Flow Patterns and Heat Transfer in a Cylindrical Annulus under 1g and low-g Conditions: Theory and Simulation

Abstract

A dielectric fluid is confined in a stationary vertical cylindrical annulus. A temperature difference is applied between the two cylinders, as well as an alternating electric potential. This configuration creates an active force called dielectrophoretic force, which acts as a thermal buoyancy force. Different axial gravity intensities are considered, so that two thermal buoyancies will affect the flow: the thermoelectric buoyancy intervenes in the radial direction and the Archimedean buoyancy acts in the axial direction. Linear stability analysis and direct numerical simulation are performed following experimental research that has been performed during parabolic flight campaigns.

Dielectrophoretic force-driven convection in annular geometry under Earth’s gravity

“…Meyer et al (2017) reported the flow after the first transition is axially aligned and consists of stationary columnar modes. Meier et al (2018) demonstrated experimentally the existence of those columnar modes for a few tuple of (∆T, V 0 ).…”

“…Visualisation of the flow of cell with aspect ratio Γ = 20 is realised with the shadowgraph method (Merzkirch, 1987;Schöpf et al, 1996;Meyer et al, 2017;Meyer, 2017;Meier et al, 2018). Shadowgraph is a very simple technique and provides flow visualisation of very high quality.…”

“…This section briefly describes the laboratory experiment. A detailed description is written in Meyer et al (2017) and Meier et al (2018). The experiment consists of two concentric axially aligned cylinders (see figure 1).…”

“…Heating of the inner cylinder is realised by pumping silicone oil Elbesil B5 via in/outlets into the inner cylinder. For experiments with the shadowgraph method applied we heat and cool with a custom-built technique very detailed described in Meyer et al (2017) and Meier et al (2018). For experiments using particle image velocimetry, we heat and cool with two thermostats.…”

“…Thus the dielectrophoretic (DEP) force has been remained in focus up to now, e.g. very recently in Laohalertdecha et al (2007); Marucho and Campo (2013); Dahley (2014); Travnikov et al (2015Travnikov et al ( , 2016; Futterer et al (2016); Meyer et al (2017Meyer et al ( , 2018; Meier et al (2018); Zaussinger et al (2018). The dielectrophoretic force depends on E 2 instead of E and is therefore independent of the direction of E. If the frequency of the electric potential Φ is high enough it can be time-averaged over a period of the electric field.…”