Author: E. Grande
Publisher:
ISBN:
Category :
Languages : en
Pages : 0
Book Description
The refraction of the sound field of an omnidirectional pure tone 'point' source of sound by the temperature and velocity fields of a 3/4 inch air or nitrogen jet was measured. Several source positions were employed: one within the potential core, others entirely outside the jet. For the source in the on-axis position, the air jet velocity was varied between M = 0.5 and 0.95 at fixed source frequency and ambient jet temperature, yielding a characteristic axial refraction valley, e.g., -35dB at M = 0.95 and 3000 c.p.s. Similar, but asymmetric patterns were obtained with the source outside the jet. Using a very cold nitrogen jet (T = -180C), the sound was found to be refracted inward - a focusing effect - to yield an intensity lobe along the jet axis; e.g. +26dB at M = 0.11 and 7000 c.p.s. For both the cold jet and the ambient jet the ordinary jet noise was measured in narrow filter bands: the respective polar plots exhibited the same general shape near the axis as those for the injected pure tones. The filtered jet noise polar plots were also 'corrected' for refraction (using the pure-tone patterns) and for convection (via theory) to yield the approximate 'basic directivity' of the eddy sources: the polar patterns resemble ellipses of low eccentricity, rather unlike Lighthill's four-leaf-clover. (Author).
Refraction of Sound by Jet Flow and Jet Temperature Ii
Author: E. Grande
Publisher:
ISBN:
Category :
Languages : en
Pages : 0
Book Description
The refraction of the sound field of an omnidirectional pure tone 'point' source of sound by the temperature and velocity fields of a 3/4 inch air or nitrogen jet was measured. Several source positions were employed: one within the potential core, others entirely outside the jet. For the source in the on-axis position, the air jet velocity was varied between M = 0.5 and 0.95 at fixed source frequency and ambient jet temperature, yielding a characteristic axial refraction valley, e.g., -35dB at M = 0.95 and 3000 c.p.s. Similar, but asymmetric patterns were obtained with the source outside the jet. Using a very cold nitrogen jet (T = -180C), the sound was found to be refracted inward - a focusing effect - to yield an intensity lobe along the jet axis; e.g. +26dB at M = 0.11 and 7000 c.p.s. For both the cold jet and the ambient jet the ordinary jet noise was measured in narrow filter bands: the respective polar plots exhibited the same general shape near the axis as those for the injected pure tones. The filtered jet noise polar plots were also 'corrected' for refraction (using the pure-tone patterns) and for convection (via theory) to yield the approximate 'basic directivity' of the eddy sources: the polar patterns resemble ellipses of low eccentricity, rather unlike Lighthill's four-leaf-clover. (Author).
Publisher:
ISBN:
Category :
Languages : en
Pages : 0
Book Description
The refraction of the sound field of an omnidirectional pure tone 'point' source of sound by the temperature and velocity fields of a 3/4 inch air or nitrogen jet was measured. Several source positions were employed: one within the potential core, others entirely outside the jet. For the source in the on-axis position, the air jet velocity was varied between M = 0.5 and 0.95 at fixed source frequency and ambient jet temperature, yielding a characteristic axial refraction valley, e.g., -35dB at M = 0.95 and 3000 c.p.s. Similar, but asymmetric patterns were obtained with the source outside the jet. Using a very cold nitrogen jet (T = -180C), the sound was found to be refracted inward - a focusing effect - to yield an intensity lobe along the jet axis; e.g. +26dB at M = 0.11 and 7000 c.p.s. For both the cold jet and the ambient jet the ordinary jet noise was measured in narrow filter bands: the respective polar plots exhibited the same general shape near the axis as those for the injected pure tones. The filtered jet noise polar plots were also 'corrected' for refraction (using the pure-tone patterns) and for convection (via theory) to yield the approximate 'basic directivity' of the eddy sources: the polar patterns resemble ellipses of low eccentricity, rather unlike Lighthill's four-leaf-clover. (Author).
Refraction of Sound by Jet Flow and Jet Temperature
Author: E. Grande
Publisher: Institute for Aerospace Studies, University of Toronto
ISBN:
Category : Aerodynamic noise
Languages : en
Pages : 60
Book Description
Publisher: Institute for Aerospace Studies, University of Toronto
ISBN:
Category : Aerodynamic noise
Languages : en
Pages : 60
Book Description
Effects of Temperature-profile Variation on Refraction of Sound by Jet Flow
Author: Jay C. Hardin
Publisher:
ISBN:
Category : Aerodynamic noise
Languages : en
Pages : 36
Book Description
Publisher:
ISBN:
Category : Aerodynamic noise
Languages : en
Pages : 36
Book Description
Refraction of Sound by Jet Flow Or Jet Temperature
Author: J. Atvars
Publisher: Institute for Aerospace Studies, University of Toronto
ISBN:
Category : Jet plane sounds
Languages : en
Pages : 44
Book Description
The heart-shaped pattern of subsonic jet noise normally peaks somewhere between 15 degrees and 45 degrees from the axis, depending on conditions, falling off sharply as the axis is approached. Conflicting explanations of this directivity pattern appear in the literature. The present investigation suggests that the deep cleft in the pattern can be attributed mainly to refraction of the sound out of the jet by the velocity and temperature fields. The evidence lies in measurements made of the sound field of a harmonic 'point' source placed within a 3/4 in. dia. air jet. The source is the orifice of a tube about 1/16 in. i.d. driven through a conical coupling by a horn-type loudspeaker driver; this radiates sound essentially omnidirectionally up to about 15,000 cps. The experiment established the formation of an axial intensity minimum, which appears to be mainly due to refraction. The depth of the refraction valley increases with jet velocity, jet temperature, and sound frequency; a depth corresponding to an intensity reduction of the order of 35 dB is attained at M = 0.9 for 3000 cps. (Author).
Publisher: Institute for Aerospace Studies, University of Toronto
ISBN:
Category : Jet plane sounds
Languages : en
Pages : 44
Book Description
The heart-shaped pattern of subsonic jet noise normally peaks somewhere between 15 degrees and 45 degrees from the axis, depending on conditions, falling off sharply as the axis is approached. Conflicting explanations of this directivity pattern appear in the literature. The present investigation suggests that the deep cleft in the pattern can be attributed mainly to refraction of the sound out of the jet by the velocity and temperature fields. The evidence lies in measurements made of the sound field of a harmonic 'point' source placed within a 3/4 in. dia. air jet. The source is the orifice of a tube about 1/16 in. i.d. driven through a conical coupling by a horn-type loudspeaker driver; this radiates sound essentially omnidirectionally up to about 15,000 cps. The experiment established the formation of an axial intensity minimum, which appears to be mainly due to refraction. The depth of the refraction valley increases with jet velocity, jet temperature, and sound frequency; a depth corresponding to an intensity reduction of the order of 35 dB is attained at M = 0.9 for 3000 cps. (Author).
Refraction of Sound by Jet Flow Or Jet Temperature
Author: University of Toronto. Institute for Aerospace Studies
Publisher:
ISBN:
Category :
Languages : en
Pages : 18
Book Description
Publisher:
ISBN:
Category :
Languages : en
Pages : 18
Book Description
Refraction of Sound by Jet Flow and Jet Temperature
Author:
Publisher:
ISBN:
Category : Jet plane sounds
Languages : en
Pages :
Book Description
Publisher:
ISBN:
Category : Jet plane sounds
Languages : en
Pages :
Book Description
Suppression of Refraction in Jet Noise by Cooling
Author: J. T. Kelsall
Publisher:
ISBN:
Category : Aerodynamic noise
Languages : en
Pages : 23
Book Description
Noise generation in an air jet can be described in terms of a convection factor. The velocity gradients in the flow refract the sound, giving rise to a commonly observed final directivity. In the experiments outlined here the effects of convection and refraction on directivity are examined for a jet of very cold air. An attempt is made to determine whether any interdependence between convection and refraction can be detected experimentally in narrow band jet noise data. In the reported investigation liquid nitrogen was used to cool a jet of air (at nozzle speeds 0.21 to 0.28 of ambient sound speed) down to temperatures (between -110C and -155C) at which the refraction from the opposed velocity and temperature gradients produced cancellation effects.
Publisher:
ISBN:
Category : Aerodynamic noise
Languages : en
Pages : 23
Book Description
Noise generation in an air jet can be described in terms of a convection factor. The velocity gradients in the flow refract the sound, giving rise to a commonly observed final directivity. In the experiments outlined here the effects of convection and refraction on directivity are examined for a jet of very cold air. An attempt is made to determine whether any interdependence between convection and refraction can be detected experimentally in narrow band jet noise data. In the reported investigation liquid nitrogen was used to cool a jet of air (at nozzle speeds 0.21 to 0.28 of ambient sound speed) down to temperatures (between -110C and -155C) at which the refraction from the opposed velocity and temperature gradients produced cancellation effects.
Refraction of High Frequency Noise in an Arbitrary Jet Flow
Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 18
Book Description
Publisher:
ISBN:
Category :
Languages : en
Pages : 18
Book Description
Aerodynamically Generated Sound
Author: H. S. Ribner
Publisher:
ISBN:
Category :
Languages : en
Pages : 26
Book Description
Progress is reported on six research projects as follows: Turbulence measurements relevant to jet noise; Role of refraction in jet noise; 'Basic' directivity and spectra of jet noise; Computer study of refraction of sound by jet flow and jet temperature; Pressure fluctuations on a plate with oblique jet impingement; Distortion of a shock wave traversed by a vortex; Acoustic energy flux from shock-turbulence interaction.
Publisher:
ISBN:
Category :
Languages : en
Pages : 26
Book Description
Progress is reported on six research projects as follows: Turbulence measurements relevant to jet noise; Role of refraction in jet noise; 'Basic' directivity and spectra of jet noise; Computer study of refraction of sound by jet flow and jet temperature; Pressure fluctuations on a plate with oblique jet impingement; Distortion of a shock wave traversed by a vortex; Acoustic energy flux from shock-turbulence interaction.
NASA Technical Note
Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 492
Book Description
Publisher:
ISBN:
Category :
Languages : en
Pages : 492
Book Description