On spatial instability of electrically forced axisymmetric jets with variable applied field

This paper considers the problem of instability of electrically forced axisymmetric jets with respect to spatially growing disturbances and in the presence of a variable applied electric field. A mathematical model, which is developed for the dependent variables of such disturbances, is based on the relevant approximated versions of the equations of the electrohydrodynamics for an electrically forced jet flow. The approximations include the assumptions that the length scale along the axial direction of the jet is much larger than that in the radial direction of the jet and the disturbances are axisymmetric and infinitesimal in amplitude. For neutral temporal stability boundary, we find, in particular, two new spatial modes of instabilities under certain conditions. Both modes are found to be enhanced with increasing the strength of the field. The more dominant instability mode is found to exist for a wider range of values of the wave number in the axial direction. The effect of variable applied electric field is found to increase the growth rates of the disturbances but operate over a more restricted domain in the axial wave number.