Dual-luminophor pressure-sensitive paint: I. Ratio of reference to sensor giving a small temperature dependency

Pressure-sensitive paint (PSP) is playing an important role in aerodynamic testing. Its use provides a number of advantages over discrete pressure taps traditionally used on conventional wind tunnel models: (i) obtaining continuous quantitative pressure distributions over a surface; (ii) visualizing dynamic flow processes that measure areas not possible with conventional pressure taps (e.g. thin trailing edges); and (iii) real time modeling. The result is better integration of experimental and computational fluid dynamics leading to significant reductions in time for prototyping of new designs. The use of PSP relies on accurate measurement of changes in the paint’s luminescent intensity as a function of pressure change, which in turn requires careful monitoring and placement of light sources and pre-calibration of the PSP covered surface in “wind-off” conditions. Paint in-homogeneity and inconsistent surface illumination require exact registration of the calibration ‘wind-off’ image with subsequent ‘wind-on’ images for intensity change calculations to be meaningful. Model motion between ‘wind-on’ and ‘wind-off’ images leads to systematic errors that are hard to quantify. A dual-luminophor paint containing both a sensor and a reference luminophor molecule should alleviate these technical problems. This paper introduces such a dual-luminophor PSP made from our newly developed oxygen-sensitive molecule platinum tetra(pentafluorophenyl)porpholactone (PtTFPL), which provides Isen, and magnesium tetra(pentafluorophenyl)porphine (MgTFPP), which provides Iref as the pressure-independent reference. The ratio Iref/Isen in the FIB polymer produced ideal PSP measurements with a temperature dependency of −0.1%/°C.