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Elborai, S.M., D.K. Kim, X. He, S.-H. Lee, S. Rhodes, and M. Zahn, “Self-Forming, Quasi-Two-Dimensional Magnetic Fluid Patterns With Applied In-Plane-Rotating and DC-Axial Magnetic Fields,” Journal of Applied Physics, Vol. 97, 10Q303.1-3, 2005. Abstract We report flow instabilities with simultaneous, in-plane-rotating and dc-axial uniform magnetic fields. In uniform dc-axial magnetic fields, a ferrofluid drop in a Hele-Shaw cell with an ∼ 1.0-mm gap forms the familiar labyrinth pattern. With subsequent application of an ∼ 100-G rms in-plane, 20–40-Hz rotating uniform magnetic field, smooth spirals form. If the rotating magnetic field is applied first, the drop holds together for low dc-axial magnetic fields and no labyrinth pattern develops. If the dc magnetic field is subsequently increased above a threshold value, the ferrofluid drop abruptly transforms into many ferrofluid droplets arranged in a regular pattern.
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