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
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

Author:

Publisher:

Published: 1963

Total Pages: 211

ISBN-13:

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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.

Fundamental Study of Jet Noise Generation and Suppression
Fundamental Study of Jet Noise Generation and Suppression

Author: W. C. SPERRY

Publisher:

Published: 1960

Total Pages: 1

ISBN-13:

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THE FUNDAMENTAL ASPECTS OF JET NOISE GENERATION AND SUPPRESSION ARE EXAMINED AND EVALUATED. Initially, the basic equations of acoustics and fluid dynamics are considered with respect to the usual simplifying assumptions; the non-linear characteristics that lead to increased generality are emphasized. The Lighthill theory of subsonic jet stream noise and theories of supersonic jet stream noise are studied and extended. An analytical representation for the sound field surrounding a jet is provided which yields a solution giving some insight to noise generating mechanisms. Finally, a general review and analysis is provided of the experimental studies of others concerning jet noise generation and suppression. Volume I contains the technical details and Volume II is a bibliography. (Author).

Experimental and Theoretical Studies of Jet Noise Phenomena
Experimental and Theoretical Studies of Jet Noise Phenomena

Author: Willard Charles Sperry

Publisher:

Published: 1962

Total Pages: 358

ISBN-13:

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Over-all sound pressure levels were measured in an anechoic room for noise generated by cold air flow through more than twenty different nozzle configurations including converging, converging-diverging, slot, and annular types, the latter with and without center core flow. The results are examined in terms of over-all acoustic power and directivity versus mass flow and compared with various eighth power relations. The acoustic performance of most nozzles was similar in the subsonic region. However, certain annular type nozzles exhibited a marked superiority in the supersonic region. Theoretical discussions are presented concerning the generation of sound and the relationship between various turbulence and statistical theories. A modified mixing length theory is developed showing its application to turbulence generation as well as its influence on the general forcing function equation. Temperature effects are included. Empirical data are given pertaining to the correlation of jet noise from circular and annular nozzles. (Author).

Research on Jet Noise Generation and Suppression
Research on Jet Noise Generation and Suppression

Author: W. R. Semrau

Publisher:

Published: 1964

Total Pages: 240

ISBN-13:

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Experimental and analytical investigations on jet noise generation and suppression have resulted in a verification of the concept that jet noise is uniquely related to mean flow velocity distribution in the jet wake. Advances have been made in analytical techniques for calculating aerodynamic properties of free jet flow and the related acoustic properties of the flow and verification of the assumption that negligible attenuation of sound occurs during propagation through multi-element jet flows has been achieved. Investigation of selective water injection as a jet noise suppression scheme has indicated little promise for in-flight noise reduction. Studies of noise generation by high temperature and high pressure ratio jets have extended the state-of-the-art in the area of high temperature flow noise suppression, and have resulted in a means for predicting total acoustic power beyond the limits of applicability of the Lighthill parameter. (Author).