| Popis: |
Particle image velocimetry (PIV) is utilized with solid carbon dioxide (CO2) seeding material to conduct boundary layer measurements in the test section of the Air Force Research Laboratory?s Trisonic Gas-dynamics Facility (TGF), which has a 24 inch by 24 inch cross-section. Freestream velocity was set at Mach 0.3, Mach 0.5, or Mach 0.8 while stagnation pressure ranged from 500 to 2400 pounds per square foot (psf). High pressure liquid CO2 was directed through expansion nozzles into shroud tubes which led to solidified particles in the wind tunnel stagnation chamber. Two different sets of shroud tubes were used to modify the size of dry ice particles produced and the particle number density. Shroud tubes with an inside diameter (ID) of 0.824 inches provided good particle count and coverage for stagnation pressures between 500 and 1500 psf, while 0.364 inch ID shroud tubes demonstrated good particle count and coverage for stagnation pressures over 1000 psf. Overall, the PIV results produced freestream velocity measurements and boundary layer profiles which compared well with expected values. After initial processing, turbulence data closely followed trends expected within boundary layer, but levels were somewhat higher than anticipated. When the PIV data was processed using elliptical interrogation regions, elongated in the streamwise direction, resulting turbulence levels were much closer to expectations. |
