Combination of Temperature-Sensitive Paint (TSP) and Carbon Nanotubes (CNT) for Transition Detection

Abstract

Boundary layer transition measurements on two wind tunnel models by means of Temperature-Sensitive Paint (TSP) in combination with Carbon Nanotubes (CNT) were performed in the high pressure wind tunnel DNW-HDG and in the cryogenic wind tunnel DNW-KKK. Both TSP and CNT can be applied by the airbrush technique to the wind tunnel models. No chemical or other interaction between CNT and TSP was observed. Therefore the CNT layer underneath the TSP layer could successfully be used to generate the required artificial temperature step dTau/dt°≈°1K/60 s for visualization of the laminar to turbulent transition on the wind tunnel model. Since the heating by CNT is very homogenous laminar-turbulent transition can already be seen in the raw images. Transition location change on the wind tunnel model as a function of Reynolds number and angle-of-attack are presented. By combination of TSP and CNT as a tool for transition detection measurements, the productivity of the data acquisition can be very much increased compared to the standard temperature step method (e.g. where the temperature of the test gas is varied) and no change in Reynolds number occurs, as would be the case when the gas temperature changes.