A Grazing Flow Impedance Facility For Engine Nacelle Acoustic Liners

Acoustic liners remain the standard for providing a method to reduce environmental noise from aircraft engine nacelles. To aid in their development, facilities are required that are capable of accurately educing the acoustic impedance in the presence of mean flow. The Grazing Impedance Tube at NASA LaRC possesses these capabilities and was donated to the University of Florida. Improvements have been made to enable optical flow diagnostics, provide an increased speed range, and reduce turbulence levels. This facility provides a testbed to improve upon current liner impedance eduction methods as well as facilitate development of novel design approaches and studies into fundamental liner flow physics.

Grazing Flow Impedance Tube Profile

Metric Value
Dimensions 2" x 2"

Maximum Mach Number

Maximum SPL

130 dB @ Ma = 0.5

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