Coupled fluid-flow and magnetic-field simulation of the Riga dynamo experiment

Magnetic fields of planets, stars, and galaxies result from self-excitation in moving electro-conducting fluids, also known as dynamo effect. This phenomenon was recently experimentally confirmed in the Riga dynamo experiment, consisting of a helical motion of sodium in a long pipe followed by a straight back-flow in a surrounding annular passage, which provided adequate conditions for magnetic field self-excitation. We report here on the first attempt to simulate computationally the Riga experiment. The velocity and turbulence fields are modelled by a finite-volume Navier-Stokes solver using a Reynolds-Averaged-Navier-Stokes (RANS) turbulence model. The magnetic field is computed by an Adams-Bashforth finite-difference solver. The coupling of the two computational codes, although performed sequentially, provides an improved understanding of the interaction between the fluid velocity and magnetic fields in the saturation regime of the Riga dynamo experiment under realistic working conditions.