Originally constructed in NASA Langley Field, the Virginia tech Stability Wind Tunnel has moved from stability derivative testing in the 1940’s to being the state-of-the-art facility for aeroacoustic testing, in particular for wind turbine blade development. The facility now and attracts millions of dollars in research from world leaders in wind turbine technology and other areas.
The facility is characterized by its large test-section (1.8m x 1.8m cross-section, 7.3m in length) and excellent flow quality (turbulence intensity is less than 0.05% at 80m/s). In 2006, these features motivated the addition of a novel anechoic configuration (invented at Virginia Tech by Drs. Devenport and Burdisso) where the test-section side walls are replaced by stretched Kevlar fabric. Any sound coming from the test-section will pass through the Kevlar window virtually unchanged (since the Kevlar is a porous fabric) and into the acoustic chambers (large empty rooms lined with foam wedges that eliminate noise reflections above 140Hz) on either side of the test-section. The Kevlar also creates a boundary (both porous and flexible) for the flow resulting in extremely good aerodynamic properties. This configuration therefore provides clear advantages over the typical open-jet configuration used traditionally for aero-acoustic facilities (where testing conditions are limited by the flow quality and deflection of the free jet).
For the past 6 years, these unique aerodynamic and acoustic capabilities have made the facility particularly attractive to the leaders (US and worldwide) in the wind turbine industry since it is the only wind tunnel in the world that can aero-acoustically test wind turbine blade sections near full scale conditions. Through self-financing and industrial support, the facility has developed a vast array of measurement techniques and instrumentation that include among others: over 500 channels of pressure scanning, computerized turntable, 120 channel high speed traversing rake (that can measure the pressure distribution across the entire span and width of the test-section), infra-red thermography for airfoil transition detection, Doppler Global Velocimetry for airfoil boundary layer measurements (with collaboration from Dr. Todd Lowe), and more recently a 117-microphone phased array for acoustic measurements. A 250-microphone phased array is also currently under development.
Due to its position within the university, the Stability Wind Tunnel mission is to offer these unique capabilities to academic researchers as well as undergraduate education. Every year, over 400 undergraduate students from 3 different departments (AOE, Mechanical Engineering, and Biomedical Engineering and Mechanics) get to use the facility as part of their undergraduate labs or student team work (senior design, Design-Build-Fly, Formula SAE etc…), giving them a truly unique opportunity to experience working in a state-of-the-art world-leading test facility.
The Stability Wind Tunnel is also the focus of the recently formed Center for Renewable Energy and Aerodynamics Testing (CREATe). The vision of the Center is to exploit the synergy between scientific advances in aerodynamics and acoustics, and engineering advances in renewable energy. The center was officially chartered by the university. It brings together 7 core faculty in Aerospace and Ocean Engineering and Mechanical Engineering and 11 affiliate faculty in a range of departments. The Center’s administrative home is in 660 McBryde Hall.