Magnetic Field Gradient Effects on Magnetic Fluid Stabilization

The penetrating finger instability which develops when a less viscous fluid pushes a more yiscous fluid can be stabilized through the use of a magnetizable fluid in the presence of a magnetic field tangential to the interface. A uniform magnetic field only stabilizes suitably short waves traveling along the field lines. Transverse waves of all wavelengths and orientations are also stabilized if the tangential magnetic field is non-uniform with field decreasing in the direction away from the magnetically permeable fluid. Confirming experiments are described using laboratory sandpacks.