Magnetic resonance imaging of flow and mass transfer in electrohydrodynamic liquid bridges

Abstract

Here we report on the feasibility and use of magnetic resonance imaging based methods to the study of electrohydrodynamic (EHD) liquid bridges. High speed tomographic recordings through the longitudinal axis of water bridges were used to characterize the mass transfer dynamics, mixing, and flow structure.By filling one beaker with heavy water and the other with light water it was possible to track the spread of the proton signal throughout the total liquid volume. The mixing kinetics are different depending on where the light nuclei are located and proceeds faster when the anolyte is light water. Distinct flow and mixing regions are identified in the fluid volumes and it is shown that the EHD flow at the electrodes can be counteracted by the density difference between water isotopes. MR phase contrast imaging reveals that within the bridge section two separate counter propagating flows pass one above the other in the bridge.

Armstrong Liquid Bridge: Formation, Evolution and Breakup

“…3b), and its bi-directionality is clearly shown by the thermal video (SV 3) and the mass transport in the beakers (more details in Appendix B). Specifically, the maximum velocity [20] is comparable with the maximum flow velocity in order of tens of millimeters per second (Fig. 9b).…”

“…Secondly, during the evolution stage, the bi-directional axial flow was observed using magnetic resonance imaging [20], and was explained by the electro-osmotic flow due to the charges on the outer surface of the liquid bridge [16].…”

Reversed Currents in Charged Liquid Bridges

“…As motivated by the recent visualizations of bidirectional flow [28], we have considered, in addition to bulk charges, a spatial modulation of the radial charge distribution such that a surface potential occurs. Solving the Navier-Stokes equation leads to a modified mass flow through the bridge.…”

“…Since both mass and charge transport are coupled, here we find the possibility that the mass transport might show a reverse behavior dependent on the parameters. This study is motivated by the bidirectional flow visualized recently in [28] and measured with mass and charge transfer in [29].…”

Electrically Induced Liquid–Liquid Phase Transition in a Floating Water Bridge Identified by Refractive Index Variations

“…Formal relationships between the physical fluid parameters, electric field intensity, and experimental configuration have been worked out by Marín and Lohse [7]. Later Morawetz [8][9][10] successfully modelled the bridge as a charged catenary, and his considerations concerning the flow profile match the experimental findings of Wexler et al [11]. Aerov [12], on the other hand, proposed a model where surface tension is responsible for holding the bridge against the gravity.…”