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The objective of this paper is to establish the validity of a measurement apparatus for determining aerodynamic drag caused by acoustic liners. Conventional acoustic liners for ducted turbofan engine nacelles have been proven to reliably reduce engine noise in commercial aircraft for a narrow frequency range. Traditional acoustic liners consist of a porous facesheet, honeycomb core, and solid backing. As technology has developed, new liner designs, including variable-depth cores, show promise of reducing noise in a broad frequency range. Additionally, the next generation of aircraft design may allow for additional aircraft surface area to be covered by acoustic liners, further reducing aircraft noise perceived on the ground. Before these advanced acoustic technologies can make their way onto commercial aircraft fleets, the aerodynamic drag caused by the liners must be understood. Using the Mach 0.6 Wind Tunnel at the University of Notre Dame, a direct drag measurement system has been developed utilizing a linear force balance. In combination with indirect drag measurements taken at NASA Langley’s Curved Duct Test Rig, measurement confidence has been established. This paper will detail the capabilities of the direct drag measurement system at Notre Dame and explore its intended future use in developing new liner technologies.
Christopher Jasinski (Fri,) studied this question.