Deformation of a Neutrally Buoyant Drop of Magnetic Fluid Excited Non-intrusively by an External Magnetic Field

Abstract. An experimental study was performed on deformation of a neutrally buoyant drop of a magnetic fluid exposed to a magnetic field. Neutral buoyancy of the drop was realized by placing it in an aqueous solution of lithium bromide whose density was adjusted to the former, and the magnetic field was applied to observe shape change in the absence of contacting solid boundary. When a steady magnetic field was applied, the drop was deformed into an ellipsoid of revolution, whose aspect ratio was determined by the balance of the surface tension and the Maxwell’s stress. When the magnetic field was oscillating, eigen modes of oscillation were induced under certain conditions. In other circumstances, shape of the drop changed with frequency two times of the externally applied one. The present method is applicable to estimate surface tension coefficient and magnetic susceptibility of the magnetic fluid. 1