An Experimental Study Of Jet Exhaust Simulation
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An Experimental Study Of Jet Exhaust Simulation
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Author :
language : en
Publisher:
Release Date : 1974
An Experimental Study Of Jet Exhaust Simulation written by and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 1974 with categories.
Experimental Study Of Jet Exhaust Simulation Parameters
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Author : William Bernard Compton
language : en
Publisher:
Release Date : 1973
Experimental Study Of Jet Exhaust Simulation Parameters written by William Bernard Compton and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 1973 with categories.
Simulation Of Supersonic Jet Noise Reduction Using Fluid Inserts For Low Bypass Ratio Turbofans
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Author : Chitrarth Prasad
language : en
Publisher:
Release Date : 2019
Simulation Of Supersonic Jet Noise Reduction Using Fluid Inserts For Low Bypass Ratio Turbofans written by Chitrarth Prasad and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2019 with categories.
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.
An Experimental Modeling Study Of Jet Attachment During Counterflow Thrust Vectoring
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Author : National Aeronautics and Space Administration (NASA)
language : en
Publisher: Createspace Independent Publishing Platform
Release Date : 2018-07-17
An Experimental Modeling Study Of Jet Attachment During Counterflow Thrust Vectoring written by National Aeronautics and Space Administration (NASA) and has been published by Createspace Independent Publishing Platform this book supported file pdf, txt, epub, kindle and other format this book has been release on 2018-07-17 with categories.
Recent studies have shown the applicability of vectoring rectangular jets using asymmetrically applied counterflow in the presence of a short collar. This novel concept has applications in the aerospace industry where counterflow can be used to vector the thrust of a jet's exhaust, shortening take-off and landing distances and enhancing in-flight maneuverability of the aircraft. Counterflow thrust vectoring, 'CFTV' is desirable due to its fast time response, low thrust loss, and absence of moving parts. However, implementation of a CFTV system is only possible if bistable jet attachment can be prevented. This can be achieved by properly designing the geometry of the collar. An analytical model is developed herein to predict the conditions under which a two-dimensional jet will attach to an offset curved wall. Results from this model are then compared with experiment; for various jet exit Mach numbers, collar offset distances, and radii of curvature. Their excellent correlation permits use of the model as a tool for designing a CFTV system. Strykowski, Paul J. Langley Research Center THRUST VECTOR CONTROL; COUNTERFLOW; MATHEMATICAL MODELS; AIRCRAFT ENGINES; JET FLOW; SHEAR LAYERS; DATA ACQUISITION; MASS FLOW; FREE JETS; AERODYNAMIC DRAG; REATTACHED FLOW; MACH NUMBER; EXPERIMENTATION; DATA CORRELATION...
Nasa Technical Memorandum
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Author :
language : en
Publisher:
Release Date : 1989
Nasa Technical Memorandum written by and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 1989 with Aeronautics categories.
Scientific And Technical Aerospace Reports
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Author :
language : en
Publisher:
Release Date : 1995
Scientific And Technical Aerospace Reports written by and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 1995 with Aeronautics categories.
Numerical Simulation And Experimental Investigation Of Jet Injection Into A Quiescent Combustion Chamber Model
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Author : E. G. Hoholis
language : en
Publisher:
Release Date : 1985
Numerical Simulation And Experimental Investigation Of Jet Injection Into A Quiescent Combustion Chamber Model written by E. G. Hoholis and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 1985 with categories.
Numerical And Experimental Studies On Combustion Engines And Vehicles
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Author : Paweł Woś
language : en
Publisher: BoD – Books on Demand
Release Date : 2020-11-26
Numerical And Experimental Studies On Combustion Engines And Vehicles written by Paweł Woś and has been published by BoD – Books on Demand this book supported file pdf, txt, epub, kindle and other format this book has been release on 2020-11-26 with Technology & Engineering categories.
The matters discussed and presented in the chapters of this book cover a wide spectrum of topics and research methods commonly used in the field of engine combustion technology and vehicle functional systems. This book contains the results of both computational analyses and experimental studies on jet and reciprocating combustion engines as well heavy-duty onroad vehicles. Special attention is devoted to research and measures toward preventing the emission of harmful exhaust components, reducing fuel consumption or using unconventional methods of engine fueling or using renewable and alternative fuels in different applications. Some technical improvements in design and control of vehicle systems are also presented.
An Experimental And Numerical Investigation Of Sonic Fatigue In Embedded Jet Exhausts
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Author : Darryl Andrew Douglas
language : en
Publisher:
Release Date : 2023
An Experimental And Numerical Investigation Of Sonic Fatigue In Embedded Jet Exhausts written by Darryl Andrew Douglas and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2023 with categories.
Sonic fatigue is present in embedded jet exhaust systems of military aircraft due to a combination of supersonic exhaust velocities and the proximity of the exhaust to the aircraft fuselage. The source of this fatigue is due in part to shock turbulent boundary layer interaction (STBLI) and its characteristics need to be predicted early in the design of the aircraft. The goal of the present study is to improve the understanding of the physical mechanisms involved in shock turbulent boundary layer interaction in rectangular embedded jet exhausts. Model experiments are performed and the measurements used to assess steady and unsteady CFD predictions. Experiments were completed at three supersonic nozzle pressure ratio (NPR) conditions. These NPR are 2.30 (overexpanded), 2.62 (on-design), and 3.50 (underexpanded). The experiments included schlieren visualization and pressure measurements on the aft-deck surface. The schlieren visualization was performed using a Z-type schlieren system with a high speed digital camera. The pressure measurements were taken on the centerline, quarter span and half span using Endevco pressure transducers. Both steady Reynolds Averaged Navier-Stokes (RANS) and Hybrid RANS/LES (HLES) simulations were run. The steady RANS used the Menter shear stress transport (SST) turbulence model. The HLES method was developed by Bush and combines the SST turbulence model near the wall and LES away from walls. The experimental schlieren showed shock motion for all tested NPR's. The shockmotion occurred for all visible shocks in the streamwise direction starting from the nozzle exit through the visible portion of the jet. Expansions were visible exiting the nozzle and reflecting from the shear layer and aft-deck. Spectral Proper Orthogonal Decomposition (SPOD) showed that the frequency of shock motion including expansions from within the nozzle was in the hundreds of hertz. Pressure measurements on the aft-deck showed most PSD energy was at frequencies identical to the shock motion seen in the schlieren. The steady RANS and HLES results were compared to the experiments and used to understand the sources of the shock motion. The RANS pressure on the aft-deck compared well with the experiments for NPR's 2.30 and 3.50. The mean HLES improved the prediction of mean pressure local minima and maxima associated with shock intersections on the aft-deck surface for NPR's 2.30 and 3.50. NPR 2.62 did not have such good agreement with experiments for RANS or HLES. RMS pressure was overpredicted downstream of x/H = 1.7 for NPR 2.30 and downstream of x/H = 2.0 for NPR 3.50 on the centerline of the aft-deck. The overpredictions in RMS and PSD are argued to be due to a lack of both grid resolution in the nozzle wall boundary layer and incomplete prescription of experimental inflow boundary layer conditions. The low frequency unsteadiness of the shocks is due to vortices that develop within the nozzle at the walls and the oscillation of the separated region intrinsic to STBLI.
Research And Technology Program Digest Flash Index
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Author :
language : en
Publisher:
Release Date : 1967
Research And Technology Program Digest Flash Index written by and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 1967 with Astronautics categories.
