Lockheed Martin Low Speed Wind Tunnel Acoustic Upgrade

Paper #:
  • 2018-01-0749

Published:
  • 2018-04-03
Affiliated:
Abstract:
The Lockheed Martin Low Speed Wind Tunnel (LSWT) was brought into service in Marietta, Georgia in 1967. Since then, this facility has provided aerodynamics testing capabilities for product development in the aviation and automotive fields. The LSWT features a closed-return airline with two solid wall test sections, the smaller of which has a cross-section area of 375 square feet and a maximum wind speed of 200 mph. This test section is called the low speed test section. The LSWT was upgraded over a six month period in 2016. This upgrade included replacing all four sets of turning vanes with acoustic turning vanes, adding acoustic treatment to the side walls and ceiling to portions of the airline circuit and replacing the fan protection and stilling chamber screens. The wooden side wall and ceiling surfaces in the low speed test section were replaced with acoustically treated walls. The LSWT upgrade reduced the background noise levels and provided an acoustically absorbent environment in the low speed test section during wind tunnel operation. This was achieved while maintaining the pre-upgrade aerodynamic flow quality of the LSWT. The most technically challenging aspect of the LSWT acoustic upgrade was to provide acoustically absorbent test section surfaces that would not generate excessive wind noise. Acoustically treated wall surfaces must be transparent to incoming sound waves in order for those waves to penetrate the wall surface and be absorbed by the acoustic treatment, such as mineral wool or fiberglass batts. Therefore, a typical surface material for acoustically treated walls is porous sheet metal. However, porous sheet produces large amounts of noise when subjected to wind. A new surface material was developed consisting of a fine wire cloth diffusion bonded to a porous plate in order to satisfy both acoustic transparency and low wind noise requirements. This paper describes the details of the LSWT acoustic upgrade and the aerodynamic and acoustic testing that was performed prior to and after the upgrade.
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