MAGNETOHYDRODYNAMIC INSTABILITY OF AN ANNULAR GAS-JET OF DOUBLE PERTURBED INTERFACES

The magnetohydrodynamic (MHD) instability of an annular gas jet of dou ble perturbed interfaces is analyzed. The MHD basic equations are line arized and solved. A general stability criterion is derived and discus sed analytically and the results are confirmed numerically. Several st ability criteria are recovered from the present relation. The capillar y force is, acting along the gas-liquid interface, destabilizing only for small axisymmetric wavelengths and stable for all the rest. The el ectromagnetic forces in the gas and liquid regions are strongly stabil izing for all wavelengths in all modes of disturbance, and this is int erpreted physically. Above a certain value of the applicable magnetic field, the electromagnetic force influences suppress the capillary ins tability and stability sets in. The thicker the radius of the liquid c ylinder relative to that of the gas cylinder, the greater the destabil izing influence and the larger the MHD unstable domains for the same v alue of the fundamental basic magnetic field. Physically, the suppress ion of the capillary instability is due to the fact that the Lorentz f orce leads to twisting and bending of the lines of force and, moreover , it gives a measure of rigidity to the conducting fluid. Copyright (C ) 1996 Elsevier Science Ltd