This paper describes experiments conducted to evaluate the use of optical sensors to measure pressure distributions on an aircraft wing. Wind tunnel tests were performed on a model wing equipped with optical and conventional pressure sensors. The results show that optical sensors can provide accurate pressure readings if temperature corrections are applied to account for each sensor's temperature sensitivity. With proper calibration and a high enough sampling rate, optical sensors were found to be a viable alternative to other pressure measurement techniques for studying boundary layer transition on aircraft wings.

1. AIAA-2009-5661 Temperature Variation of Optical Sensors Popov and R. Botez, École de Technologie Supérieure, Montréal, Canada; M. Mamou, National Research Council of Canada, Ottawa, Canada; and L. Grigorie, École de Technologie Supérieure, Montréal, Canada AIAA Guidance, Navigation, and Control Conference 10 - 13 Aug 2009 Place, Chicago, Illinois

5. Experimental setup Optical sensor Kulite sensor Kulite OS 1 OS 2 OS 3 OS 4 Oil film flow visualization

7. Optical sensors reading correction Δ T is the difference between the temperature calculated at the sensor location and the temperature of the calibration from the beginning of test 296 K Local mach no. Local temperature Total temperature of air in wind tunnel Pressure correction where and Optical Sensor no. Channel no. Temperature deviation Reading deviation OS1 2 0.037 psi/deg C - 1.11% of mean pressure psi OS2 4, 6 0.030 psi/deg C - 0.65% of mean pressure psi OS3 12, 14 0.037 psi/deg C - 1.02% of mean pressure psi OS4 16, 18 0.026 psi/deg C - 0.62% of mean pressure psi

8. Pressure distribution correction

9. Spectral analysis of optical sensors signal Laminar-to-turbulent transition triggered by Tolmien- Schlichting waves f>1kHz Optical sensors blind to detect transition due to sampling rate limitation Other optical sensors tested were temp. compensated f=10 kHz F.S. 15 psia Accuracy 1% (0.15 psi) Resolution 0.1% (0.015 psi) Not sufficient accuracy and resolution Kulite sensors Sampling at 10 kHz Resolution <0.002 psi Mach = 0.275 Tolmien- Schlichting waves PT8 OS4 Mach = 0.2 PT8 OS4 Mach = 0.1

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