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Filtered Rayleigh Scattering Velocimetry - Accuracy Investigation in a M=2.22 Axisymmetric Jet. Jonas Gustavsson Corin Segal Mechanical and Aerospace Engineering University of Florida. January 2004. Purpose of study.
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Filtered Rayleigh Scattering Velocimetry - Accuracy Investigation in a M=2.22 Axisymmetric Jet Jonas Gustavsson Corin Segal Mechanical and Aerospace Engineering University of Florida January 2004
Purpose of study • Measure the accuracy of FRS for high-speed flow velocimetry in a realistic flow situation • Identify and quantify dominating sources of uncertainty • Propose ways of reducing total uncertainty
Experimental setup Axisymmetric Ø11 mm M=2.2 Free jet • Well-known flow with suitable Mach number range • No optical access issues • Comparison to pressure probe surveys possible • current setup • Eggers 1966 Pitot survey
Experimental procedure Sets of images • Ambient light • White field • Dot card • Iodine cell calibration • Jet images
Iodine cell calibration 4.4 V 4.3 V 4.2 V
Uneven seeding Unfiltered image Transmission image
Uncertainty sources • Laser drift 3h 35 m/s • Image overlap 0.15 pixels 10 m/s • Shot noise 10 m/s • Finite spectral width 10 m/s Total uncertainty: 40 m/s
Conclusions • FRS is a viable velocity measurement technique in a practical flow situation • Water vapor condensation limits light collection shot noise, but droplets track flow well • Laser drift dominates, but several sources contribute O(10 m/s) • Total estimated error ±40 m/s agrees well with experimental data
Future work • Improve the accuracy through better laser wavelength control. • Develop methods for analyzing data from FRS in unevenly, moderately seeded flows. • Assess FRS for simultaneous measurement of velocity and temperature in high-speed combustion flows.