  An electrohydrodynamic numerical model is used to explore the electrospray
emission behavior of both moderate and high electrical conductivity liquids
under electrospray conditions. The Volume-of-Fluid method, incorporating a
leaky-dielectric model with a charge relaxation consideration, is used to
conserve charge to accurately model cone-jet formation and droplet breakup. The
model is validated against experiments and agrees well with both droplet
diameters and charge-to-mass ratio of emitted progeny droplets. The model
examines operating conditions such as flow rate and voltage, with fluid
properties also considered, such as surface tension, electrical conductivity,
and viscosity for both moderate and high conductivity. For high conductivity
and surface tension, the results show that high charge concentration along with
the meniscus and convex cone shape results in a higher charge-to-mass ratio of
the emitted droplets while lower conductivity and surface tension tend towards
concave cone shapes and lower charge-to-mass droplets. Recirculation flows
inside the bulk liquid are investigated across a range of non-dimensional flow
rates, and electric Reynolds numbers. For high conductivity liquid emission at
the minimum stable flow rate, additional recirculation cells develop near the
cone tip suggesting the onset of the axisymmetric instability.
