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Simultaneous PIV and shadowgraph measurements of thermo-electrohydrodynamic convection in a differentially heated annulus

Simultane Messung mit PIV und Shadowgraph von thermo-elektrohydrodynamischer Konvektion in einem differentiell beheizten Ringspalt
Peter S. B. Szabo ORCID logo, Antoine Meyer, Martin Meier, Vasyl Motuz, Yaraslau Sliavin and Christoph Egbers
From the journal tm - Technisches Messen

Abstract

Convection in a silicone oil with a temperature dependant fluid property is investigated experimentally in a differentially heated cylindrical annulus. A convective flow is induced by terrestrial gravity in axial direction and combined with an electrical tension applied between both cylinders to induce thermo-electrohydrodynamic convection. To capture the evolving velocity and temperature fields a novel combination of simultaneous PIV and shadowgraph technique is utilized. Results reveal azimuthal modes with cold and hot jets from inner and outer cylinder that are referred to the electric tension. The lack of information in the shadowgraph pictures were recovered by the PIV technique providing a deeper understanding in the nature of the development of the azimuthal mode number and the surrounding axial flow of natural convection. In addition, the results provide a robust framework in the capability of combining both techniques to investigate complex flow patterns that are non-axisymmetric.

Zusammenfassung

Die Strömung in einem Silikonöl mit temperaturabhängiger Fluideigenschaft wird experimentell in einem differentiell beheizten Ringspalt untersucht. Auftriebskonvektion wird durch die Erdgravitation in axialer Richtung induziert und mit einer dielektrophoretischen Kraft, die durch eine zwischen beiden Zylindern angelegte elektrische Spannung erzeugt wird, überlagert, um eine thermoelektrohydrodynamische Konvektion zu erzeugen. Um die sich entwickelnden Geschwindigkeits- und Temperaturfelder zu erfassen, wird eine Kombination aus simultan messender PIV- und Schattentechnik verwendet. Die Ergebnisse zeigen azimutale Moden mit kalten und heißen Bereichen, die zwischen beiden Zylindern stationär werden und auf die dielektrophoretische Kraft zurückzuführen sind. Die fehlenden Informationen aus den zweidimensionalen Schattenbildern können mittels der PIV-Technik vervollständigt werden. Erst die Kombination der beiden Techniken ermöglicht ein tieferes Verständnis der dreidimensionalen Strömungseigenschaften, der Entwicklung der azimutalen Modenzahl und der axialen Strömung der natürlichen Konvektion. Darüber hinaus zeigen die Ergebnisse die Fähigkeit der kombinierten Messmethoden komplexe Strömungsmuster zu untersuchen, die nicht achsensymmetrisch sind.

Funding source: Bundesministerium für Wirtschaft und Energie

Funding source: Deutsches Zentrum für Luft- und Raumfahrt

Award Identifier / Grant number: 50WM1944

Funding statement: The project ”Thermoelektrische Konvektion unter Schwerelosigkeit (TEKUS)” is supported by the BMWi via the space administration of the German Aerospace Center DLR under grant no. 50WM1944.

Acknowledgment

We acknowledge the support of the Centre Nationale d’Études Spatiales (CNES), Novespace S.A. in Bordeaux and our technical staff Stefan Rohark, Robin Stöbel and Tark Bista at Brandenburg University of Technology.

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Received: 2021-12-01
Accepted: 2021-12-21
Published Online: 2022-01-21
Published in Print: 2022-03-31

© 2022 Walter de Gruyter GmbH, Berlin/Boston