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Towards Quantitative Wall Shear Stress Measurements: Considering the Flow Behavior of Liquid Crystals

Melekidis, Stefanos ORCID iD icon 1; Ebert, Marcus; Schmid, Jonas 1; Bauer, Hans-Jörg 1
1 Institut für Thermische Strömungsmaschinen (ITS), Karlsruher Institut für Technologie (KIT)

Abstract (englisch):

Liquid crystal diagnostics is a capable tool for determining quantitative wall shear stress distributions with high spatial resolution, which may be applied to almost any surface shape. To determine a wall shear stress vector field, the state-of-the-art calibration procedure requires taking multiple images of the liquid crystal-coated surface from different points of view. In the literature, it is reported that this data acquisition is usually performed using multiple, up to six, commercially available consumer cameras to synchronously record the liquid crystal signal. However, the need for multiple recording devices makes measurement diagnostics unsuitable even for laboratory measurements, as often only one (identical) camera is available. Using a single camera results in a different wall shear stress vector field due to the time-dependent liquid crystal signal, which results from the time offset between the individual exposures compared to the synchronous exposures under otherwise identical boundary conditions. This time dependence follows from the thixotropic behavior of the liquid crystals. On top of that, two other effects, one of which is not described in the literature, affect the liquid crystal color signal. ... mehr

Postprint §
DOI: 10.5445/IR/1000148506
Frei zugänglich ab 01.10.2023
Zugehörige Institution(en) am KIT Institut für Thermische Strömungsmaschinen (ITS)
Publikationstyp Proceedingsbeitrag
Publikationsmonat/-jahr 09.2022
Sprache Englisch
Identifikator KITopen-ID: 1000148506
Erschienen in 25th Conference of the International Society for Air Breathing Engines
Veranstaltung 25th Conference of the International Society for Air Breathing Engines (ISABE 2022), Ottawa, Kanada, 25.09.2022 – 30.09.2022
Schlagwörter liquid crystals, wall shear stress, flow behavior, thixotropy, temperature dependence, calibration, experimental data, consumer camera
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