A laminar dynamo driven by a steady pressure gradient

This animation portrays a dynamo generated by the motion of liquid metal up and down two iinterwoven, infinite helical pipes of rectangular cross-section. Magnetic field is spontaneously created by the initially steady pipe flow. The field grows exponentially until it reacts back upon the flow and elaborate time-dependent interactions ensue. The top 4 panels show from left to right, in a cross-sections of one of the pipes, the cross-pipe field, the down-pipe field, the down-pipe current and the rate of working of the Lorentz force alongside a time-trace of the magnetic energy. The lower 3 panels show the cross-pipe flow, the down-pipe flow and the down-pipe vorticity alongside the kinetic energy.

For these parameters (R_m=8000, R_e=27) and geometry the nonlinear solution is a-periodic and highly energetic. In this brief excerpt the mean magnetic energy is considerably larger than the kinetic. The formation of small-scale structures is marked.