Topologies of velocity-field stagnation points generated by a single pair of magnets in free-surface electromagnetic experiments.
The velocity fields generated by a static pair of magnets in free-surface electromagnetically forced flows are analyzed for different magnet attitudes, ionic currents, and brine depths. A wide range of laminar velocity fields is obtained despite the forcing simplicity. The velocity fields are classified according to their temporal mean flow topology, which strongly depends on the forcing geometry but barely on its strength, even through the bifurcation to unsteady regimes. The mean flow topology possesses a major influence on the critical Reynolds number Rec under which the steady velocity fields remain stable. The qualitative comparison of the dependence of Rec on the topology is in agreement with previous works. The unsteady configurations evidence the advection of smaller flow structures by the largest scales, commonly known as "sweeping."
Imperial College London, South Kensington Campus, London SW7 2AZ, United Kingdom.
J M García
JM
de la Cruz
Imperial College London, South Kensington Campus, London SW7 2AZ, United Kingdom.
J C
JC
Vassilicos
CEA, CEA Saclay, DEN, DANS/DM2S/STMF/LIEFT 91191 Gif-sur-Yvette, France.
L
L
Rossi