Discussion on mechanism of pressure-sensitive paints

The pressure-sensitive paint is very useful and easy way to obtain the pressure distribution on surfaces. Usually the pressure distribution by the paint shows good agreement with that obtained by other methods, like a pressure tap. Recently, the paint has been adopted to the high Knudsen number regime for pressure measurement, and showed possibility of pressure measurement for wide range of flows. The mechanism of the pressure-sensitive paint is mainly discussed within the luminescence intensity and the oxygen quenching of luminescent molecules. Still, it is unclear that the luminescence intensity is really proportional to the pressure, or another related value, especially in the high Knudsen number regime. Here, in this study, we tried to relate the flux and the pressure of oxygen to the luminescence intensity of the pressure-sensitive paint, and clear out the limit of application from the gas dynamical point of view.