Morphology of Taylor Cone in Stable Regime: Experimental and Numerical Insights

In the stable cone-jet regime, liquid usually presents the shape of a cone extended by a jet at its apex, with jet breakup yielding fine drops. The dynamics of the Taylor cone critically affect the stability of the jet and further determine the jet and/or drop size. In the present work, the morphology of the Taylor cone, cone length, and cone angle were studied through experimental and numerical means, where the operating parameters and liquid properties are considered. An increase in electric potential can elevate surface charge density, leading to an inward contraction of the cone, which results in the Taylor cone going from convex to straight to concave, accompanied by the cone length decreasing and the cone angle increasing. Large flow rate can enhance inertial force and kinetic energy, leading to liquid accumulation on the cone, and the cone transforms from straight to convex, the cone length increases, and the cone angle decreases. Furthermore, low surface tension cannot sufficiently counteract the normal electric stress, promoting concave cone formation, while high surface tension forms a convex cone with minimization of surface energy. High conductivity can reduce charge relaxation time, driving charge to escape along the jet direction, inducing a transition from concave to straight to convex cones with a concurrent increase in conduction current. The viscosity keeps the shape of the straight cone. High viscosity lengthens the cone and enlarges the jet radius by slowing down the axial flow while suppressing the convection current by inhibiting the electric charge advection.