1. Mechanical and Aerospace Engineering
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

2. 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

3. 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

4. Experimental setup

5. Experimental setup

6. Experimental procedure
Sets of images
Ambient light
White field
Dot card
Iodine cell calibration
Jet images

7. Iodine cell calibration
4.4 V
4.3 V
4.2 V

8. Uneven seeding
Unfiltered image
Transmission image

9. Results

10. 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

11. 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

12. 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.

13. The End