5 research outputs found
Pattern Selection in a Phase Field Model for Directional Solidification
A symmetric phase field model is used to study wavelength selection in two
dimensions. We study the problem in a finite system using a two-pronged
approach. First we construct an action and, minimizing this, we obtain the most
probable configuration of the system, which we identify with the selected
stationary state. The minimization is constrained by the stationary solutions
of stochastic evolution equations and is done numerically. Secondly, additional
support for this selected state is obtained from straightforward simulations of
the dynamics from a variety of initial states.Comment: 7 pages, 6 figures, to appear in Physica
Interruption of torus doubling bifurcation and genesis of strange nonchaotic attractors in a quasiperiodically forced map : Mechanisms and their characterizations
A simple quasiperiodically forced one-dimensional cubic map is shown to
exhibit very many types of routes to chaos via strange nonchaotic attractors
(SNAs) with reference to a two-parameter space. The routes include
transitions to chaos via SNAs from both one frequency torus and period doubled
torus. In the former case, we identify the fractalization and type I
intermittency routes. In the latter case, we point out that atleast four
distinct routes through which the truncation of torus doubling bifurcation and
the birth of SNAs take place in this model. In particular, the formation of
SNAs through Heagy-Hammel, fractalization and type--III intermittent mechanisms
are described. In addition, it has been found that in this system there are
some regions in the parameter space where a novel dynamics involving a sudden
expansion of the attractor which tames the growth of period-doubling
bifurcation takes place, giving birth to SNA. The SNAs created through
different mechanisms are characterized by the behaviour of the Lyapunov
exponents and their variance, by the estimation of phase sensitivity exponent
as well as through the distribution of finite-time Lyapunov exponents.Comment: 27 pages, RevTeX 4, 16 EPS figures. Phys. Rev. E (2001) to appea
Singularite anguleuse d'une ligne de contact en movement sur un substrat solide (Corner singularity of a contact line moving on a solid substrate)
In conditions of partial wetting and at sufficiently high capillary number Ca, a dynamic contact line that recedes on a solid surface assumes a 'saw-tooth' shape. We show that the flow inside this liquid 'corner' is a similarity solution of the lubrication equations governing steady thin-film flows in which the free surface is cone shaped. The interface slope Φ#169; defined in its symmetry plane is linked to the corner angle 2φ by the approximate relationship Φ#169;3≈(3/2) Catan2φ. We also suggest a possible explanation of droplet emission from the corner which occurs when φ reaches π/6