Dependence of frequency and phase velocity of plasma jet hydrodynamic instability on sound velocity

Abstract

In this work detailed study of dependence of oscillation parameters of Rayleigh instability on the plasma flow property was performed by analysis of oscillations of light emitted by plasma jet. Plasma flow was generated by a water stabilized or hybrid steamargon plasma torch with an external anode. The frequency and the phase velocity of flow oscillations as well as the velocity of plasma flow and sound velocity were determined for various argon flow rates and various arc currents. The velocity of plasma flow and sound velocity were determined from the streamwise and the counter-streamwise velocity of shock waves propagation, initiated by anode breakdowns in a restrike mode of the anode attachment. It was found that the frequency and the phase velocity of studied coherent oscillations linearly depend on the sound velocity and the phase velocity is about tenth of sound velocity. This dependence is only weakly influenced directly by plasma velocity and mass flow rate.