Yip - Development and Application of a High-Speed Three-Dimensional Density Measurement Technique for Aero-Optic Applications
Final rept. Apr 2008-Mar 2011
AUBURN UNIV AL DEPT OF AEROSPACE ENGINEERING
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A density measurement technique based on the planar laser induced fluorescence PLIF of acetone vapor was developed and shown to be practical for 2-D density measurements in a high speed wind transonic wind tunnel. The random uncertainty in density measurements was estimated to be on the order of 8 without pixel binning and as low as 3 with pixel binning, thus showing that acetone PLIF is a viable technique for measurement of density in compressible flow fields. The technique was applied to visualize the shock induced separation and turbulent wake of a hemisphere mounted in a Mach 0.78 free stream. Density images clearly showed the presence of shock waves, a flapping wake structure and significant density drops within the cores of vortices formed in the separating free shear layer. The density drops could reach magnitudes up to 50 from the free stream value confirming that compressibility effects on density fluctuations within a weakly compressible shear layer are significant and cannot be explained through mixing models alone.