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 (NEAR) 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 non-locally reacting, liners. It also provides a compact, differential equation description of liner dynamics that may be employed immediately as a boundary condition in time-domain Computational Aeroacoustics calculations used to analyze performance of existing liners or design new ones. The ability to provide a nonlinear description of liner behavior makes NEAR's liner characterization method unique.
A feasibility study of the linear and nonlinear time-domain characterization of acoustic liner response has been conducted. We have demonstrated a robust identification scheme suitable for the derivation of ordinary differential equations (ODE) as liner boundary conditions. Our methodology involves three main steps: (1) fitting sparse liner response data with a physics-based interpolant, (2) performing the Volterra kernel identification using multiresolution pulse basis functions, and (3) fitting the extracted impulse response with complex exponentials from which the ODE coefficients are automatically derived. The linear version of the method was demonstrated on a constant depth ceramic tubular liner as well as a perforated plate resonator panel. Nonlinear extensions of the kernel identification scheme were demonstrated on nonlinear impedance data for a Helmholtz resonator.
- Keefe, L. R. and Reisenthel, P. H., "Nonlinear Time-Domain Boundary Conditions From Liner Response Data," NEAR TR 568, Nielsen Engineering & Research, Mountain View, CA, August 2001.
- Keefe, L. R., Reisenthel, P. H., and Love, J. F., "Time-Domain Nonlinear Characterization of Acoustic Liner Response," NEAR TR 601, Nielsen Engineering & Research, Mountain View, CA, Apr. 2004.
- Keefe, L. R., and Reisenthel, P.H., "Time-Domain Characterization of Acoustic Liner Response from Experimental Data. Part 1: Linear Response," AIAA 2005-3060, May 2005.
Unsteady Aerodynamics Modeling Based on Nonlinear Indicial Response Theory
Nonlinear Volterra Kernel Identification System for Aeroelastic Applications
Nonlinear Time-Domain Characterization of Acoustic Liners From Liner Response Data
Multidimensional Response Surface Technology