Surface pressure measurements by using pressure-sensitive paints

Until recently, wind tunnel measurements were made solely by pressure taps. But now an optical measurement method has been introduced and is replacing the usual instrumentation, at least for transonic wind tunnels: Pressure-Sensitive Paint, or PSP, which is a method generating an image of the pressure on the surface. The enthusiasm for this technique is prompted by the considerable savings it offers in terms of model instrumentation cost and model construction time, while the wealth of information that can be extracted from the images makes it a preferential investigation tool for complex flows. This article presents the basics of PSP and the way it is used. It is relatively simple to use, in fact, but requires many precautions if a high level of accuracy is desired. The software aspects are important, especially for tests conducted in an industrial context. The various elements of a PSP system are illustrated here with an example of application in low-speed testing. Advanced topics as model deformation are also discussed.