Formulation of pressure sensitive paints for unsteady measurements

One of the main part of Pressure Sensitive Paint (PSP) activity at Onera is devoted to the application of this technique to unsteady measurements. In order to reduce the response time to a few milliseconds, new paints have been developed. The coating we have developed consists of a pyrene derivative covalently linked to silica particles. The grafted silica is mixed with a water soluble alumina and can be sprayed with an airbrush. This paint emits fluorescence when it is excited at 340 nm and its pressure sensitivity is around 90%/bar. An aging test that consists in heating the coating at 60/spl deg/C at a pressure of 200 mbar for one hour results in no decrease of the emitted intensity. The response time of this paint, defined as the time required to reach 99% of the maximum intensity level, is less than 5 ms.