Parametric instability of conducting, slightly viscous liquid jets under periodic electric fields

A temporal, linear, modal stability analysis is presented for conducting liquid jets in air subjected to time periodic electric fields. The field is originated by a mixed ac-dc potential difference between the jet and a long coaxial cylindrical electrode. As a result of the Lagrange function formalism a governing equation for the time dependent amplitude of deformation is obtained. Slightly viscous liquids may be also described by the model. The stability is obtained by inspection of the Floquet exponents of the solutions. We extend previous results for de voltages with a discussion on the observability of parametric resonances arising in the small wavelength region of the spectrum, a region that would be stable under de fields.