caa a22 4500 606198857 CHVBK 20210128100935.0 cr unu---uuuuu 210128e20150201xx s 000 0 eng 10.1007/s00348-015-1905-y doi (NATIONALLICENCE)springer-10.1007/s00348-015-1905-y Differential infrared thermography for boundary layer transition detection on pitching rotor blade models [Elektronische Daten] [Markus Raffel, Christoph Merz, Till Schwermer, Kai Richter] Differential infrared thermography (DIT) was investigated and applied for the detection of unsteady boundary layer transition locations on a pitching airfoil and on a rotating blade under cyclic pitch. DIT is based on image intensity differences between two successively recorded infrared images. The images were recorded with a high framing rate infrared camera. A pitching NACA0012 airfoil served as the first test object. The recorded images were used in order to investigate and to further improve evaluation strategies for periodically moving boundary layer transition lines. The measurement results are compared with the results of unsteady CFD simulations based on the DLR-TAU code. DIT was then used for the first time for the optical measurement of unsteady transition locations on helicopter rotor blade models under cyclic pitch and rotation. Image de-rotation for tracking the blade was employed using a rotating mirror to increase exposure time without causing motion blur. The paper describes the challenges that occurred during the recording and evaluation of the data in detail. However, the results were found to be encouraging to further improve the method toward the measurement of unsteady boundary layer transition lines on helicopter rotor models in forward flight. Springer-Verlag Berlin Heidelberg, 2015 Raffel Markus Institute of Aerodynamics and Flow Technology, German Aerospace Center, Göttingen, Germany aut Merz Christoph Institute of Aerodynamics and Flow Technology, German Aerospace Center, Göttingen, Germany aut Schwermer Till Institute of Aerodynamics and Flow Technology, German Aerospace Center, Göttingen, Germany aut Richter Kai Institute of Aerodynamics and Flow Technology, German Aerospace Center, Göttingen, Germany aut Experiments in Fluids Springer Berlin Heidelberg 56/2(2015-02-01), 1-13 0723-4864 56:2<1 2015 56 348 https://doi.org/10.1007/s00348-015-1905-y text/html Onlinezugriff via DOI BK010053 XK010053 XK010000 Metadata rights reserved Springer special CC-BY-NC licence nationallicence 1 research-article jats NATIONALLICENCE NATIONALLICENCE NL-springer NATIONALLICENCE 856 40 https://doi.org/10.1007/s00348-015-1905-y text/html Onlinezugriff via DOI NATIONALLICENCE 700 1- Raffel Markus Institute of Aerodynamics and Flow Technology, German Aerospace Center, Göttingen, Germany aut NATIONALLICENCE 700 1- Merz Christoph Institute of Aerodynamics and Flow Technology, German Aerospace Center, Göttingen, Germany aut NATIONALLICENCE 700 1- Schwermer Till Institute of Aerodynamics and Flow Technology, German Aerospace Center, Göttingen, Germany aut NATIONALLICENCE 700 1- Richter Kai Institute of Aerodynamics and Flow Technology, German Aerospace Center, Göttingen, Germany aut NATIONALLICENCE 773 0- Experiments in Fluids Springer Berlin Heidelberg 56/2(2015-02-01), 1-13 0723-4864 56:2<1 2015 56 348