"The problem of acoustic radiation from turbofan engine inlets in flow has not lent itself fully to analysis by numerical means because of the large domains and high frequencies involved. This project has extended the use of finite elements and wave envelope elements, elements which simulate decay and wavelike behaviour in their interpolation functions, from the no-flow case in which they have been proven, to cases incorporating mean flow. By employing an irrotational mean flow assumption, the acoustics problem has been posed in an axisymmetric formulation in terms of acoustic velocity potential, thus minimising computer solution storage requirements. The wave envelope element interpolation functions are derived from the solution for the acoustic field for a harmonic monopole in a uniform mean flow, and the element geometry is based on the ray paths and constant phase surfaces for such a solution. The choice of such a mesh allows simple implementation of a far-field Sommerfeld radiation condition, in a manner similar to the no-flow case.
The results obtained from the numerical procedures agree well with known analytical solutions and static jet engine inflow experimental data. Some discrepancy with flight test data exists but the combined finite element-wave envelope element solution radiation directivity trends are in good agreement with analytical predictions"--Abstract, page ii.
Koval, Leslie Robert
Penico, Anthony J., 1923-2011
Batra, R. C.
Mechanical and Aerospace Engineering
Ph. D. in Mechanical Engineering
United States. National Aeronautics and Space Administration
University of Missouri--Rolla
xiii, 129 pages
© 1984 Alan Vincent Parrett, All rights reserved.
Dissertation - Restricted Access
Airplanes -- Turbojet engines
Finite element method
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Electronic access to the full-text of this document is restricted to Missouri S&T users. Otherwise, request this publication directly from Missouri S&T Library or contact your local library.http://merlin.lib.umsystem.edu/record=b1633380~S5
Parrett, A. V., "Applications of finite and wave envelope element approximations to acoustic radiation from turbofan engine inlets in flight" (1984). Doctoral Dissertations. 549.