| PROPOSAL NUMBER: | 02.01-8355 (For NASA Use Only - Chron: 001646 ) |
| PROPOSAL TITLE: | Time-Domain Nonlinear Characterization of Acoustic Liner Response |
TECHNICAL ABSTRACT (LIMIT 200 WORDS)
Suppression of jet engine noise by inlet and exhaust duct liners continues to be an important part of obtaining environmentally acceptable aircraft. To facilitate the design and analysis of both current perforate and mesh liners, as well as future active, smart, or nonlinearly responding liners, Nielsen Engineering and Research has developed a time-domain acoustic liner characterization scheme based on novel application of Volterra (integral) series methods. Rigorously equivalent to the conventional frequency-domain impedance concept for linearly behaving liners, the new method both generalizes and supersedes the impedance concept when faced with describing nonlinearly responding, and nonlocally reacting, liners. It also provides a compact, differential equation description of liner dynamics that may be employed as a boundary condition in time-domain Computational Aeroacoustics calculations used to analyze performance of existing liners or design new ones. In the Phase II Nielsen Engineering and Research will demonstrate this technique on nonlinear liners. This will include the design and testing, in collaboration with NASA, of new experimental techniques to provide the information-rich data needed for proper nonlinear characterization of liner dynamics. Numerical validations of the method are also included, beginning with end-to-end demonstrations of the method's ability to repredict the time-domain data upon which a liner's nonlinear description is based, and closing with realistic, full-Euler calculations of such liners installed in a representative engine inlet duct.
POTENTIAL COMMERCIAL APPLICATIONS
From this work NEAR envisions production of a software system that can be fed either time history or impedance data from liner measurements and then generates the particular differential equation that characterizes that liner's velocity response to pressure. This technique enables off-line liner design, optimization, and testing, with consequent savings to jet engine manufacturers. Use of this characterization technology outside acoustics could revive the use of simple, lumped-element, engineering models by eliminating the often restrictive assumptions associated with them. The ability to generate an approximate differential equation description of complex systems from data is a substantial accomplishment in that direction. Thus NEAR envisions a broader market for this characterization software in the simulation arena.
NAME AND ADDRESS OF PRINCIPAL INVESTIGATOR
(Name, Organization Name, Mail Address, City/State/Zip)
Patrick H. Reisenthel
Nielsen Engineering & Research, Inc.
526 Clyde Avenue
Mountain View , CA 94043 - 2212
NAME AND ADDRESS OF OFFEROR
(Firm Name, Mail Address, City/State/Zip)
Nielsen Engineering & Research, Inc.
526 Clyde Avenue
Mountain View , CA 94043 - 2212