Spatial effects in a railgun plasma armature

The results of mathematical simulation of thermal, mechanical and electromagnetic interaction of railgun plasma armature and channel walls are presented. A generalized 2D-approach taking into account turbulent friction, radiative and turbulent heat transfer and spatial inhomogeneity of the magnetic field was used. The heat regime of electrodes was considered in the 2D-approach. The momentum and energy transfer from the flow core to the electrodes and the process of involving the erosion mass into acceleration were investigated in detail. It has been shown that magnetic field inhomogeneity causing the appearance of spatial induction currents influences essentially the momentum, energy and mass balance in the near-electrode region and the armature characteristics as a whole. It leads to an additional drag force and the release of Joule heat near the rail surface and to the increase in erosion. Under some conditions this can cause instability of plasma armature and its sharp extension. Calculations have shown that the electrode melting, destruction of the liquid film, involving of drops into acceleration and their vaporization in the flow seem to be the most probable mechanism of plasma mass increase for typical regimes of railgun operation.