Development of a two-component PSP for short-duration hypervelocity wind tunnels

Abstract

Pressure-Sensitive Paint (PSP) has become an established optical measurement technique in aerodynamics due to its ability to deliver quantitative, spatially resolved surface pressure data. However, conventional PSP formulations are limited in high-speed applications, particularly in hypersonic facilities, where large and rapid changes in surface temperature and pressure occur. To address these challenges, a two-component PSP based on Pt(II) meso-Tetra(pentafluorophenyl)porphine (PtTFFP) is being developed through a collaboration between the German Aerospace Center (DLR), the University of Notre Dame (USA), and the Aichi Institute of Technology (AIT, Japan). Complementary measurements were performed at the National Research Council (NRC, Canada) in their acoustic resonance tube. The approach makes use of a temperature-referencing component to account for the inherent temperature sensitivity of the paint, thus improving pressure measurement accuracy under these demanding flow conditions. A first pilot study was performed in a cold-flow hypersonic Ludwieg-tube designed for the evaluation and testing of optical measurement techniques. Tests on a simple wedge model demonstrated the usability of this PSP formulation, whereby spatially-resolved pressure distributions in both streamwise and spanwise directions could be measured. These results highlight a key advantage of PSP over flush-mounted pressure transducers: the capability to obtain 2D image-based surface pressure fields. Several findings related to PSP performance and optical setup could be obtained, providing guidance for further optimization of the technique for use in hot flows. The ongoing and further development aims at providing the means to enable reliable PSP measurements in shock tunnels, with the particular focus being on future deployment in the High Enthalpy Shock Tunnel Göttingen (HEG).