Numerical simulation of electro-conjugate fluid flow considering electric double layer

Abstract

An electro-conjugate fluid (ECF) is a dielectric liquid generating powerful flow when high DC voltage is applied with electrodes inserted. The ECF flow is generally known as a kind of electrohydrodynamics phenomenon. Although the ECF flow is applicable for attractive applications, its prediction by numerical simulation, which could be a powerful tool for optimum design, has been far from satisfactory. One of the plausible reasons for this failure is insufficient consideration of the electric double layer (EDL), in which positive and negative charges are stratified on the electrode surface. This study first confirms the presence of EDL by measuring the potential distribution between the symmetrical pole electrodes (φ0.3-mm stainless steel wires) inserted in the ECF. Subsequently, the ECF flow simulation is performed by taking into account the EDL. The governing equations of ECF flow consist of a modified Poisson-Boltzmann equation, the charge conservation with charge recombination, the Korteweg-Helmholtz equation, the continuity equation and the incompressible Navier-Stokes equation. These governing equations give the distribution of potential, electric field, charge density and flow velocity as a result of numerical computations. We demonstrate that by properly considering the EDL the numerical simulation can reasonably well reproduce the ECF flow in terms of the velocity distribution and the induced flow rate.

Keywords

• functional fluid
• electro-conjugate fluid
• electrohydrodynamics
• numerical simulation
• electric double layer