Application of Carbon Nanotubes (CNT) and Temperature-Sensitive Paint (TSP) for the Detection of Boundary Layer Transition

For aerodynamic profile tests on aircraft or wind mill models, transition detection is generally of great interest. Under ambient flow conditions the infrared technique (IR) is a well-established image-based method to carry this out. In high Reynolds number tests which are conducted at low temperatures or at high pressures the IR technique does not work very well whereas the Temperature-Sensitive Paint (TSP) technique is in principle well-suited to operate under these conditions. However, for the use of TSP at high pressures the feasibility has to be checked and some technical aspects have to be solved. Boundary layer transition detection by means of TSP generally requires an artificial temperature step to enhance the temperature difference between the laminar and turbulent boundary layers. This paper presents combination of TSP and Carbon Nanotubes (CNT) to generate a well-defined temperature step to detect laminar-turbulent transition. After pre-testing CNT and TSP in the laboratory, a wind tunnel experiment was conducted in the high pressure wind tunnel in Gottingen (DNW-HDG) for laminar-turbulent transition detection on a two-dimensional model for Re ≤ 8 Mio.