Enhanced Pressure-Sensitive Paint Implementation in Low-Speed Flow Applications

Abstract

The implementation of pressure-sensitive paint (PSP) in low-speed flow testing is challenging due to small pressure variations and low signal-to-noise ratio for PSP in such conditions. Achieving high luminescence intensity and high pressure sensitivity together helps in reducing uncertainty in PSP measurements. A PSP formulation with these attributes, metal-enhanced luminescence pressure-sensitive paint (MEL-PSP), was characterized by a priori calibration and implemented in low-speed flow experiments using intensity-based method to assess its performance. MEL-PSP exhibits a factor of two luminescence enhancement while maintaining a high pressure sensitivity in the pressure range for low-speed flows. MEL-PSP painted on a NACA 0012 airfoil (110 mm chord length) shows an average of 52.8% standard deviation reduction in pressure measurement compared with its conventional counterpart in low-speed flow condition (freestream velocity less than 25 m/s). While the chordwise pressure distribution obtained from MEL-PSP response shows trends in agreement with XFOIL simulation, offsets postulated to be caused partially by photodegradation and temperature induced errors were observed. While the standard deviation reduction indicates an improved precision of the MEL-PSP, this study confirms the multifaceted challenges in low-speed flow PSP imaging especially in achieving higher accuracy and precision simultaneously. The importance of thorough PSP development strategies and experimental designs was also observed, which must be implemented in the future development.