Unsteady Boundary Layer Transition Measurements with Infrared Thermography

Development of Improved Measurement Schemes

By Mertens, Christoph (TU Delft Aerospace Engineering)

Abstract

TU Delft Aerospace Engineering
Flight experiments with two helicopters for unsteady boundary layer transition measurements on the main rotor of the EC 135, conducted at DLR Braunschweig in June 2018
(Image: TU Delft Aerospace Engineering)

Online  —  The boundary layer transition location is a crucial design parameter in aerodynamics. The computational prediction of boundary layer transition in engineering applications is typically based on empirical models.

These models require experimental measurements for calibration and validation purposes. For unsteady aerodynamic processes, the range of suitable boundary layer transition measurement techniques is traditionally limited to fast-response discrete sensor techniques, e.g. hot-film anemometry.

Introduced in 2014, differential infrared thermography is an alternative approach to measuring unsteady boundary layer transition using thermal images acquired with an infrared camera.

The application of this optical measurement technique reduces the experimental effort, but problems emerge when the temperature response of the surface under investigation is slower than the aerodynamic unsteadiness.The idea of differential infrared thermography is to evade this problem by subtracting subsequent thermographs and accrediting the largest difference to the moving boundary layer transition location.

Read the full abstract and download the full article at: https://repository.tudelft.nl/islandora/object/uuid%3Ac9ef5823-c258-4c11-82b3-b7aaae78fa7d

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