The Instability Analysis Of Electrical Jets In Electrical Field

After pushing into the electrical field with high speed from the nozzle, Polymer solution is speeding up and thinning by the external field, and two axisymmetric instabilities: "Rayleigh" instability and "conducting" instability occur. This paper discusses these two kinds of axisymmetric instability. By using Giesekus model, a non-linear, viscoelastic fluid model, governing equations of slender-body jet are deduced, which includes momentum balance equation, field balance equation, conservation equation of charges and so on. Then, dispersion equations are deduced by applying small disturbances to the variables. According to the numerical results, we discuss the impact of fluid and electrical factors on jet's stability, and try to analyze the physical mechanism of instability.Through numerical analysis, we find that increasing viscosity, conductivity, external filed as well as decreasing elasticity stabilizes jet's " Rayleigh" mode; increasing external field and conductivity destabilizes jet's conducting mode; for perfect conductors, increasing surface charge stabilizes the jet; for perfect dielectrics, increasing surface charge stabilizes the jet in long wavelengths but destabilizes the jet in short wavelengths. The "Rayleigh" mode decides on the balance between the inertia and surface tension. The jet with charges has radical repulsion which also infects the "Rayleigh" mode; the physics of conducting mode is a consequence of the interaction of the electric field with the surface charge on the jet; surface tension is an irrelevant parameter for this mode. Increasing surface charge and external field will destabilize conducting mode and stabilize "Rayleigh" mode.This paper integrates the latest hydrodynamics achievements in two fields: one is the research on the constitutive equation of the rheology of viscoelastic fluid; the other is the coupling phenomenon of fluid field and electrical field. Through reading the related literatures, the author found that there was no one introducing the constitutive equation of the viscoelastic fluid into the instability research of jet with surface charge.