Breakup of a Fluid Thread in a Confined Geometry: Droplet-Plug Transition Perturbation Sensitivity and Kinetic Stabilization With Confinement .
Breakup of a Fluid Thread in a Confined Geometry:
Droplet-Plug Transition Perturbation Sensitivity and
Kinetic Stabilization With Confinement .
(1356 K)
Hagedorn, J. G.; Martys, N. S.; Douglas, J. F.
056312;
Physical Review E, Vol. 69, No. 4, 056312/1-18, May
2004.
Keywords:
Lattice Bolzmann; capillary breakup; Taylor-Tomotka;
stability; surface tensions
Abstract:
We investigate the influence of geometrical confinement
on the breakup of long fluid threads in the absence of
imposed flow using a lattice Boltzmann model. Our
simulations primarily focus on the case of threads
centered coaxially in a tube filled with another
Newtonian fluid and subjected to both impulsive and
random perturbations. We observe a significant slowing
down of the rate of thread breakup "kinetic
stabilization" over a wide range of the confinement, and
find that the relative surface energies of the liquid
components influence this effect. There is a transition
in the late-stage morphology between spherical droplets
and tube "plugs." Unstable distorted droplets
"capsules") form as transient structures for
intermediate confinement. Surprisingly, the thread
breakup process for more confined threads is found to be
sensitive to the nature of the intial thread
perturbation. Localized impulsive perturbations "taps"
cause a "bulging" of the fluid at the wall, followed by
thread breakup through the propagation of a wavelike
disturbance "end-pinch instability" initiating from the
thread rupture point. Random impulses along the thread,
modeling thermal fluctuations, lead to a complex breakup
process involving a competition between the Raleigh and
end-pinch instabilities. We also briefly compare our
tube simulations to threads confined between parallel
plates and to multiple interacting threads under
confinement.
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National Institute of Standards and Technology
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