Title : Stability of ferrofluid cylinder in an azimuthal magnetic field : theory and experiment.
Contact : Nathanael Machicoane
Abstract : We study the stability of a ferrofluid cylinder placed in a non-magnetic fluid and immersed in an azimuthal magnetic field. The field is created by a rectilinear wire traversed by a current and located at the cylinder center. After formulating the problem of ferrohydrodynamics, we conduct linear stability analysis. The developed model is then compared with experimental data taken from the literature for the unstable and stable cases delimited by a magnetic Bond number equalling unity. A good agreement with the data is found concerning the values of the wavelength and the growth rate of the instability. However, in the experiment, the growth rate is observed to be higher for the thinner layers of ferrofluid, in disagreement with the theoretical predictions. In order to solve this issue and further explore the comparison, we have conducted a new campaign of experiments. The aim of the work on ferrofluid cylinders is to identify new possibilities of controlling drops formed by liquid jet breakup for applications in the printing domain and medical field.