33 research outputs found
Stretching and squeezing of sessile dielectric drops by the optical radiation pressure
We study numerically the deformation of sessile dielectric drops immersed in
a second fluid when submitted to the optical radiation pressure of a continuous
Gaussian laser wave. Both drop stretching and drop squeezing are investigated
at steady state where capillary effects balance the optical radiation pressure.
A boundary integral method is implemented to solve the axisymmetric Stokes flow
in the two fluids. In the stretching case, we find that the drop shape goes
from prolate to near-conical for increasing optical radiation pressure whatever
the drop to beam radius ratio and the refractive index contrast between the two
fluids. The semi-angle of the cone at equilibrium decreases with the drop to
beam radius ratio and is weakly influenced by the index contrast. Above a
threshold value of the radiation pressure, these "optical cones" become
unstable and a disruption is observed. Conversely, when optically squeezed, the
drop shifts from an oblate to a concave shape leading to the formation of a
stable "optical torus". These findings extend the electrohydrodynamics approach
of drop deformation to the much less investigated "optical domain" and reveal
the openings offered by laser waves to actively manipulate droplets at the
micrometer scale
Numerical simulation of channel segregates during alloy solidification using TVD schemes.
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