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Experimental Investigation Of The Noise Reduction Of Supersonic Exhaust Jets With Fluidic Inserts
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Book Synopsis Experimental Investigation of the Noise Reduction of Supersonic Exhaust Jets with Fluidic Inserts by : Russell Powers
Download or read book Experimental Investigation of the Noise Reduction of Supersonic Exhaust Jets with Fluidic Inserts written by Russell Powers and published by . This book was released on 2015 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The noise produced by the supersonic, high temperature jets that exhaust from military aircraft is becoming a hazard to naval personnel and a disturbance to communities near military bases. Methods to reduce the noise produced from these jets in a practical full-scale environment are difficult. The development and analysis of distributed nozzle blowing for the reduction of radiated noise from supersonic jets is described. Model scale experiments of jets that simulate the exhaust jets from typical low-bypass ratio military jet aircraft engines during takeoff are performed. Fluidic inserts are created that use distributed blowing in the divergent section of the nozzle to simulate mechanical, hardwall corrugations, while having the advantage of being an active control method. This research focuses on model scale experiments to better understand the fluidic insert noise reduction method. Distributed blowing within the divergent section of the military-style convergent divergent nozzle alters the shock structure of the jet in addition to creating streamwise vorticity for the reduction of mixing noise. Enhancements to the fluidic insert design have been performed along with experiments over a large number of injection parameters and core jet conditions. Primarily military-style round nozzles have been used, with preliminary measurements of hardwall corrugations and fluidic inserts in rectangular nozzle geometries also performed. It has been shown that the noise reduction of the fluidic inserts is most heavily dependent upon the momentum flux ratio between the injector and core jet. Maximum reductions of approximately 5.5 dB OASPL have been observed with practical mass flow rates and injection pressures. The first measurements with fluidic inserts in the presence of a forward flight stream have been performed. Optimal noise reduction occurs at similar injector parameters in the presence of forward flight. Fluidic inserts in the presence of a forward flight stream were observed to reduce the peak mixing noise below the already reduced levels by nearly 4 dB OASPL and the broadband shock-associated noise by nearly 3 dB OASPL. Unsteady velocity measurements are used to complement acoustic results of jets with fluidic inserts. Measured axial turbulence intensities and mean axial velocity are examined to illuminate the differences in the flow field from jets with fluidic inserts. Comparisons of laser Doppler measurements with RANS CFD simulations are shown with good agreement. Analysis of the effect of spatial turbulence on the measured quantities is performed. Experimental model scale measurements of jets with and without fluidic inserts over a simulated carrier deck are presented. The model carrier environment consists of a ground plane of adjustable distance below the jet, and a simulated jet blast deflector similar to those found in practice. Measurements are performed with far-field microphones, near-field microphones, and unsteady pressure sensors. The constructive and destructive interference that results from the interaction of the direct and reflected sound waves is observed and compared with results from free jets. The noise reduction of fluidic inserts in a realistic carrier deck environment with steering of the ``quiet planes'' is examined. The overall sound pressure level in heat-simulated jets is reduced by 3-5 dB depending on the specific angle and ground plane height. Jets impinging upon a modeled jet blast deflector are tested in addition to jets solely in the presence of the carrier deck. Observed modifications to the acoustic field from the presence of the jet blast deflector include downstream acoustic shielding and low frequency augmentation. The region of maximum noise radiation for heat-simulated jets from nozzles with fluidic inserts impinging on the jet blast deflector is reduced in overall sound pressure level by 4-7 dB. This region includes areas where aircraft carrier personnel are located.
Book Synopsis Simulation of Supersonic Jet Noise Reduction Using Fluid Inserts for Low Bypass Ratio Turbofans by : Chitrarth Prasad
Download or read book Simulation of Supersonic Jet Noise Reduction Using Fluid Inserts for Low Bypass Ratio Turbofans written by Chitrarth Prasad and published by . This book was released on 2019 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The design constraints on jet engines for high performance supersonic military aircraft require lower bypass ratios and supersonic exhaust velocities, which result in very high noise levels. This is a great concern to the US Navy as the noise generated from the jet exhaust of high performance supersonic military aircraft can affect the hearing and performance of personnel working in close proximity of the aircraft. There have been reports about the US Department of Veteran Affairs spending over hundreds of millions of dollars in disability payments for hearing loss compensation to former Navy personnel. In addition to this, jet noise is also a source of annoyance in communities in the vicinity of airbases and military training routes.Over the years, several noise reduction methods have been proposed with varying levels of success. The most effective noise reduction strategies include the installation of chevrons, and the use of corrugated seals, among many others. One primary disadvantage of these technologies is that they are passive technologies and cannot be switched off or modified after take-off and hence may reduce overall aircraft performance. An active, though steady, noise reduction technology is the use of fluid inserts in the divergent section of a converging-diverging nozzle. The fluid inserts consist of rows of injectors that inject a small amount of bypass air into the diverging section of the nozzle. It has been shown that by altering the configuration and operating conditions of the fluid inserts, noise reduction for both mixing and shock noise can be achieved. Since this blowing can be controlled, the fluid inserts can be switched off or modified after take-off to minimize any performance penalty to the aircraft.Although considerable experimental research has been performed to explore the effects of fluid inserts on the jet exhaust, the available data have been found to be insufficient to correlate the noise reduction with changes in the flow-field due to the noise reduction device. The present study is an extension to the previousresearch on fluid inserts that uses Large Eddy Simulation (LES) with the Ffowcs Williams-Hawkings (FWH) analogy for farfield noise prediction. The simulations are carried out using a commercially available CFD package, STAR-CCM+. The project aims to simulate and analyze the unsteady flow changes associated withthe noise reduction device to help understand the detailed mechanisms for the observed noise reductions.Different fluid insert configurations are used to analyze the effect of individual injector placement in a fluid insert on noise generation. It is observed that the changes in upstream noise correlate extremely well with the shock structure of the fluid insert jets downstream of the nozzle exit. Further insight into the noisereduction patterns is obtained by using two-point space time correlations and the use of the modal techniques such as Proper Orthogonal Decomposition on the near-field data on the FWH surface, which show that fluid inserts reduce the amplitude of the noise radiating coherent structures. Using Doaks Momentum Potential Theory, it is observed that the changes associated with fluid insertson the hydrodynamic and acoustic modes correlate well with the far-field noise reduction.
Book Synopsis Simulations of the Flow Generated by Fluidic Inserts for Supersonic Jet Noise Reduction Based on Steady RANS Simulations by : Matthew Kapusta
Download or read book Simulations of the Flow Generated by Fluidic Inserts for Supersonic Jet Noise Reduction Based on Steady RANS Simulations written by Matthew Kapusta and published by . This book was released on 2015 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The investigation of military jet noise prediction and reduction is an ongoing activity. Supersonic military jets radiate higher noise levels than commercial aircraft and are not subject to noise requirements. The noise generating mechanisms for high-speed jets are not entirely understood, making it difficult to set strict noise standards similar to those imposed for commercial aircraft. However, many noise reduction techniques have been applied to attempt to alleviate environmental and health concerns. Little success has been achieved to date for noise reduction of exhaust jets on supersonic tactical aircraft.A newly developed method involves a system that generates fluidic inserts in a supersonic nozzle flow to produce noise reduction. Numerical simulations have been performed for a military-style basline nozzle and with the noise reduction method of fluidic inserts used at a design Mach number of 1.65 and at various off design conditions. The purpose of the current numerical study is to provide insight for the flow field generated by the fluidic inserts used to reduce supersonic jet noise. The supersonic jet simulations are based on the use of high fidelity meshes combined with advanced CFD technology. Steady Reynolds-averaged Navier-Stokes (RANS) simulations are used to predict the flow field. Noise measurements have been performed experimentally and the results from the numerical simulations provide a correlation between aerodynamic properties and the corresponding noise reduction. The complex nozzle geometry is modeled using both an unstructured mesh and a multiblock structured mesh. The grids are generated by ANSYS ICEM and Gridgen respectively. The numerical simulations are performed using ANSYS CFX and Wind-US. The simulations with Wind-US use the Spalart-Allmaras turbulence model, while the simulations with ANSYS CFX use the Menter SST turbulence model. The results from the two flow solvers are compared and provide good agreement. The objective is to simulate a military-style nozzle, which resembles engines of the GE F404 family, with fluidic inserts. The purpose of the fluidic inserts is to alter the flow field similar to that of a hard wall corrugation in order to reduce components of noise radiation. The addition of the fluidic inserts increases the complexity of the flow field for the supersonic jet. The numerical simulations performed help to better distinguish the effects on the flow field due to the fluidic inserts. Preliminary work has been performed on a simpler geometry to provide further insight to the effect of the fluidic inserts on the supersonic jet flow field. These simulations are performed by fluid injection into a supersonic freestream over a flat plate. All numerical simulations used a freestream Mach number of 1.5. The numerical simulations used a wide range of pressure ratios for injecting the fluid into the supersonic freestream. By changing the pressure ratio of the fluid injection, the deflection of the freestream flow was better understood. Simulations on a full three dimensional nozzle with fluidic inserts were performed with conditions based on the preliminary studies. Parameters such as total pressure and total temperature provide a representation of the fluidic insert shape. Other integrated flow properties at the nozzle exit such as streamwise vorticity and pressure differential were used to correlate with the noise reduction seen in the experiments.
Book Synopsis Supersonic Jet Exhaust Noise Investigation by : Paul R. Knott
Download or read book Supersonic Jet Exhaust Noise Investigation written by Paul R. Knott and published by . This book was released on 1974 with total page 282 pages. Available in PDF, EPUB and Kindle. Book excerpt: This progress report summarizes the major theoretical and experimental efforts performed during the first year of a two-year program sponsored by the Air Force and the Department of Transportation on Supersonic Jet Exhaust Noise. The overall objective of the program is to develop the technology to significantly reduce supersonic aircraft propulsion system noise with minimum associated performance and weight penalties. To reach the objectives of this program a varied and comprehensive research program is being carried out to develop the basic theory and experimental methods for understanding and quantizing the acoustic characteristics of simple supersonic jets for a range of velocities and temperatures typical of present and future military and commercial supersonic aircraft propulsion systems. (Modified author abstract).
Book Synopsis Flinovia—Flow Induced Noise and Vibration Issues and Aspects-II by : Elena Ciappi
Download or read book Flinovia—Flow Induced Noise and Vibration Issues and Aspects-II written by Elena Ciappi and published by Springer. This book was released on 2018-05-25 with total page 365 pages. Available in PDF, EPUB and Kindle. Book excerpt: This is the proceedings of the Second International Workshop on Flow Induced Noise and Vibration (FLINOVIA), which was held in Penn State, USA, in April 2016. The authors’ backgrounds represent a mix of academia, government, and industry, and several papers include applications to important problems for underwater vehicles, aerospace structures and commercial transportation. The book offers a valuable reference guide for all those working in the area of flow-induced vibration and noise. Flow induced vibration and noise (FIVN) remains a critical research topic. Even after over 50 years of intensive research, accurate and cost-effective FIVN simulation and measurement techniques remain elusive. This book gathers the latest research from some of the most prominent experts in the field. The book describes methods for characterizing wall pressure fluctuations, including subsonic and supersonic turbulent boundary layer flows over smooth and rough surfaces using computational methods like Large Eddy Simulation; for inferring wall pressure fluctuations using inverse techniques based on panel vibrations or holographic pressure sensor arrays; for calculating the resulting structural vibrations and radiated sound using traditional finite element methods, as well as advanced methods like Energy Finite Elements; for using scaling approaches to universally collapse flow-excited vibration and noise spectra; and for computing time histories of structural response, including alternating stresses.
Book Synopsis Azimuthally Varying Noise Reduction Techniques Applied to Supersonic Jets by : Nicholas S. Heeb
Download or read book Azimuthally Varying Noise Reduction Techniques Applied to Supersonic Jets written by Nicholas S. Heeb and published by . This book was released on 2015 with total page 258 pages. Available in PDF, EPUB and Kindle. Book excerpt: An experimental investigation into the effect of azimuthal variance of chevrons and fluidically enhanced chevrons applied to supersonic jets is presented. Flow field measurements of streamwise and cross-stream particle imaging velocimetry were employed to determine the causes of noise reduction, which was demonstrated through acoustic measurements. Results were obtained in the over- and under- expanded regimes, and at the design condition, though emphasis was placed on the overexpanded regime due to practical application. Surveys of chevron geometry, number, and arrangement were undertaken in an effort to reduce noise and/or incurred performance penalties. Penetration was found to be positively correlated with noise reduction in the overexpanded regime, and negatively correlated in underexpanded operation due to increased effective penetration and high frequency penalty, respectively. The effect of arrangement indicated the beveled configuration achieved optimal abatement in the ideally and underexpanded regimes due to superior BSAN reduction. The symmetric configuration achieved optimal overexpanded noise reduction due to LSS suppression from improved vortex persistence. Increases in chevron number generally improved reduction of all noise components for lower penetration configurations. Higher penetration configurations reached levels of saturation in the four chevron range, with the potential to introduce secondary shock structures and generate additional noise with higher number. Alternation of penetration generated limited benefit, with slight reduction of the high frequency penalty caused by increased shock spacing. The combination of alternating penetration with beveled and clustered configurations achieved comparable noise reduction to the standard counterparts. Analysis of the entire data set indicated initial improvements with projected area that saturated after a given level and either plateaued or degraded with additional increases. Optimal reductions were 3-7dB depending on operating condition and observation angle. The fluidic enhancement of the low penetration chevrons indicated significant improvement in the overexpanded regime, with detrimental effect at higher conditions. Improvements were generally due to shock noise and turbulent mixing noise reductions caused by decreased shock strength and LSS growth inhibition. Investigation of azimuthal configurations indicated further improvements were achieved by the clustered configuration due to additional BSAN reductions caused by drastic modification of the shock cell structure due to elliptification of the jet cross section.
Book Synopsis Supersonic Jet Exhaust Noise Investigation. Volume I. Summary Report by : Paul R. Knott
Download or read book Supersonic Jet Exhaust Noise Investigation. Volume I. Summary Report written by Paul R. Knott and published by . This book was released on 1976 with total page 137 pages. Available in PDF, EPUB and Kindle. Book excerpt: This report summarizes major theoretical aerodynamic and acoustic developments and experimental findings aimed at providing a better understanding and a detailed mathematical specification of the noise-producing sources of simple exhaust jets. A review is given of calculation procedures for shock wave structure and flow field properties of simple circular jets. Results of new theoretical acoustic developments illustrating the influence of a jet's mean flow shrouding on jet acoustic radiation for unheated and heated jets are outlined. Additional discussions of interesting insights regarding the classical turbulent mixing theory of jet noise and the aeroacoustic formulations for a jet's orderly structure are given. Summaries of a series of high velocity, high temperature velocity field measurements using a General Electric developed laser velocimeter are discussed, and the application of the velocimeter for performing turbulence spectra and in-jet to far-field cross-correlation type measurements is reviewed. Key experiments illustrating the influence of swirl and combustion roughness on jet noise generation/reduction are presented. Results of high velocity and high temperature refraction experiments are also discussed, as well as discussions concerning jet flow amplifying effects of injected low frequency noise. Additionally, suggestions concerning shock-related noise as related to full-size engines are given. And finally, recommendations for future investigations are given. (Author).
Book Synopsis An Analysis of Noise Reduction in Supersonic Jets by Fluid Insert Nozzles by : Venkata Rajeshwar Majety
Download or read book An Analysis of Noise Reduction in Supersonic Jets by Fluid Insert Nozzles written by Venkata Rajeshwar Majety and published by . This book was released on 2018 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The primary objective of this research is to analyze the noise reduction obtained with the use of fluid insert nozzles in heated supersonic jets. In this regard, the far-field pressure data of two types of nozzles (baseline and fluid inserts) are used to investigate and validate the spatiotemporal characteristics of the radiation field, and to determine the sound reduction obtained. Further, to gain a better understanding of the noise radiated, the polar correlation technique is used to determine the location and relative strengths of the noise sources. The results of this research can be summarized as follows: the fluid insert nozzles reduce the overall sound radiated by a maximum amount of 10 dB and 4 dB respectively in the downstream and upstream directions of the jet flow. The highest levels of sound are radiated in the downstream directions of the jet flow for all the nozzle cases. The greatest amount of noise reduction is obtained in the 60 azimuthal plane. Irrespective of the nozzle type, significant noise source strength is located within ten nozzle diameters downstream from the nozzle exit. As the frequency increases, the highest peak of the noise source strength distribution moves closer to the nozzle exit.
Book Synopsis Supersonic Jet Exhaust Noise Investigation. Volume II. Technical Report by : Paul R. Knott
Download or read book Supersonic Jet Exhaust Noise Investigation. Volume II. Technical Report written by Paul R. Knott and published by . This book was released on 1976 with total page 396 pages. Available in PDF, EPUB and Kindle. Book excerpt: This report discusses detailed accounts of major theoretical and experimental investigations directed toward obtaining better understanding and mathematical specification of supersonic turbulent jets. Complete theoretical discussions are given describing the influence of a jet's mean flow shrouding on acoustic radiation of heated and unheated jets, approximate closed form acoustic expressions for turbulent mixing noise characterized by self-noise and shear-noise are given, and theoretical aero-acoustic formulations for the orderly structure of supersonic jets are reviewed. Extensive theory/data comparisons of developed acoustic models are given. Experimental investigations aimed at studying high velocity jet refraction, and the influence of jet swirl and upstream combustion roughness on jet noise is presented. Additionally, an extensive series of laser velocimeter measurements for high velocity and high temperature simple circular jets is discussed. Results include hot-film/laser velocimeter comparisons for ambient jets, mean velocity and turbulent velocity plume surveys of heated supersonic shock-free and shocked flow nozzles, and a demonstration experiment illustrating the capability of performing in-jet turbulence to far-field acoustic cross-correlation. (Author).
Book Synopsis Fundamental Study of Jet Noise Generation and Suppression by : W. C. Sperry
Download or read book Fundamental Study of Jet Noise Generation and Suppression written by W. C. Sperry and published by . This book was released on 1961 with total page 150 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Experimental Study of Exhaust System Mixers for a Subsonic Jet Noise Reduction by : Hyoun-Woo Shin
Download or read book Experimental Study of Exhaust System Mixers for a Subsonic Jet Noise Reduction written by Hyoun-Woo Shin and published by . This book was released on 1996 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Pressure Measurements in a Supersonic Jet with Fluid Inserts by : James Falcone
Download or read book Pressure Measurements in a Supersonic Jet with Fluid Inserts written by James Falcone and published by . This book was released on 2018 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Extremely high levels of noise, capable of damaging the human ear, are emitted from theexhaust leaving military grade aircraft engines. Military personnel, specifically those on the decksof aircraft carriers, are regularly exposed to this dangerous noise and as a result often sustainpermanent hearing damage. A novel approach to reducing the noise levels experienced by thesepersonnel is through the use of fluid inserts in the diverging section of an aircraft engines nozzle.These fluid inserts blow additional air into the exhaust flow which has been shown to effectivelyreduce noise. This study sought to further the understanding of the flow physics by which thefluid inserts can reduce noise. Pressure surveys of a scaled GE 404 class engine nozzle werecompleted with and without the use of fluid inserts. The alterations created by the fluid inserts inthe downstream flow are visualized and discussed. The experimental results are also compared toRANS CFD simulations of jets from the same nozzle and operating conditions to further evaluatethe computations and improve future simulations.Throughout the duration of the experiments, jet asymmetries were also carefully explored forthe baseline jet as well as the fluid insert jet. Asymmetries within a jet can have an impact onnoise reduction by unknowingly redistributing the flow in undesirable ways. The reasons for theseasymmetries are proposed.
Book Synopsis High Velocity Jet Noise Source Location and Reduction. Task 3 - Experimental Investigation of Suppression Principles. Volume II - Parametric Testing and Source Measurements by :
Download or read book High Velocity Jet Noise Source Location and Reduction. Task 3 - Experimental Investigation of Suppression Principles. Volume II - Parametric Testing and Source Measurements written by and published by . This book was released on 1978 with total page 870 pages. Available in PDF, EPUB and Kindle. Book excerpt: Experimental investigations were conducted of suppression principles, including developing an experimental data base, developing a better understanding of jet noise suppression principles, and formulating empirical methods for the acoustic design of jet noise suppressors. Acoustic scaling has been experimentally demonstrated, and five 'optimum' nozzles have been selected for subsequent anechoic free-jet testing. A series of experimental tests was conducted to provide farfield acoustic data on 47 baseline and suppressor nozzle configurations and to provide aerodynamic nozzle performance on 18 of the configurations. Suppressor design parameters evaluated experimentally included: suppressor area ratio, radius ratio, flow management, inner stream geometry, element number and type, treated ejectors on multielement and unsuppressed inverted-coannualar-flow nozzles. Parametric testing established suppression levels for single and dual flow nozzles during static operation. Selective free- jet tests conducted on eight configurations were utilized to establish flight suppression levels for plug, chute, tube and hole nozzles. The aerodynamic performance test program illustrated that suppressed exhaust nozzles which incorporate elemental base areas as an integral part of the design are sensitive to external Mach number. In general suppressor element base drag was the most significant loss mechanism. This volume is part of the four volume set that constitutes the Task 3 final report.
Book Synopsis Experimental Investigation of Noise from Interacting Axisymmetric Supersonic Jet Flows by : James Chun-Ying Yu
Download or read book Experimental Investigation of Noise from Interacting Axisymmetric Supersonic Jet Flows written by James Chun-Ying Yu and published by . This book was released on 1968 with total page 156 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Jet Noise Reduction Potential from Emerging Variable Cycle Technologies by : Brenda Henderson
Download or read book Jet Noise Reduction Potential from Emerging Variable Cycle Technologies written by Brenda Henderson and published by BiblioGov. This book was released on 2013-06 with total page 26 pages. Available in PDF, EPUB and Kindle. Book excerpt: Acoustic and flow-field experiments were conducted on exhaust concepts for the next generation supersonic, commercial aircraft. The concepts were developed by Lockheed Martin (LM), Rolls-Royce Liberty Works (RRLW), and General Electric Global Research (GEGR) as part of an N+2 (next generation forward) aircraft system study initiated by the Supersonics Project in NASA s Fundamental Aeronautics Program. The experiments were conducted in the Aero-Acoustic Propulsion Laboratory at the NASA Glenn Research Center. The exhaust concepts utilized ejectors, inverted velocity profiles, and fluidic shields. One of the ejector concepts was found to produce stagnant flow within the ejector and the other ejector concept produced discrete-frequency tones that degraded the acoustic performance of the model. The concept incorporating an inverted velocity profile and fluid shield produced overall-sound-pressure-level reductions of 6 dB relative to a single stream nozzle at the peak jet noise angle for some nozzle pressure ratios. Flow separations in the nozzle degraded the acoustic performance of the inverted velocity profile model at low nozzle pressure ratios.
Book Synopsis The Generation and Radiation of Supersonic Jet Noise. Volume V. An Experimental Investigation of Jet Noise Variation with Velocity and Temperature by : Peter A. Lush
Download or read book The Generation and Radiation of Supersonic Jet Noise. Volume V. An Experimental Investigation of Jet Noise Variation with Velocity and Temperature written by Peter A. Lush and published by . This book was released on 1972 with total page 172 pages. Available in PDF, EPUB and Kindle. Book excerpt: A series of experiments was conducted for the purpose of clearly isolating and quantifying the noise sources associated with supersonic jet noise and for establishing the effect of refraction on the radiated field of these sources, as well as the radiation field characteristics of these sources. Results from the turbulent-mixing tests and the shock-associated tests are appended to this report in separate volumes. The turbulence noise 1/3 octave corrected data appear in Appendix I and the shock-associated narrow-band spectra appear in Appendix 2. (Author).
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.
