Linear stability of confined coaxial jets in the presence of gas velocity oscillations with heat and mass transfer

In this work, the linear temporal stability of a confined coaxial jet has been examined in the presence of gas velocity oscillations with heat and mass transfer. The viscous potential flow theory was applied to account for the liquid and gas viscosities. Results suggest that gas velocity oscillations have a destabilizing effect. The forcing frequency restrained the instability in the parametric unstable region but enhanced the instability in the Kelvin-Helmholtz (K-H) unstable region. Heat and mass transfer decreased the curvature of the surface wave directly and enhanced the hydrodynamic force via the phase change. Heat and mass transfer had a stabilizing effect on the capillary instability, and a dual effect on K-H instability without oscillations. Results similar to the K-H instability were discovered when the oscillations were considered. Gas viscosity played a destabilizing role with the effect of heat and mass transfer, especially reducing the critical velocity for the appearance of the instability; moreover, the liquid viscosity had a stabilizing effect for all the cases discussed.