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

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 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