Non-stationary screw flow in a toroidal channel: way to a laboratory dynamo experiment

A possibility to implement a new type of dynamo experiment, namely, a nonstation-ary dynamo in a braked toroidal channel is considered. We suggest that a helical flow with the magnetic Reynolds number sucient for screw dynamo action can develop in a toroidal channel with liquid sodium (about 100 kg) accelerated up to the frequency of 50 RPS and braked abruptly. The growth of the resulting magnetic eld is expected to be sucient to isolate dynamo eect. In this paper we present the results of hydrodynamic experiments with water prototypes. The spatial and temporal proles of the helical flow excited in a braked channel by a diverter are investigated. Numerical simulation of the magnetic eld evolution is performed for a helical flow with a prole extracted from the experimental data and scaled to the parameters of MHD apparatus. The data from the hydrodynamic experiment and the results of MHD numerical simulations are used to optimize the MHD apparatus under development. Introduction. At the very end of the XX century the long-standing experi-mental eorts to implement the self-excitation of magnetic elds by MHD dynamo was crowned with success. The MHD dynamo experiments performed in Riga [1]