DATE: 10.24.24
TIME: 4:00pm
LOCATION: 31-218
SPEAKER: Dr. Parthiv Shah
TOPIC: Wind Tunnel Continuous-Scan Acoustic Analysis of Ducted Fan Tones Interacting with a Shielding Wall
ABSTRACT:
High-bypass ratio ducted fans emit tonal and broadband noise in both forward and aft directions. While produced by common mechanisms, the noise radiating in each direction is typically treated as its own directional source. Proper separation of forward- and aft-directed fan noise enables more efficient noise suppression strategies. This presentation examines wind tunnel continuous-scan acoustic measurements of a ducted fan analyzed with and without a barrier wall structure (which separates forward-emitted fan noise from the aft-emitted fan noise through shielding). The goal of this work is to use scanning (i.e., continuously-moving) microphone data to 1) decompose isolated fan noise measured in NASA Glenn’s 9x15 low-speed wind tunnel into respective aft and forward emitted tonal source models and 2) predict the fan tone interaction with a barrier wall. Acoustic signals from the scanning microphone are combined with a once-per-revolution tachometer signal to separate each shaft harmonic tone’s amplitude and phase in the time domain. The complex pressure envelope obtained from this decomposition is fit to an axially distributed ring source model by solving an inverse problem. The source model is verified against the isolated tunnel measurement data and then projected with a line-of-sight barrier wall shielding effect to compare to measurements with the barrier wall. Results suggest that the source model localizes the fan sources well enough to perform analytical source separation, offering the potential to eliminate the barrier wall from testing, which would provide a substantial time or cost savings. As acoustic shielding is also an important noise reduction strategy for next-generation aircraft, the barrier wall is an effective surrogate to study the effect of propulsion airframe aeroacoustics (PAA), where the wall creates shielding and/or scattering similar to a wing or airframe surface.
BIO:
Dr. Shah works as a Senior Technical Advisor and is ATA’s Technical Director of Fluid Dynamics and Propulsion. His interests include fluid dynamics, and aeroacoustics, of propulsion systems and turbomachinery. Prior to commencing his doctoral studies at the MIT GTL, Dr. Shah also worked at Pratt & Whitney in Connecticut. He is an active member of the AIAA and ASME, and is an Associate Fellow of AIAA and a recipient of the 2016 ASME IGTI John P. Davis award.