States of motion in an AC liquid film motor: experiments and theory

TL;DR

This paper combines experiments and theory to study the motion of an AC liquid film motor, revealing elastic deformation effects and revising existing models to better understand vibration behavior for applications like mixing.

Contribution

It introduces a revised theoretical model using elastic Bingham fluid dynamics and explores vibration phases in AC liquid film motors for improved technological applications.

Findings

No threshold for oscillation in AC liquid film motors.

Existence of elastic deformation before yield stress.

Distinction between elastic and plastic vibrations.

Abstract

The liquid film motor (LFM) is a simple device which serves as a laboratory to conduct experimental research in basic theoretical studies of electrohydrodynamics (EHD). In addition the LFM can play an important role in technological applications such as micro mixers and washers. In this paper we initially performed experiments to examine the theory regarding rotation and vibration of an AC LFM. While many theoretical predictions are in agreement with our experimental data, but in the threshold of vibration there is an obvious disagreement; we showed that no threshold exists and oscillation is observed in any field value. Experimental evidence showed the existence of an elastic deformation in water before reaching the yield stress and lead us to the use of the elastic Bingham fluid model. We revised the theories using this model and investigated the behaviour of a vibrating LFM which has more applications in mixing. We applied a numerical solution to derive different phases of vibration and distinguish between elastic and plastic vibrations, the latter which could be used for mixing.