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

## TL;DR

This study investigates the stability and flow structures of dielectric fluid convection driven by dielectrophoretic forces in an annular geometry under Earth's gravity, combining experiments and simulations to identify transition points and heat transfer enhancement.

## Contribution

It provides a comprehensive analysis of the stability and pattern formation in electro-hydrodynamic convection, validating linear stability predictions with experimental and numerical results.

## Key findings

- Transition from natural to electro-hydrodynamic convection identified
- Flow forms vertically aligned stationary columnar modes after transition
- Heat transfer is numerically shown to be enhanced

## Abstract

Context: A radial temperature gradient together with an inhomogeneous radial electric field gradient is applied to a dielectric fluid confined in a vertical cylindrical annulus inducing thermal electro-hydrodynamic convection. Aims: Identification of the stability of the flow and hence of the line of marginal stability separating stable laminar free (natural) convection from thermal electro-hydrodynamic convection, its flow structures, pattern formation and critical parameters. Methods: Combination of different measurement techniques, namely the shadowgraph method and particle image velocimetry, as well as numerical simulation are used to qualify/quantify the flow. Results: We identify the transition from stable laminar free convection to thermal electro-hydrodynamic convective flow in a wide range of Rayleigh number and electric potential. The line of marginal stability found confirms results from linear stability analysis. The flow after first transition forms a structure of vertically aligned stationary columnar modes. We experimentally confirm critical parameters resulting from linear stability analysis and we show numerically an enhancement of heat transfer.