Heat transport in turbulent electro-hydrodynamics

<p>Electro-hydrodynamics (EHD) plays an important role in many industrial applications. Ink-jet printers, microwave drying facilities, and lab-on-a-chip devices utilize dielectric properties of the working fluids and their manipulation without moving parts. Another application is found in heat exchangers, where the dielectrophoretic force is used to increase heat transfer due to thermal buoyancy. In particular, the dielectrophoretic force has great advantages in low- and micro-gravity conditions since the force can be used to mimic a gravitational force field. Hence, convection in a rectangular cavity induced by EHD is a model system comparable to Rayleigh-Benard (RB) convection. However, the electric-driven buoyancy term and dielectric heating make the system more complex. The direction of the triggering dielectrophoretic force depends mainly on the temperature gradient which can be used to manipulate the heat flux or the entire structure of the convective flow. Layer formation, comparable to double-diffusive convection, and convective overshooting are two representative cases which can be established by EHD, too. We will present first results of turbulent convection induced by EHD in the rectangular cavity and the impact of volumetric heating. For this purpose, the Boussinesq approximation, as well as compressible models for EHD, are tested also for applicability in geophysical relevant regimes. This is a crucial point as the limitations by incompressible modeling are not well-understood for EHD. The main focus of the study is the analysis of the heat flux as a function of the thermo-electric feedback and the dielectric heating rate. Convective overshooting and layer formation are examined closely. Results of this study are used to estimate transport properties and time scales. Applications using EHD are the GeoFlow and AtmoFlow experiments. The GeoFlow experiment was conducted several years on the International Space Station and gained deep insight into EHD driven convection in the spherical shell geometry. The AtmoFlow experiment is under construction and is planned for operations on the ISS in 2024. This experiment is designed to study atmospheric like flows in the spherical shell.</p>