Instability of magnetic fluid in a narrow gap between plates

The behaviour of a layer of magnetic fluid in a plane capillary subjected to a uniform magnetic field is studied numerically. Two different types of instabilities arise as the intensity of the magnetic field increases. For small contact angles the layer breaks along the capillary axis and spreads over the capillary wall whereas for large contact angles the layer elongates in the central part up to its separation from the walls. Critical parameters and shapes are studied by solving the coupled nonlinear system of differential equations numerically.