Doctoral Dissertations

Abstract

"The primary purpose of this research was to investigate the effects of flow and finite amplitude waves on the response of acoustic elements. A further purpose was to evaluate the effects of elevated temperatures and cross-sectional dimensions on element performance. As an integral part of this work various laboratory techniques were explored for their suitability.

Empirical models for the acoustic impedance of side branch resonators were developed for the two operational modes, i.e., flow past the resonator and finite amplitude wave inputs. A description of the complex variation of the acoustic resistance of the resonator with flow past and variable input level is given. A region characterized by high input levels was found in which the resistance becomes a linear function of the flow Mach number. Empirical factors to account for effects of finite amplitudes and steady flow are presented. In addition to the impedance measurements conducted on the resonators, response measurements were obtained and compared to those generated using the empirical impedance expressions for both cold and heated flow operations. Good agreement was obtained between measured and calculated response parameters, indicating the validity of the developed models.

A flow perturbation technique was employed to analytically describe the acoustic response of area discontinuities in the presence of steady flow. An adiabatic process was used to describe a simple expansion and an isentropic process was used for the simple contraction. Measurements of the response of simple expansion chambers under cold and heated flow operations agreed well with the response calculated using the developed models. No finite amplitude effects were observed at incident sound levels up to 150 dB. Measurements were also obtained for combinations of resonators and simple expansion chambers and compared well with the generated response. The analytic models and empirical relations developed in this work can be used to design sidebranch resonators and simple expansion chambers to attenuate finite amplitude sound waves superimposed upon a steady flow.

Modifications to an existing laboratory facility at University of Missouri-Rolla are described. These modifications were necessary to enable the experimental portion of this work to be accomplished. An anechoic termination capable of use with flow was constructed and its design, fabrication and evaluation are discussed"--Abstract, pages ii-iii.

Advisor(s)

Gatley, William S.

Committee Member(s)

Koval, Leslie Robert
Barker, Clark R.
Foster, J. Earl
Faucett, T. R.
Penico, Anthony J., 1923-2011

Department(s)

Mechanical and Aerospace Engineering

Degree Name

Ph. D. in Mechanical Engineering

Publisher

University of Missouri--Rolla

Publication Date

1972

Pagination

xvii, 205 pages

Note about bibliography

Includes bibliographical references (pages 180-182).

Rights

© 1972 Raymond Hershel Schaffart, All rights reserved.

Document Type

Dissertation - Open Access

File Type

text

Language

English

Subject Headings

Sound-waves -- Mathematical modelsSound-waves -- AttenuationSound-waves -- Transmission

Thesis Number

T 2800

Print OCLC #

6024774

Electronic OCLC #

904618511

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