This is a Purchase Description for the procurement of a Closed-Circuit Wind Tunnel by the U.S. Army TMDE Activity (USATA). The Army requires one closed-circuit wind tunnel to be delivered to the Army Primary Standards Laboratory (APSL) at Building 5435, Redstone Arsenal, AL 35898. The wind tunnel will be used by Army Engineers and Technicians in conjunction with a Laser Doppler Velocimetry (LDV) system for air velocity measurements, enabling lower air speed measurement capabilities and reduced overall lab measurement uncertainty compared to current methods.
The wind tunnel must meet specific technical requirements: maximum operating speed of approximately 50 meters per second (~9,900 feet per minute); test section walls with 6.85 millimeter (0.27-inch) thick grooves at approximately 75 percent of total length for nozzle restriction plates; test section size of 101.6 by 101.6 millimeters (~4 by 4 inches); turbulence intensity less than 1 percent across the operating range; at least two sealable ports for instrument insertion accommodating various sizes (4.3 mm, 6.3 mm, 7.9 mm, 9.5 mm, 10.1 mm, 12.7 mm, and 15.9 mm diameters), with one port located 49.5 mm from the inlet and the other offset 37.5 mm; optical-quality glass sidewalls to minimize laser propagation interference; and a centrifugal fan design controlled by a variable-frequency drive (VFD) connected to a motor of appropriate size and power. Any submitted design must demonstrate compliance with specified air speed and turbulence requirements through quantitative analysis such as computational fluid dynamics (CFD) simulations or equivalent methods. The VFD interface must support computer software or manual control without relying on internet, Bluetooth, or WiFi connections, and must be programmable via National Instruments' LabVIEW software.
