actuators (LAFPAs) are perturbation-based flow control devices that excite jet instabilities with small energy input and alter their characteristics. They have been used to control the noise generated by single jets. These actuators can alter the dominant mode (the shape of the large-scale turbulent structures) present in the jet plume by creating small thermal perturbations near the nozzle exit. LAFPAs were applied to test their efficacy at altering the dominant mode and as a diagnostic tool to study the behavior of the different modes in the twin-jet. Regardless of the naturally dominant mode in the twin-jet at a given operating condition, the LAFPAs can change the mode present to match the excited mode. This includes eliminating the strong coupling at modes and conditions where it normally occurs. Far field and near field acoustic measurements show that when the flapping mode is dominant in the twin-jet, the resulting coupling causes higher noise and near field pressure fluctuations than other modes. Axisymmetric and helical modes synchronize the large-scale turbulent structures so that they are generated simultaneously, but do not amplify one another to create the higher noise and pressure fluctuations of the flapping mode. The identities of these modes were confirmed using phase-averaged schlieren imaging which reveals the shape of the different modes in the twin-jet, both naturally occurring and excited using LAFPAs Both schlieren images and screech tone frequencies were captured for a twin-jet at elevated temperatures. These images revealed that the flapping mode disappears in the twin-jet as the temperature increases and is replaced by the helical mode. A theoretical model in the literature designed to predict the screech tone frequency in single jets was applied to the twin-jet. This model accurately predicted the tones present in the twin-jet and was able to predict a shift from one frequency to another when a mode shifts from the flapping mode to the helical mode due to increased jet temperature. The screech tones of the twin-jet closely match the feedback loop of the single jet.
Book Synopsis Advances in Heat Transfer and Fluid Dynamics by : Mohammad Altamush Siddiqui
Download or read book Advances in Heat Transfer and Fluid Dynamics written by Mohammad Altamush Siddiqui and published by Springer Nature. This book was released on with total page 425 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Flow Control written by Thomas C. Corke and published by Cambridge University Press. This book was released on 2024-04-11 with total page 482 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book provides a comprehensive treatment of passive and active flow control in fluid dynamics, with an emphasis on utilizing fluid instabilities for enhancing control performance. Examples are given from a wide range of technologically important flow fields occurring in aerospace applications, from low-subsonic to hypersonic Mach numbers. This essential book can be used for both research and teaching on the topics of fluid instabilities, fluid measurement and flow actuator techniques, and problem sets are provided at the end of each chapter to reinforce key concepts and further extend readers' understanding of the field. The solutions manual is available as a online resource for instructors. The text is well suited for both graduate students in fluid dynamics and for practising engineers in the aerodynamics design field.
Book Synopsis Noise Mitigation of a Jet Using Localized Arc Filament Plasma Actuators by : Casey B. Hahn
Download or read book Noise Mitigation of a Jet Using Localized Arc Filament Plasma Actuators written by Casey B. Hahn and published by . This book was released on 2010 with total page 44 pages. Available in PDF, EPUB and Kindle. Book excerpt: Abstract: Localized arc filament plasma actuators (LAFPAs) are used at The Gas Dynamics and Turbulence Laboratory (GDTL) for the purpose of controlling the downstream development of a 1-inch exit diameter jet. The lab has the capability to study both subsonic and supersonic jets with a primary goal being the mitigation of noise emitted by a jet. However, the mechanism by which the actuators are capable of perturbing the instabilities of the jet is unclear. It has been proposed that the ring groove, initially added to shield the plasma arcs from the high-speed jet flow, of the nozzle extension that houses the actuators is crucial for effective actuation. To study this possibility a new nozzle extension, which relocates the electrodes to the nozzle extension face and deletes the ring groove, is used. A comparison of the acoustic results of a traditional extension with a ring groove and the new nozzle extension without the ring groove is used to determine the effect of the ring groove. The results show that the same general trends and levels of noise attenuation and amplification are achieved with either extension. Thus, it is concluded that the ring groove is not essential for effective actuation.
Book Synopsis Resonant Interaction of a Linear Array of Supersonic Rectangular Jets: An Experimental Study by : Ganesh Raman
Download or read book Resonant Interaction of a Linear Array of Supersonic Rectangular Jets: An Experimental Study written by Ganesh Raman and published by . This book was released on 1994 with total page 28 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Experimental Investigation of the Effect of Swirl on Mixing Enhancement of Supersonic Rectangular Jets by : Jason E. Frank
Download or read book Experimental Investigation of the Effect of Swirl on Mixing Enhancement of Supersonic Rectangular Jets written by Jason E. Frank and published by . This book was released on 1994 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Enhanced Mixing of Multiple Supersonic Rectangular Jets by Synchronized Screech by : R. Taghavi
Download or read book Enhanced Mixing of Multiple Supersonic Rectangular Jets by Synchronized Screech written by R. Taghavi and published by . This book was released on 1994 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis A Study of Rectangular Supersonic Jets Modified for Mixing Enhancement and Noise Reduction (AASERT97). by :
Download or read book A Study of Rectangular Supersonic Jets Modified for Mixing Enhancement and Noise Reduction (AASERT97). written by and published by . This book was released on 2001 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: This report presents the results of two experimental activities. Part I involves passive control of mixing and noise in a rectangular supersonic jet. Part II involves development and characterization of high amplitude and high bandwidth actuators for use in active control of high Reynolds and Mach numbers flows such as the jet in Part I. Nozzle trailing edge modifications were used in part I, which substantially enhanced mixing and reduced noise radiation in non-ideally expanded conditions, but did not significantly alter the mixing or noise for the ideally expanded flow condition. In part II, an in depth investigation of the Hartmann Tube was carried out. The effects of tube depth, separation distance between the tube and the nozzle, and the jet Mach number were explored. Experiments were also performed on a Hartmann Tube based Fluidic Actuator. Striking similarities were observed in the frequency content and amplitude of tonal frequencies in the global near-field pressure and far-field acoustic measurements, as well as, the flow results. Time traces of pressure in the tube were used to explain the major differences between the primary frequency of HT and the quarter-wave frequency. Flow visualization results showed a pulsating flow very rich in vortical structures.
Book Synopsis An Experimental Study of Mixing and Noise in a Supersonic Rectangular Jet with Modified Trailing Edges by : Jin-Hwa Kim
Download or read book An Experimental Study of Mixing and Noise in a Supersonic Rectangular Jet with Modified Trailing Edges written by Jin-Hwa Kim and published by . This book was released on 1998 with total page 408 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis The Proceedings of 2023 4th International Symposium on Insulation and Discharge Computation for Power Equipment (IDCOMPU2023) by : Xuzhu Dong
Download or read book The Proceedings of 2023 4th International Symposium on Insulation and Discharge Computation for Power Equipment (IDCOMPU2023) written by Xuzhu Dong and published by Springer Nature. This book was released on 2024-03-28 with total page 731 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book includes original, peer-reviewed research papers from the 2023 4th International Symposium on Insulation and Discharge Computation for Power Equipment (IDCOMPU2023), held in Wuhan, China. The topics covered include but are not limited to: insulation, discharge computations, electric power equipment, and electrical materials. The papers share the latest findings in the field of insulation and discharge computations of electric power equipment, making the book a valuable asset for researchers, engineers, university students, etc.
Book Synopsis Simulation of the Localized Arc Filament Plasma Actuators for Jet Excitation by : Clifford A. Brown
Download or read book Simulation of the Localized Arc Filament Plasma Actuators for Jet Excitation written by Clifford A. Brown and published by . This book was released on 2010 with total page 201 pages. Available in PDF, EPUB and Kindle. Book excerpt: "The concept of jet control by external forcing is not new. The first published demonstration of a jet responding to outside forces occurred in the mid-1800's. It was not, however, until the 1950's, with the advent of commercial jet aircraft, that scientific study of the subject greatly increased as researchers used external forcing to study the structure and noise sources present in a jet plume. Interest in active jet control continues today, particularly with the additional possibilities afforded by significant advances in measurement and simulation technology, even though it remains limited by the available jet actuators to relatively small, low Reynolds number jets that are of little similarity to the large, highly turbulent jets common in real world applications. However, the recently developed Localized Arc Filament Plasma Actuators (LAFPA) have the potential to expand active jet control research to include these larger, higher Reynolds number jets. The LAFPA have been used successfully to control a small-diameter, high-speed turbulent jet to achieve some plume mixing enhancement and limited noise mitigation. The system, however, must still be extended to a larger class of jets common in the real world and optimized for an application. This work addresses both of these issues. First, experiments are conducted to determine the impact of the LAFPA on a large-scale jet. A model of the LAFPA is then developed for use in the future CFD based studies of excited jets. The model performance is investigated using multiple CFD methodologies to determine the optimal combination of actuator model and CFD scheme for excited jet simulations. Ultimately, the model developed will be used by researchers in future simulations to optimize the actuator system for noise reduction, IR signature reduction, or to system scalability for deployment on larger jets in real-world applications."--Abstract.
Book Synopsis Fundamental Physics and Application of Plasma Actuators for High-speed Flows by : Eli S. Lazar
Download or read book Fundamental Physics and Application of Plasma Actuators for High-speed Flows written by Eli S. Lazar and published by . This book was released on 2011 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: In this dissertation, a detailed investigation is given discussing three plasma-based flow control methods. These methods included plasma generated by laser energy, microwaves, and electric arc. The plasma generated by laser energy was also applied to a sonic transverse jet in a supersonic cross flow. Lastly, the particle image velocimetry diagnostic was considered and a technique developed to evaluate measurement uncertainty and using experimental velocity data to solve for density from the continuity equation. In the laser-spark system, the effect of ambient pressure in the range of 0.1 to 1.0 atm and wavelength (266 nm and 532 nm) on the size, temperature, electron number density, and fraction of laser energy absorbed in a laser-induced plasma in air has been conducted. The plasma was generated by using optics to focus the laser energy. The focused laser pulse resulted in the induced optical breakdown of air, creating a plasma to perturb the flow field. As pressure or wavelength are reduced, the size of the plasma, its electron number density, and the fraction of incident laser energy that is absorbed are all found to decrease significantly. For the plasma generated by microwaves, the feasibility of using the system for flow control was demonstrated at pressures ranging from 0.05 atm to 1 atm and for pulsing frequencies between 400 Hz to 10 kHz. The setup was based on a quarter-wave coaxial resonator being operated with a microwave frequency of 2.45 GHz. Analysis of reflected power measurements suggested that the microwave energy could be best coupled into the resonator by using a small inductive loop, where the geometry can be experimentally optimized. The plasma was first characterized by recording images of the emission and taking temporal emission waveform profiles. Tests were conducted in quiescent air and analyzed with schlieren photography to determine the effectiveness of a plasma pulse to produce an instantaneous flow perturbation. Examination of phase averaged schlieren images revealed that a blast was produced by the emission and could be used to alter a flow field. The emission was also thermally characterized through emission spectroscopy measurements where the vibrational and rotational temperatures of the plasma were determined. The last system considered was a localized arc filament plasma actuator, or LAFPA-type device. The system creates electric arcs by generating electric fields in the range of 20 kV/cm between two pin-type electrodes. The potential of the actuator to influence surrounding quiescent flow was investigated using emission imaging, schlieren imaging, current and voltage probes, particle image velocimetry (PIV), and emission spectroscopy. The schlieren imaging revealed a potential to cause blast 0́−Mach0́+ waves and a synthetic jet with controllable directionality dependent on cavity orientation. The electric measurements revealed that, in order to increase the power discharged by the plasma, the electrode separation will only aid mildly and that an optimum plasma current exists (between 300-400 mA for the tested parameter space). The PIV data were acquired for various actuation frequencies and showed a trend between discharge frequency and maximum induced jet velocity. Finally, the emission spectroscopy data were acquired for four different cases: two electrode separations and two plasma currents. For each of the four conditions tested, the spectrum fit very well to a thermal distribution for early times in the emission. However, at later times in the emission, the spectrum no longer matched that of the second positive system under optically thick conditions for any combination of rotational and vibrational temperatures. Using the plasma generated by laser energy, an experimental investigation of flow control on a sonic underexpanded jet injected normally into a Mach 2.45 crossflow is reported. The jet exit geometry was circular and was operated at a jet-to-crossflow momentum flux ratio of 1.7. The unperturbed flow field was analyzed with schlieren imaging, PIV velocity data, surface oil flow visualizations, and pressure sensitive paint measurements. As a means of excitation to the flow field, the plasma energy was focused in the center of the jet exit at three different vertical locations. The perturbed resulting flow field was analyzed with schlieren photography and particle image velocimetry. Analysis of phase averaged schlieren images suggested that the resulting blast wave from the laser pulse disrupted the structure of the barrel shock and Mach disk. The two-component velocity field data revealed that the excitation pulse also caused a perturbation to the jet shear layer and induced the formation of vortices that convect downstream. Finally, additional techniques were developed for the PIV diagnostics. First, while PIV is an established experimental technique for determining a velocity field, quantifying the uncertainty related with this method remains a challenging task. To this end, four sources of uncertainty are assessed: equipment, particle lag, sampling size, and processing algorithm. An example uncertainty analysis is conducted for a transverse sonic jet injected into a supersonic crossflow. However, the analysis is not specific to the example flow field and may be generally applied to any mean velocity field. Secondly, using the velocity data from PIV, a technique was developed to solve for density from the continuity equation over the entire flow field. The technique is validated using data from CFD simulations and demonstrated for experimental data for two flow fields.
Book Synopsis Enhanced Mixing of a Rectangular Supersonic Jet by Natural and Induced Screech by : Edward J. Rice
Download or read book Enhanced Mixing of a Rectangular Supersonic Jet by Natural and Induced Screech written by Edward J. Rice and published by . This book was released on 1993 with total page 16 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Control of Supersonic Axisymmetric Base Flows Using Passive Splitter Plates and Pulsed Plasma Actuators by :
Download or read book Control of Supersonic Axisymmetric Base Flows Using Passive Splitter Plates and Pulsed Plasma Actuators written by and published by . This book was released on 2013 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
