Experimental investigation of surface instability of a thin layer of a magnetic fluid

TL;DR

This study experimentally explores how a thin layer of magnetic fluid develops surface patterns under a magnetic field, revealing conditions for instability and pattern formation, and comparing results with existing theories.

Contribution

It provides new experimental data on surface instability patterns of magnetic fluids at microscale and compares these findings with theoretical predictions.

Findings

Formation of parallel ridges and hexagonal peaks observed.

Instability wave number depends on physical parameters.

Development time of instability measured and analyzed.

Abstract

In the present work the instability of a flat horizontal thin layer of a magnetic fluid (the depth of no more than 50 \mum) under the action of a uniform magnetic field is studied experimentally. It was revealed that the development of instability under the action of tilted magnetic field can lead to the formation of parallel ridges on a fluid surface; the ridges undergo a transformation into hexagonal system of conical peaks with the magnetic field increasing. The necessary conditions for the formation of these surface patterns are studied. It was found that the development of instability of quite thin layers may result in layers breakup. The dependencies of instability wave number on the system physical parameters are obtained. The time for the development of instability is measured. The experimental results are compared with the existing theory and discussed.