Filtered Rayleigh Scattering Velocimetry - Accuracy Investigation in a M=2.22 Axisymmetric Jet
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Transcript of Filtered Rayleigh Scattering Velocimetry - Accuracy Investigation in a M=2.22 Axisymmetric Jet
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 setupEggers 1966 Pitot survey
Experimental setup
Experimental setup
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
Results
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.
The End