Particle Size Control for PIV Seeding Using Dry Ice
48th AIAA Aerospace Sciences Meeting Including the New Horizons Forum and Aerospace Exposition
Particle image velocimetry (PIV) has been carried out using solid carbon dioxide (CO 2 ) particles as the seed material to continue the development of clean seeding for use in large-scale, closed-circuit tunnels. Testing occurred in two wind tunnels at subsonic and supersonic speeds using dry ice particles generated by allowing liquefied CO 2 to expand from a small diameter injector tube through a larger diameter shroud tube. The particles were injected into the plenum and discrete solid
... screte solid particles, suitable for PIV measurements, were present in the test section. Data on particle size were first collected using a Malvern particle size analyzer for three sizes of injector tubes, two sizes of shroud tubes, and two different types of shroud tubes: a simple tube and a static mixing tube. The injectors using the static mixing shroud tube and the simple shroud tube were each used in the adjustable throat supersonic blowdown wind tunnel at the Air Force Institute of Technology with a 6 inch by 6.5 inch cross section. Particle size results for these two configurations suggested that the static mixing shroud tube decreased the Sauter mean particle diameter by a factor of three. In the tunnel, Mach 1.92 flow over a 10 • ramp was produced and PIV images captured particles above the ramp both upstream and downstream of the oblique shock while schlieren imaging provided insight into the flow conditions. Both the velocities far upstream and far downstream of the shock closely matched expectations, based on the wind tunnel instrumentation. Particle lag for the flow across the shock was quantified for the two cases, and despite the substantial, quantified differences in particle size measured at the shroud tube exit, the results for both shroud tubes were generally consistent with a theoretical response of a 2 µm particle. Finally, for the first time particles were injected into the stilling chamber of the Air Force Research Laboratory's closed-circuit Trisonic Gas-dynamics Facilty, which has a 24 inch by 24 inch cross-section at three subsonic speeds and four stagnation pressures. PIV was successfully carried out in each case. Measured streamwise velocities matched expected velocities within a few percent based on tunnel instrumentation, and iv freestream turbulence was found to be less than 2% in most cases. These results suggest that PIV using CO 2 particles may be robustly implemented in this closed-circuit wind tunnel without risk of contaminating the tunnel. v First and foremost, I would like to thank my advisor Dr. Mark Reeder for his unwavering support and endless patience. Thank you for giving me the freedom to explore while providing clear guidance throughout this endeavor. I'd also like to thank Mr.