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Record 4 of 66
Acoustic Energy Estimates in Inhomogeneous Moving Media
Offline Availability: Go to Request Form
Author and Affiliation:
Farassat, F.(NASA Langley Research Center, Hampton, VA, United States)
Farris, Mark(Midwestern State Univ., Wichita Falls, TX, United States)
Abstract: In ducted fan engine noise research, there is a need for defining a simple and easy to use acoustic energy conservation law to help in quantification of noise control techniques. There is a well known conservation law relating acoustic energy and acoustic energy flux in the case of an isentropic irrotational flow. Several different approaches have been taken to generalize this conservation law. For example, Morfey finds an identity by separating out the irrotational part of the perturbed flow. Myers is able to find a series of indentities by observing an algebraic relationship between the basic conservation of energy equation for a background flow and the underlying equations of motion. In an approximate sense, this algebraic relationship is preserved under perturbation. A third approach which seems to have not been pursued in the literature is a result known as Noether's theorem. There is a Lagrangian formulation for the Euler equation of fluid mechanics. Noether's theorem says that any group action that leaves the Lagrangian action invariant leads to a conserved quantity. This presentation will include a survey of current results regarding acoustic energy and preliminary results on the symmetries of the Lagrangian.
Publication Date: Jan 01, 1999
Document ID:
20040086689
(Acquired Aug 30, 2004)
Subject Category: AIRCRAFT PROPULSION AND POWER
Document Type: Conference Paper
Meeting Information: Joint ASA/EAA/DAGA Meeting; 14-19 Mar. 1999; Berlin; Germany
Meeting Sponsor: Acoustical Society of America; United States
European Acoustics Association; Unknown
German Acoustical Society; Germany
Financial Sponsor: NASA Langley Research Center; Hampton, VA, United States
Organization Source: NASA Langley Research Center; Hampton, VA, United States
Description: 16p; In English
Distribution Limits: Unclassified; Publicly available; Unlimited
Rights: No Copyright
NASA Terms: ACOUSTIC EMISSION; CONSERVATION LAWS; ENERGY CONSERVATION; EULER-LAGRANGE EQUATION; INHOMOGENEITY; WAVE PROPAGATION; ENGINE NOISE
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