Overview of the self-illumination effect applied to pressure sensitive paint applications

The so-called "Self-Illumination Effect" (SI) is described. Its appears when using luminescent paints like PSP. Correcting SI requires to address several problems: the paint emission model, the paint reflection model and the design of an appropriate algorithm. The emission and reflection models of a pyren-based paint are described. It comes out that the simplest model, which is the Lambertian model, matches quite well the calibration measurements made with a BRDF calibration rig. An algorithm has been implemented in the Onera's PSP software. It includes a new approach to decrease the size of the problem, which is based on the segmentation of the image in triangles. The algorithm handles the occlusions and can be used for wind-tunnel applications with an acceptable time penalty. It has been extended for real paint models. It provides a significant accuracy improvement, which is small compared to the computational effort. This leads to check the benefit of using a real model, especially for PSP applications, where the intensity method compensates for remaining errors.