Surface waves in ferrofluids under vertical magnetic field
J.
Browaeys, J.-C. Bacri, C. Flament, S. Neveu, and R. Perzynski
We present here new experimental results about the waves at the
horizontal free surface of a magnetic fluid submitted to a normal magnetic field. The waves are generated by a small
modulation at frequency of the vertical field He. Using a shadowgraph method, we are able to measure the
wavevector k of the 2D waves for a given value of He. The dispersion relation
of the surface waves is established experimentally. On the other hand, we
propose a theoretical derivation of the dispersion equation which includes a
more complete treatment of the magnetic term than the previous works. Finally,
we conclude that a linear and inviscid analysis is suffcient to fit well the experimental data, except in the
vicinity of the critical field where a
surface instability occurs.