Optimisation of Differential Infrared Thermography for Unsteady Boundary Layer Transition Measurement
C. Christian Wolf (Deutsches Zentrum für Luft- und Raumfahrt (DLR))
C. Mertens (TU Delft - Aerodynamics, Deutsches Zentrum für Luft- und Raumfahrt (DLR))
Anthony Gardner (Deutsches Zentrum für Luft- und Raumfahrt (DLR))
Christoph Dollinger (University of Bremen)
Andreas Fischer (University of Bremen)
More Info
expand_more
Other than for strictly personal use, it is not permitted to download, forward or distribute the text or part of it, without the consent of the author(s) and/or copyright holder(s), unless the work is under an open content license such as Creative Commons.
Abstract
Differential infrared thermography (DIT) is a method of analyzing infrared images to measure the unsteady motion of the laminar–turbulent transition of a boundary layer. It uses the subtraction of two infrared images taken with a short time delay. DIT is a new technique which already demonstrated its validity in
applications related to the unsteady aerodynamics of helicopter rotors in forward 2ight. The current study investigates a pitch–oscillating airfoil and proposes several optimizations of the original concept. These include the extension of DIT to steady test cases, a temperature compensation for long–term measurements,
and a discussion of the proper infrared image separation distance. The current results also provide a deeper insight into the working principles of the technique. The results compare well to reference data acquired by unsteady pressure transducers, but at least for the current setup DIT results in an additional measurement–related lag for relevant pitching frequencies.
help_outline