Stability of fluid films of nanoscale thickness involving contact lines

Tuesday, March 27, 2018 - 1:30pm - 2:00pm
Lind 305
Lou Kondic (New Jersey Institute of Technology)
We discuss instabilities of fluid films of nanoscale thickness,
with a particular focus on films where the destabilizing mechanism
allows for linear instability, metastability, and absolute stability,
depending on the mean film thickness. Our study is motivated by nematic
liquid crystal films; however similar instability mechanisms, and forms
of the effective disjoining pressure, appear in other contexts, such as
the well- studied problem of polymeric films on two-layered substrates.
The analysis is carried out within the framework of the long-wave
approximation, which leads to a fourth order nonlinear partial different
equation for the film thickness. Within the considered formulation,
the nematic character of the film leads to an additional contribution to
the disjoining pressure, changing its functional form. This effective
disjoining pressure is characterized by the presence of a local maximum
for non-vanishing film thickness. Such a form leads to complicated instability
evolution that we study by analytical means, including the application of
marginal stability criteria, and by extensive numerical simulations that
help us develop a better understanding of instability evolution in the
nonlinear regime. These simulations, carried out on GPUs, allow for
considering large domains so that instability development is not influenced
by the domain boundaries. This combination of analytical and computational
techniques allows us to reach novel understanding of relevant instability
mechanisms, and of their influence on transient and fully developed fluid
film morphologies.