Effect of Quenching Kinetics on Unsteady Response of Pressure-Sensitive Paint

Pressure-sensitive paints (PSP) have recently been extended to high-frequency flowfields. Paint formulations have been used effectively to characterize pressure fluctuations on the order of 100 kHz. As the limits of PSP are extended, various experimental results indicate that the unsteady response characteristics are nonlinear. A thorough understanding of the photophysical mechanisms in paint response is needed. Gas transport properties, coupled with the nonlinear nature of the Stern‐Volmer relationship have an effect on the paint response. This work discusses the full implications of a diffusion-based model for the unsteady response of pressure-sensitive paint. Based on this model, it is shown that the indicated pressure response of PSP is faster for a decrease in pressure, and slower for a pressure increase. Effects of other factors, such as pressure-jump magnitude, pressure-jump range, and Stern‐Volmer nonlinearity, are evaluated. Furthermore, a fluidic oscillator is used to demonstrate experimentally the quenching kinetics of two types of PSP—polymer/ceramic and fast FIB. Results from the oscillator operated with argon, nitrogen, and oxygen gases at 1.59 kHz demonstrate behavior that agrees with the diffusion model. The polymer/ceramic PSP exhibited no delay between different test gases, indicating a flat frequency response of at least 1.59 kHz. Fast FIB, on the other hand, demonstrated a significant delay in rise time between the nitrogen and oxygen cases. Both the diffusion model and the experimental results demonstrate that the different responses to nitrogen and oxygen only become critical when the period of the flowfield oscillations is shorter than the response time of the paint formulation.