Acoustic/drag interaction and its impact on future aircraft design

Abstract

For several decades, acoustic liner technology has substantially reduced the noise created by commercial jet engines. Conventional placement of the perforate-over-honeycomb liner is in the fore and aft bypass duct of an engine nacelle; however, future aircraft design may incorporate liners on additional surfaces, such as the underside of wings and the fuselage. In order to use liner technology in novel locations, the impact of the porous facesheet and core of the liner on the aerodynamic drag of the craft must be fully understood. Work conducted at the University of Notre Dame has experimentally evaluated this drag, as well as the impact of acoustic fields on the aerodynamic drag produced by acoustic liners. Measurements of several quantities across the full boundary layer profile show this impact is substantial and quantifiable. Such results for several liner facesheets will be presented. Through further testing of the acoustic impedance of various facesheets at the University of Hartford, the goal of striking design balance between acoustic performance and aerodynamic reliability can become more clear. Fluid mechanic, acoustic, and direct aerodynamic measurements for several liner samples will be presented and discussed.