EVIDENCE OF SECONDARY FLOW IN FARADAY MHD GENERATORS.

Experimental evidence is presented for the existence of secondary flows in a rectangular segmented Faraday MHD generator. This evidence consists of the results of three independent experiments which measured, respectively, electrode-wall voltage drops, electrode-wall boundary-layer temperature profiles, and the decay of temperature pulses traveling down the channel in the axial direction. In each case the observed behavior for cases with applied current but without magnetic field is correctly predicted by two-dimensional models, whereas cases with magnetic field show significant departures from the predicted behavior. These departures are seen to follow a consistent pattern which could be explained by the presence of MHD-induced secondary flows. These flows are caused by the interaction of the magnetic field with a nonuniform Hall current. An experimental program is in progress with the goal of directly measuring secondary flow velocities and associated voltage drops, with net Hall current as a parameter.