Download or read book Prediction of Turbulence Generated Noise in Unheated Jets Part 1 Jeno Technical Manual Version 1 0 written by National Aeronautics and Space Administration (NASA) and published by Createspace Independent Publishing Platform. This book was released on 2018-06-03 with total page 48 pages. Available in PDF, EPUB and Kindle. Book excerpt: The model-based approach, used by the JeNo code to predict jet noise spectral directivity, is described. A linearized form of Lilley's equation governs the non-causal Green s function of interest, with the non-linear terms on the right hand side identified as the source. A Reynolds-averaged Navier-Stokes (RANS) solution yields the required mean flow for the solution of the propagation Green s function in a locally parallel flow. The RANS solution also produces time- and length-scales needed to model the non-compact source, the turbulent velocity correlation tensor, with exponential temporal and spatial functions. It is shown that while an exact non-causal Green s function accurately predicts the observed shift in the location of the spectrum peak with angle as well as the angularity of sound at low to moderate Mach numbers, the polar directivity of radiated sound is not entirely captured by this Green s function at high subsonic and supersonic acoustic Mach numbers. Results presented for unheated jets in the Mach number range of 0.51 to 1.8 suggest that near the peak radiation angle of high-speed jets, a different source/Green s function convolution integral may be required in order to capture the peak observed directivity of jet noise. A sample Mach 0.90 heated jet is also discussed that highlights the requirements for a comprehensive jet noise prediction model.Khavaran, Abbas and Bridges, James and Georgiadis, NicholasGlenn Research CenterNOISE PREDICTION; TURBULENCE; JET AIRCRAFT NOISE; CONVOLUTION INTEGRALS; EXPONENTIAL FUNCTIONS; MACH NUMBER; MATHEMATICAL MODELS; SUPERSONIC SPEED
Download or read book Prediction of Turbulence Generated Noise in Unheated Jets written by Nasa Technical Reports Server (Ntrs) and published by BiblioGov. This book was released on 2013-07-01 with total page 50 pages. Available in PDF, EPUB and Kindle. Book excerpt: The NASA Technical Reports Server (NTRS) houses half a million publications that are a valuable means of information to researchers, teachers, students, and the general public. These documents are all aerospace related with much scientific and technical information created or funded by NASA. Some types of documents include conference papers, research reports, meeting papers, journal articles and more. This is one of those documents.
Download or read book Numerical Simulation of Turbulent Jet Noise Part 1 written by and published by . This book was released on 1975 with total page 80 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Modeling of Turbulence Generated Noise in Jets written by National Aeronautics and Space Administration (NASA) and published by Createspace Independent Publishing Platform. This book was released on 2018-06-21 with total page 24 pages. Available in PDF, EPUB and Kindle. Book excerpt: A numerically calculated Green's function is used to predict jet noise spectrum and its far-field directivity. A linearized form of Lilley's equation governs the non-causal Green s function of interest, with the non-linear terms on the right hand side identified as the source. In this paper, contributions from the so-called self- and shear-noise source terms will be discussed. A Reynolds-averaged Navier-Stokes solution yields the required mean flow as well as time- and length scales of a noise-generating turbulent eddy. A non-compact source, with exponential temporal and spatial functions, is used to describe the turbulence velocity correlation tensors. It is shown that while an exact non-causal Green's function accurately predicts the observed shift in the location of the spectrum peak with angle as well as the angularity of sound at moderate Mach numbers, at high subsonic and supersonic acoustic Mach numbers the polar directivity of radiated sound is not entirely captured by this Green's function. Results presented for Mach 0.5 and 0.9 isothermal jets, as well as a Mach 0.8 hot jet conclude that near the peak radiation angle a different source/Green's function convolution integral may be required in order to capture the peak observed directivity of jet noise. Khavaran, Abbas and Bridges, James Glenn Research Center NASA/TM-2004-213105, AIAA Paper 2004-2983, E-14580
Download or read book Model for prediction of jet noise from measurements of fluctuating turbulent stresses written by Ian Stanley Ferguson Jones and published by . This book was released on 1967 with total page 60 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Noise Produced by Turbulent Flow Into a Rotor written by National Aeronautics and Space Administration (NASA) and published by Createspace Independent Publishing Platform. This book was released on 2018-07-09 with total page 44 pages. Available in PDF, EPUB and Kindle. Book excerpt: A users manual for a computer program for predicting atmospheric turbulence and mean flow and turbulence contraction as part of a noise prediction scheme for nonisotropic turbulence ingestion noise in helicopters is described. Included are descriptions of the various program modules and subroutines, their function, programming structure, and the required input and output variables. This routine is incorporated as one module of NASA's ROTONET helicopter noise prediction program. Simonich, J. C. and Caplin, B. Unspecified Center NAS1-17763; RTOP 505-63-51...
Download or read book Jet Noise A Survey and a Prediction for Subsonic Flows written by Philip T. Harsha and published by . This book was released on 1975 with total page 78 pages. Available in PDF, EPUB and Kindle. Book excerpt: The state-of-the-art of the prediction of turbulent jet noise is surveyed. This survey includes a description of the available experimental data on subsonic and supersonic, cold and hot jets, and of present theoretical treatments of the mechanisms of turbulent jet noise production. A detailed analysis of the production of subsonic cold jet noise, based on the acoustic analogy formulation, is described, and results of computations using this analysis and a turbulent kinetic energy analysis of the jet flow field are presented and compared with representative experimental data.
Download or read book Aircraft Noise Prediction Program Theoretical Manual written by National Aeronautics and Space Administration (NASA) and published by Createspace Independent Publishing Platform. This book was released on 2018-07-23 with total page 276 pages. Available in PDF, EPUB and Kindle. Book excerpt: This document describes the theoretical methods used in the rotorcraft noise prediction system (ROTONET), which is a part of the NASA Aircraft Noise Prediction Program (ANOPP). The ANOPP code consists of an executive, database manager, and prediction modules for jet engine, propeller, and rotor noise. The ROTONET subsystem contains modules for the prediction of rotor airloads and performance with momentum theory and prescribed wake aerodynamics, rotor tone noise with compact chordwise and full-surface solutions to the Ffowcs-Williams-Hawkings equations, semiempirical airfoil broadband noise, and turbulence ingestion broadband noise. Flight dynamics, atmosphere propagation, and noise metric calculations are covered in NASA TM-83199, Parts 1, 2, and 3. Weir, Donald S. and Jumper, Stephen J. and Burley, Casey L. and Golub, Robert A. Langley Research Center NASA-TM-83199-PT-4, L-16700-PT-4, NAS 1.15:83199-PT-4 RTOP 532-06-37-01...
Download or read book On Inm s Use of Corrected Net Thrust for the Prediction of Jet Aircraft Noise written by Nasa Technical Reports Server (Ntrs) and published by BiblioGov. This book was released on 2013-06 with total page 24 pages. Available in PDF, EPUB and Kindle. Book excerpt: The Federal Aviation Administration s (FAA) Integrated Noise Model (INM) employs a prediction methodology that relies on corrected net thrust as the sole correlating parameter between aircraft and engine operating states and aircraft noise. Thus aircraft noise measured for one set of atmospheric and aircraft operating conditions is assumed to be applicable to all other conditions as long as the corrected net thrust remains constant. This hypothesis is investigated under two primary assumptions: (1) the sound field generated by the aircraft is dominated by jet noise, and (2) the sound field generated by the jet flow is adequately described by Lighthill s theory of noise generated by turbulence.
Download or read book Aircraft Noise Prediction Program User s Manual written by Ronnie E. Gillian and published by . This book was released on 1982 with total page 340 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Jet Aeroacoustics written by National Aeronautics and Space Adm Nasa and published by Independently Published. This book was released on 2019 with total page 34 pages. Available in PDF, EPUB and Kindle. Book excerpt: Progress associated with research in (1) physics and prediction of turbulent mixing noise from supersonic jets, and (2) numerical simulation of supersonic jet noise is reported. Tam, Christopher Langley Research Center NASA-CR-203579, NAS 1.26:203579 NAG1-1776...
Download or read book Supersonic Jet Exhaust Noise Investigation written by David R. Ferguson and published by . This book was released on 1976 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: This report gives a detailed description of aerodynamic (Shock-free/Shocked flow) and acoustic turbulent mixing computer prediction programs developed by the General Electric Company for subsonic and supersonic simple exhaust jets. In addition to giving detailed descriptions of the aeroacoustic formulations and discussions of computer manual instructions for operating the program, extensive theory/data comparisons are given, as well as computer program listings and sample test cases. (Author).
Download or read book Fundamental Study of Jet Noise Generation and Suppression Volume 1 Experimental and Theoretical Investigations of Model Jet Exhaust Stream Noise and the Development of Normalizing Parameters for Size and Temperature written by and published by . This book was released on 1963 with total page 211 pages. Available in PDF, EPUB and Kindle. Book excerpt: Part 1: Far-field sound pressure levels were measured in an anechoic room for noise generated by cold air flow through a wide variety of small nozzle configurations including converging, converging diverging, and annular types with and without center core flow. The results are examined in terms of flow and acoustic power performance, directivity, and power spectral density. Normalization parameters are developed for both size and temperature which show good agreement between flow and acoustic performance of small cold jet nozzles, large hot jet nozzles, and jet engines. A particular configuration of annular plug nozzles exhibited remarkably good acoustic performance with no measurable loss of mass flow performance. Part 2: A simplified theory on the acoustical attenuation qualities of an extended plug nozzle is presented. The theory is based upon similarity relationships and on the location of shock structure, a parameter which remains constant in supersonic flow. Theoretical curves of noise attenuation versus nozzle geometrical parameters show reasonable agreement with our experimental cold jet results for a nozzle exhibiting ten to fifteen decibels reduction over a wide mass flow range. Design criteria is given which indicate that twenty or more decibels reduction may be accomplished by an optimally designed nozzle.
Download or read book A Coupled Large Eddy Simulation synthetic Turbulence Method for Predicting Jet Noise written by Joshua Daniel Blake and published by . This book was released on 2020 with total page 203 pages. Available in PDF, EPUB and Kindle. Book excerpt: The noise generated by jet engines represents a significant environmental concern that still needs to be addressed. Accurate and efficient numerical predictions are a key step towards reducing jet noise. The current standard in high-fidelity prediction of jet noise is large eddy simulation (LES), which resolves the large turbulent scales responsible for the low and medium frequency noise and models the smallest turbulent scales that correspond to the high frequency noise. While LES requires significant computational resources to produce an accurate solution, it fails to resolve the noise in the high frequency range, which cannot be simply ignored. To circumvent this, in this dissertation the Coupled LES-Synthetic Turbulent method (CLST) was developed to model the missing frequencies that relate to un-resolved sub-grid scale fluctuations in the flow. The CLST method combines the resolved, large-scale turbulent fluctuations from very large eddy simulations (VLES) with modeled, small-scale fluctuations from a synthetic turbulence model. The noise field is predicted using a formulation of the linearized Euler equations (LEE), where the acoustic waves are generated by source terms from the combined fluctuations of the VLES and the synthetic fields. This research investigates both a Fourier mode-based stochastic turbulence model and a synthetic eddy-based turbulence model in the CLST framework. The Fourier mode-based method is computationally less expensive than the synthetic eddy method but does not account for sweeping. Sweeping and straining of the synthetic fluctuations by large flow scales from VLES are accounted for in the synthetic eddy method. The two models are tested on a Mach 0.9 jet at a moderately-high Reynolds number and at a low Reynolds number. The CLST method is an efficient and viable alternative to high resolution LES or DNS because it can resolve the high frequency range in the acoustic noise spectrum at a reasonable expense.
Download or read book A Generalized Wall Function written by and published by . This book was released on 1999 with total page 26 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Grinding and Lapping written by and published by . This book was released on 1909 with total page 54 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Strategic Antisubmarine Warfare and Naval Strategy written by Tom Stefanick and published by Free Press. This book was released on 1987 with total page 432 pages. Available in PDF, EPUB and Kindle. Book excerpt:
