Measurement of heat transfer and shock/boundary-layer interaction in a transonic low-pressure turbine cascade using unsteady temperature-sensitive paint

Shock/boundary-layer interactions (SBLI) strongly influence the aerodynamic performance, heat transfer, and loss generation of transonic turbine cascades. The present study demonstrates the application of ultra-fast-response temperature-sensitive paint (TSP) for simultaneous characterization of the shock’s foot print on the suction surface and the surface heat transfer coefficient on a transonic low-pressure turbine cascade. Experiments were performed in the High-Speed Cascade Wind Tunnel (HGK) of the University of the Bundeswehr Munich under low-pressure transonic conditions. A Ru(phen)-based TSP applied on a carbon nanotube heating layer provided fast temporal response, enabling high-speed measurements at 16 kHz frame rate. The time-resolved temperature fields allow the identification of the shock footprint and its dynamic motion. A spectral analysis demonstrates coherent low-frequency shock oscillations that coincide with localized variations in surface heat transfer. The resulting heat transfer coefficient distributions capture the influence of the SBLI and associated changes in boundary-layer behavior with high spatial resolution. The results demonstrate that ultrafast-response TSP is a powerful non-intrusive diagnostic for the simultaneous investigation of unsteady aerodynamic and thermal phenomena in transonic turbomachinery. The presented methodology provides a valuable experimental tool for studying coupled shock dynamics and heat transfer and offers new opportunities for the validation of high-fidelity numerical simulations.