Author:
HA JONG-WOOK,YANG SEUNG-MAN
Abstract
In this article, we considered experimentally the deformation and breakup of
Newtonian and non-Newtonian conducting drops in surrounding fluid subjected to a
uniform electric field. First, we examined three distinctive cases of Newtonian-fluid
pairs with different relative conductivities, namely highly conducting drops, conducting
drops and slightly conducting drops. The results on the Newtonian fluids
demonstrated that when the conductivity of the drop is very large relative to that
of the surrounding fluid, the deformation response of such highly conducting drops
is described well by the electrohydrostatic theory, especially with regard to the prediction
of the critical point. Specifically, when the ratio of drop to continuous-phase resistivity,
R, was less than 10−5, the electrohydrostatic theory was quite
satisfactory. Then, the non-Newtonian effect on the drop deformation and breakup was studied for highly
conducting drops which satisfied the condition R < O(10−5).
The highly conducting drop became stable in a weak or moderate field strength when either the
drop or the continuous phase was non-Newtonian. On the other hand, when both the
phases were non-Newtonian, more complicated responses were observed depending
on the ratio of zero-shear-rate viscosities. Although the effects of the rheological
properties are minimal on all features away from the critical conditions for breakup
or prior to the instability, the non-Newtonian properties have a significant influence
during drop burst, which is accompanied by large velocities and velocity gradients.
In particular, when the ratio of the zero-shear-rate viscosity of the drop to that of
the ambient fluid was much larger than unity, non-Newtonian properties of the drop
phase enhanced the drop stability. Conversely, the elasticity of the continuous phase
deteriorated the drop stability. Meanwhile if the zero-shear-rate viscosity ratio was
much smaller than unity, the elasticity of the continuous phase produced a stabilizing
effect. The effects of resistivity and viscosity ratios on the breakup modes were also
investigated. When at least one of the two contiguous phases possessed considerable
non-Newtonian properties, tip streaming appeared.
Publisher
Cambridge University Press (CUP)
Subject
Mechanical Engineering,Mechanics of Materials,Condensed Matter Physics
Cited by
166 articles.
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