Author: Clifford Alan BrownPublisher:
ISBN:
Category :
Languages : en
Pages : 24
Book Description
Developing an empirical model for jet-surface interaction noise
Author: Clifford Alan BrownDeveloping an Empirical Model for Jet-Surface Interaction Noise
Author: National Aeronautics and Space Administration (NASA)Publisher: Createspace Independent Publishing Platform
ISBN: 9781719396714
Category :
Languages : en
Pages : 30
Book Description
The process of developing an empirical model for jet-surface interaction noise is described and the resulting model evaluated. Jet-surface interaction noise is generated when the high-speed engine exhaust from modern tightly integrated or conventional high-bypass ratio engine aircraft strikes or flows over the airframe surfaces. An empirical model based on an existing experimental database is developed for use in preliminary design system level studies where computation speed and range of configurations is valued over absolute accuracy to select the most promising (or eliminate the worst) possible designs. The model developed assumes that the jet-surface interaction noise spectra can be separated from the jet mixing noise and described as a parabolic function with three coefficients: peak amplitude, spectral width, and peak frequency. These coefficients are fit to functions of surface length and distance from the jet lipline to form a characteristic spectra which is then adjusted for changes in jet velocity and/or observer angle using scaling laws from published theoretical and experimental work. The resulting model is then evaluated for its ability to reproduce the characteristic spectra and then for reproducing spectra measured at other jet velocities and observer angles; successes and limitations are discussed considering the complexity of the jet-surface interaction noise versus the desire for a model that is simple to implement and quick to execute. Brown, Clifford A. Glenn Research Center AIRCRAFT DESIGN; NOISE PREDICTION; COMPUTERIZED SIMULATION; ACOUSTIC SIMULATION; AEROACOUSTICS; AERODYNAMIC NOISE; JET AIRCRAFT NOISE; SURFACE REACTIONS; COMPUTATIONAL AEROACOUSTICS; COMPUTATIONAL FLUID DYNAMICS; NOISE REDUCTION; NOISE MEASUREMENT; FLUID FLOW; ENGINE AIRFRAME INTEGRATION; COEFFICIENTS; FREQUENCIES; AIRFRAMES; TURBULENCE; TRAILING EDGES; NOISE SPECTRA; JET MIXING FLOW
A Semi-empirical Jet-surface Interaction Noise Model
Author: Martin Frederick DawsonPublisher:
ISBN:
Category :
Languages : en
Pages : 0
Book Description
Including Finite Surface Span Effects in Empirical Jet-surface Interaction Noise Models
Author: Clifford A. BrownA Model for Jet-surface Interaction Noise Using Physically Realizable Upstream Turbulence Conditions
Author: Mohammed Z. AfsarAn Empirical Model for Inverted-velocity-profile Jet Noise Prediction
Author: James R. StoneEmpirical Models for the Shielding and Reflection of Jet Mixing Noise by a Surface
Author: Development of an Empirical Methods for Predicting Jet Mixing Noise of Cold Flow Rectangular Jets
Author: National Aeronautics and Space Administration (NASA)Publisher: Createspace Independent Publishing Platform
ISBN: 9781720478560
Category :
Languages : en
Pages : 98
Book Description
This report presents an empirical method for predicting the jet mixing noise levels of cold flow rectangular jets. The report presents a detailed analysis of the methodology used in development of the prediction method. The empirical correlations used are based on narrow band acoustic data for cold flow rectangular model nozzle tests conducted in the NASA Langley Jet Noise Laboratory. There were 20 separate nozzle test operating conditions. For each operating condition 60 Hz bandwidth microphone measurements were made over a frequency range from 0 to 60,000 Hz. Measurements were performed at 16 polar directivity angles ranging from 45 degrees to 157.5 degrees. At each polar directivity angle, measurements were made at 9 azimuth directivity angles. The report shows the methods employed to remove screech tones and shock noise from the data in order to obtain the jet mixing noise component. The jet mixing noise was defined in terms of one third octave band spectral content, polar and azimuth directivity, and overall power level. Empirical correlations were performed over the range of test conditions to define each of these jet mixing noise parameters as a function of aspect ratio, jet velocity, and polar and azimuth directivity angles. The report presents the method for predicting the overall power level, the average polar directivity, the azimuth directivity and the location and shape of the spectra for jet mixing noise of cold flow rectangular jets.Russell, James W.Langley Research CenterAEROACOUSTICS; PREDICTION ANALYSIS TECHNIQUES; AERODYNAMIC NOISE; JET MIXING FLOW; COLD FLOW TESTS; ACOUSTIC FREQUENCIES; DATA REDUCTION; MICROPHONES; SCREECH TONES; SHOCK WAVES; NARROWBAND; AZIMUTH; NOZZLE GEOMETRY
Development of an Empirical Method for Predicting Jet Mixing Noise of Cold Flow Rectangular Jets
Author: James W. RussellPublisher:
ISBN:
Category : Acoustical engineering
Languages : en
Pages : 88
Book Description
This report presents an empirical method for predicting the jet mixing noise levels of cold flow rectangular jets. The report presents a detailed analysis of the methodology used in development of the prediction method. The empirical correlations used are based on narrow band acoustic data for cold flow rectangular model nozzle tests conducted in the NASA Langley Jet Noise Laboratory. There were 20 separate nozzle test operating conditions. For each operating condition 60 Hz bandwidth microphone measurements were made over a frequency range from 0 to 60,000 Hz. Measurements were performed at 16 polar directivity angles ranging from 45 degrees to 157.5 degrees. At each polar directivity angle, measurements were made at 9 azimuth directivity angles. The report shows the methods employed to remove screech tones and shock noise from the data in order to obtain the jet mixing noise component. The jet mixing noise was defined in terms of one third octave band spectral content, polar and azimuth directivity, and overall power level. Empirical correlations were performed over the range of test conditions to define each of these jet mixing noise parameters as a function of aspect ratio, jet velocity, and polar and azimuth directivity angles. The report presents the method for predicting the overall power level, the average polar directivity, the azimuth directivity, and the location and shape of the spectra for jet mixing noise of cold flow rectangular jets.
Author: Gary G. Podboy