INVESTIGATION OF SECONDARY FLOWS IN MAGNETOHYDRODYNAMIC CHANNELS

In magnetohydrodynamic (MHD) channel flows, electromagnetic body force s may create significant secondary flows with resultant effects on axi al velocity and turbulence distributions, electrical conductivity, bou ndary-layer voltage drops, electrode temperatures, and wall heat trans fer. An investigation of the influence of electromagnetic interaction parameter, and channel electrical configuration on the magnitude and s tructure of MHD secondary flow is reported. Two electrode configuratio ns were utilized. The first was a simulated Hall generator configurati on in which an axial current was driven through the plasma. In this co nfiguration, a two-cell secondary flow pattern with peak transverse ve locities of approximately 13% of the freestream axial velocity was obs erved. The secondary flow was initially a sensitive function of electr omagnetic interaction level, but became insensitive at high interactio n levels. For all interaction levels, the secondary flow was concentra ted in the upper two-thirds of the channel cross section. The second c onfiguration was a simulated segmented Faraday channel in which transv erse currents were driven through the plasma. A two-cell secondary flo w structure was again observed, whereas a first-order model for an inf initely finely segmented channel would predict a six-cell structure. C urrent streamline curvature due to finite electrode segmentation may e xplain this discrepancy.