Session: 01-09 Modelling, Simulation and Validation I

Paper Number: 154047

Methods for High-Speed Jet Exhaust Aero-Vibro-Acoustic Modeling in Engine Test Cells 

The primary design goal for enclosed ground-based high-performance jet engine test cell facilities is to provide a stable and repeatable aerodynamic environment in order to characterize key engine performance parameters. A second important consideration is management of the harsh acoustic environments created by the high-speed jet engine exhaust, which may lead to structural damage and/or failure, excessive personnel exposure, and/or community noise.  In the free-field, high-speed jets produce a highly-directive sound radiation pattern that may be comprised of multiple mechanisms. Noise control treatments in an enclosed facility must mitigate these loadings by properly targeting the frequency content of the sound as it is modified and amplified by the facility. This paper presents an aero-vibro-acoustic modeling strategy to characterize engine test cell interior acoustic environments by combining scale-resolving computational fluid dynamics (CFD) simulations, distributed equivalent acoustic source models, and boundary element methods (BEM) and statistical energy analysis (SEA) to characterize test-cell interior noise.  Wall-modeled large eddy simulations (WMLES) in both free-field and enclosed domains are generated to target the acoustic frequencies associated with large-scale mixing and shock-turbulent interaction sources.  Free-field WMLES is probed in the jet near-field in order to decompose the fluctuating pressure into a plurality of partial acoustic fields at each frequency of interest. Partial fields are then fit to an equivalent acoustic source model using an inverse methodology, and these sources are then introduced into an acoustic tool that predicts interior noise levels through a combination of BEM and gradient SEA methods.  At low frequencies, the BEM pressure spectra are first corrected to a “hardwall” WMLES simulation of interior noise levels and then used to examine the impact of noise control treatments which are characterized through impedance boundary conditions. At high frequencies, a directional point source is used in a gradient SEA model to capture the high-frequency roll-off. In addition to describing a practical, CFD-based methodology to characterize acoustic environments and perform trade studies of noise control solutions in engine test cells, the paper discusses some of the inherent challenges associated with defining approximate acoustic source models using free-field CFD alone. Specifically, the paper will discuss the possibility of strong fluid dynamic-acoustic coupling, or “lock-in”, which may result in catastrophic resonant feedback under certain conditions.  The understanding of such resonant responses is crucial to test cell facility design, and demonstrates the need for a multidisciplinary approach for the design of future test cells which combines aerodynamic and acoustic prediction methods, anchored to test measurements.

Presenting Author: Parthiv Shah ATA Engineering, Inc.

Presenting Author Biography: Dr. Parthiv Shah works as a senior technical advisor and is ATA’s technical director of Fluid Dynamics and Propulsion. His interests include aeroacoustics, turbomachinery, and fluid dynamics. Prior to commencing his doctoral studies at MIT, Dr. Shah worked in a variety of organizations within Pratt & Whitney (P&W) in East Hartford and Middletown, Connecticut, including the compressor aerodynamics and acoustics groups. Dr. Shah is also an active member of the ASME Aircraft Engine and Turbomachinery committees, and is an Associate Fellow of AIAA.

Authors:

Parthiv Shah ATA Engineering, Inc.
Michael Yang ATA Engineering, Inc.
Derek Berg ATA Engineering, Inc.
Stephen Hambric Hambric Acoustics, LLC
Darryl Douglas NAWCAD/Air Systems Group/Propulsion & Power
David Mayo, Jr. NAWCAD/Air Systems Group/Propulsion & Power
John Spyropoulos NAWCAD/Air Systems Group/Propulsion & Power
Ryan Denton RS&H