The 20-Inch Supersonic Wind Tunnel (SWT) is a versatile blow-down facility capable of producing supersonic Mach numbers from 1.6 to 5.0 and subsonic Mach numbers from 0.35 to 0.75. The rectangular test section is 20 inches high and 18 inches wide with optical access on three sides. The tunnel has a unique injection/projection support system for high-speed sting mounted models or models can be mounted on the floor or sidewall. Airfoil testing at subsonic speeds and very low Reynolds numbers is accomplished by using the tunnel’s low Mach capability. Depending on conditions, the run times typically range from approximately 30 to 900 seconds. Due to the large capacity vacuum system at LaRC, very low unit Reynolds numbers can be obtained with low stagnation pressures of approximately 0.5 psia at supersonic conditions and 0.2 psia at subsonic conditions. Higher Reynolds numbers are possible at stagnation pressures up to 130 psia for Mach numbers above 2.85. The maximum system mass flow rate of 280 lbm per second limits the maximum Reynolds number for Mach numbers below 2.85.
Typical test techniques available in the SWT include pressure (both dynamic and static), pressure sensitive paint, heat transfer, force/moment, and Schlieren. The ability to seed the flow allows a broad array of laser-based measurement techniques to be used. The facility also has a diagonal probe traverse allowing more conventional, but limited off-body measurements. The 24-inch diameter Schlieren system is used for basic visualization at supersonic speeds. For transition detection, hot-wires, films, and sublimating chemicals have been used. Video coverage of the test section and live-Schlieren with video recording are available.