Crossflow investigation with Temperature-Sensitive Paint in low-speed wind tunnels

Kurzfassung

The Temperature-Sensitive Paint (TSP) method is a thermographic measurement technique and mainly used to do flow visualizations, but also quantitative temperature, heat transfer and skin friction measurements are possible. To perform flow visualizations in low speed facilities the contrast needs to be enhanced by generating a heat flux between model and fluid. This way the measurement relies on the spatial variation of the heat transfer coefficient, which depends on the local skin friction coefficient (Reynolds analogy). Therefore, the department of Experimental Methods at DLR Göttingen develops a combination of Temperature-Sensitive Paints and electrical-heating methods for the application in lowspeed and high-speed wind tunnels (ambient and cryogenic Temperatures) and water facilities. The application of the TSP method in two different wind tunnel campaigns investigating crossflow instability is shown. One model is a natural laminar flow (NLF) wing and the other is the "Redesigned swept flat-plate experiment for crossflow-induced transition studies", which was in its flrst setup designed by H. Bippes and coworkers. In both measurements the TSP technique was successfully used to visualize the footprint of the stationary crossflow vortices and the laminar-turbulent transition. Further data analysis exceeding the pure flow visualization is discussed.