Application of lifetime PSP imaging method to a cryogenic wind tunnel

The intensity-based method is a most common technique to convert Pressure-Sensitive Paint (PSP) images to surface pressure. However, this method is not suitable for a cryogenic wind tunnel because the thermal equilibrium condition cannot be achieved when the tunnel is stopped to take the wind-off reference image. In the present study, we applied the lifetimebased PSP imaging method to a cryogenic wind tunnel. Using this method, surface pressure can be calculated from two images obtained at the wind-on condition. In this experiment, a circular-arc bump model coated with PtTFPP/PTMSP paint was tested in the JAXA 0.1-m Cryogenic Transonic Wind Tunnel and PSP images were acquired using a UV-LED pulse illuminator and a multi-gated CCD camera. As a result, we succeeded in visualizing surface pressure distribution induced by a shock wave on the model by using lifetime imaging technique. However, nonnegligible deviation from pressure tap data was observed for the lifetime-based PSP data in the region of the model leading- and trailing- edges. Also the lifetime-based PSP data showed relatively rapid deterioration. These anomalies were not observed in the intensity-based PSP data in the same experiment. To use lifetime PSP imaging method for quantitative pressure measurement, photo-physical mechanism behind these anomalies should be clarified.