Dynamic equilibrium of streamer filaments in a homogeneous flow field

From the experiments performed in the Eindhoven MHD facilities it is clear that the currents in a noble gas-alkali MHD generator are constricted in narrow channels, called streamers. These streamers appear to exist as a bunch of several hundred tubes with high electrical conduction, called filaments, whereas the surrounding gas has a low electrical conductivity. The aim of the paper is to find an explanation how these fine filaments can be sustained in the supersonic flow, moving downstream with slightly lower velocity than the main flow. At the Institute for High Temperatures (IVTAN) a model has been developed where these streamers filaments are considered as liquid tubes in a surrounding liquid. The electromagnetic forces are prescribed and applied only inside the tubes. The experimental fact that the bunch of filaments moves through the MHD channel with velocities slightly different from the surrounding nonconducting gas led to a model where the mutual influence of neighboring filaments was taken into account by dividing the space into three regions: an undisturbed outer flow, a cylinder around the filaments with radium equal to half the distance between the filaments, and the filament tube itself. The calculations performed show that inside the tubes two counter-rotating vortices are produced with velocities close to the relative velocity between filament and surrounding gas. The strong mixing of the gas inside the filament validates the assumption of constant physical parameters within the filament. Further it is shown that the viscous forces can balance the strong electromagnetic ones. As no methods are known to exist to increase the size and current carrying capacity of the filaments the experiments on linear Ar-Cs MHD generators are abandoned