6,999 research outputs found
Dispersions of ellipsoidal particles in a nematic liquid crystal
Colloidal particles dispersed in a partially ordered medium, such as a liquid
crystal (LC) phase, disturb its alignment and are subject to elastic forces.
These forces are long-ranged, anisotropic and tunable through temperature or
external fields, making them a valuable asset to control colloidal assembly.
The latter is very sensitive to the particle geometry since it alters the
interactions between the colloids. We here present a detailed numerical
analysis of the energetics of elongated objects, namely prolate ellipsoids,
immersed in a nematic host. The results, complemented with qualitative
experiments, reveal novel LC configurations with peculiar topological
properties around the ellipsoids, depending on their aspect ratio and the
boundary conditions imposed on the nematic order parameter. The latter also
determine the preferred orientation of ellipsoids in the nematic field, because
of elastic torques, as well as the morphology of particles aggregates.Comment: 31 pages, 11 figure
Finite Element Simulation of Dense Wire Packings
A finite element program is presented to simulate the process of packing and
coiling elastic wires in two- and three-dimensional confining cavities. The
wire is represented by third order beam elements and embedded into a
corotational formulation to capture the geometric nonlinearity resulting from
large rotations and deformations. The hyperbolic equations of motion are
integrated in time using two different integration methods from the Newmark
family: an implicit iterative Newton-Raphson line search solver, and an
explicit predictor-corrector scheme, both with adaptive time stepping. These
two approaches reveal fundamentally different suitability for the problem of
strongly self-interacting bodies found in densely packed cavities. Generalizing
the spherical confinement symmetry investigated in recent studies, the packing
of a wire in hard ellipsoidal cavities is simulated in the frictionless elastic
limit. Evidence is given that packings in oblate spheroids and scalene
ellipsoids are energetically preferred to spheres.Comment: 17 pages, 7 figures, 1 tabl
Nonlinear waves in heterogeneous elastic rods via homogenization
We consider the propagation of a planar loop on a heterogeneous elastic rod with a periodic microstructure consisting of two alternating homogeneous regions with different material properties. The analysis is carried out using a second-order homogenization theory based on a multiple scale asymptotic expansion
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