Dynamic modeling and compensation schemes for pressure sensitive paints in unsteady flows

Pressure sensitive paints (PSP) have been used extensively in the past decade to measure surface pressures in steady flow conditions. There are many unsteady phenomena to which the aerospace community would like to apply PSP as a measurement technique. However, to date there has not been a viable model to describe the dynamic behavior of the PSP system. A rigorous development from a systems dynamics perspective is needed to advance PSP from a static measurement technique to a dynamic one.; With this aim, two models for the dynamic behavior of pressure sensitive paints will be presented. The first of the two models is a purely empirical approach to designing a model and compensator. The second model encompasses the physics of the process by which an unsteady pressure field over the paint layer affects the layer and causes an intensity of fluorescence that is fluctuating in time. Within this second model, two different forms for the static calibration are chosen. The first results in purely linear system dynamics whereas the second yields a nonlinear system. These models are then compared to experimental data. Next, a dynamic compensation scheme is developed to correct for the time-lag and amplitude-damping behavior of the paint. Finally, the compensation scheme is applied to PSP data taken surrounding an unsteady (periodic) jet injected transversely into a Mach 1.56 freestream.