DYNAMO ACTION IN THE TAYLOR-GREEN VORTEX NEAR-THRESHOLD

Dynamo action is demonstrated numerically in the forced Taylor-Green ( TG) vortex made up of a confined swirling flow composed of a shear lay er between two counter-rotating eddies, corresponding to a standard ex perimental setup in the study of turbulence. The critical magnetic Rey nolds number above which the dynamo sets in depends crucially on the f undamental symmetries of the TG vortex. These symmetries can be broken by introducing a scale separation in the how, or by letting develop a small non-symmetric perturbation which can be either kinetic and magn etic, or only magnetic. The nature of the boundary conditions for the magnetic field (either conducting or insulating) is essential in selec ting the fastest growing mode; implications of these results to a plan ned laboratory experiment are briefly discussed. (C) 1997 American Ins titute of Physics.