Three-dimensional structures of MHD flow in a disk generator

Abstract

Three-dimensional nonuniform plasmas and boundary layers have been studied numerically under an MHD interaction. The nonuniform plasma of "streamer" owing to weak ionization of seed material has a spiral structure in the r-/spl theta/ plane, and the plasma becomes almost uniform between the walls in the r-z plane. This structure is almost the same as that in our previous paper (1997), where the gas (heavy particle) properties are assumed to be invariant and steady. In addition to the streamer, the nonuniform plasma of "domain" owing to weak ionization of noble gas is revealed. The domain has the structure perpendicular to the streamer. In a strong MHD interaction case, the static pressure considerably increases in the upstream region of a generation channel, and the pseudo-shock waves appear in the generator, but the plasma is almost uniform along the /spl theta/ direction. The boundary layer in the strong MHD interaction is considerably thick, and in the broad region near the wall the Hall current flows reversely. In the weak MHD interaction case, the plasma forms a nonuniform structure along the /spl theta/ direction, and the Hall current does not always flow in the opposite direction even on the insulator wall since the azimuthal electric field is not zero.