1,651 research outputs found
One-Dimensional Approximation of Viscous Flows
Attention has been paid to the similarity and duality between the
Gregory-Laflamme instability of black strings and the Rayleigh-Plateau
instability of extended fluids. In this paper, we derive a set of simple
(1+1)-dimensional equations from the Navier-Stokes equations describing thin
flows of (non-relativistic and incompressible) viscous fluids. This
formulation, a generalization of the theory of drop formation by Eggers and his
collaborators, would make it possible to examine the final fate of
Rayleigh-Plateau instability, its dimensional dependence, and possible
self-similar behaviors before and after the drop formation, in the context of
fluid/gravity correspondence.Comment: 17 pages, 3 figures; v2: refs & comments adde
Simulation of a Dripping Faucet
We present a simulation of a dripping faucet system. A new algorithm based on
Lagrangian description is introduced. The shape of drop falling from a faucet
obtained by the present algorithm agrees quite well with experimental
observations. Long-term behavior of the simulation can reproduce period-one,
period-two, intermittent and chaotic oscillations widely observed in
experiments. Possible routes to chaos are discussed.Comment: 20 pages, 15 figures, J. Phys. Soc. Jpn. (in press
Identification of structure in condensed matter with the topological cluster classification
We describe the topological cluster classification (TCC) algorithm. The TCC
detects local structures with bond topologies similar to isolated clusters
which minimise the potential energy for a number of monatomic and binary simple
liquids with particles. We detail a modified Voronoi bond detection
method that optimizes the cluster detection. The method to identify each
cluster is outlined, and a test example of Lennard-Jones liquid and crystal
phases is considered and critically examined.Comment: 28 pages, 28 figure
Hydrodynamic theory of de-wetting
A prototypical problem in the study of wetting phenomena is that of a solid
plunging into or being withdrawn from a liquid bath. In the latter, de-wetting
case, a critical speed exists above which a stationary contact line is no
longer sustainable and a liquid film is being deposited on the solid.
Demonstrating this behavior to be a hydrodynamic instability close to the
contact line, we provide the first theoretical explanation of a classical
prediction due to Derjaguin and Levi: instability occurs when the outer, static
meniscus approaches the shape corresponding to a perfectly wetting fluid
Air entrainment through free-surface cusps
In many industrial processes, such as pouring a liquid or coating a rotating
cylinder, air bubbles are entrapped inside the liquid. We propose a novel
mechanism for this phenomenon, based on the instability of cusp singularities
that generically form on free surfaces. The air being drawn into the narrow
space inside the cusp destroys its stationary shape when the walls of the cusp
come too close. Instead, a sheet emanates from the cusp's tip, through which
air is entrained. Our analytical theory of this instability is confirmed by
experimental observation and quantitative comparison with numerical simulations
of the flow equations
Universal behavior of multiplicity differences in quark-hadron phase transition
The scaling behavior of factorial moments of the differences in
multiplicities between well separated bins in heavy-ion collisions is proposed
as a probe of quark-hadron phase transition. The method takes into account some
of the physical features of nuclear collisions that cause some difficulty in
the application of the usual method. It is shown in the Ginzburg-Landau theory
that a numerical value of the scaling exponent can be determined
independent of the parameters in the problem. The universality of
characterizes quark-hadron phase transition, and can be tested directly by
appropriately analyzed data.Comment: 15 pages, including 4 figures (in epsf file), Latex, submitted to
Phys. Rev.
Bifurcation Diagram for Compartmentalized Granular Gases
The bifurcation diagram for a vibro-fluidized granular gas in N connected
compartments is constructed and discussed. At vigorous driving, the uniform
distribution (in which the gas is equi-partitioned over the compartments) is
stable. But when the driving intensity is decreased this uniform distribution
becomes unstable and gives way to a clustered state. For the simplest case,
N=2, this transition takes place via a pitchfork bifurcation but for all N>2
the transition involves saddle-node bifurcations. The associated hysteresis
becomes more and more pronounced for growing N. In the bifurcation diagram,
apart from the uniform and the one-peaked distributions, also a number of
multi-peaked solutions occur. These are transient states. Their physical
relevance is discussed in the context of a stability analysis.Comment: Phys. Rev. E, in press. Figure quality has been reduced in order to
decrease file-siz
Changing shapes in the nanoworld
What are the mechanisms leading to the shape relaxation of three dimensional
crystallites ? Kinetic Monte Carlo simulations of fcc clusters show that the
usual theories of equilibration, via atomic surface diffusion driven by
curvature, are verified only at high temperatures. Below the roughening
temperature, the relaxation is much slower, kinetics being governed by the
nucleation of a critical germ on a facet. We show that the energy barrier for
this step linearly increases with the size of the crystallite, leading to an
exponential dependence of the relaxation time.Comment: 4 pages, 5 figures. Accepted by Phys Rev Let
Wavelength Scaling and Square/Stripe and Grain Mobility Transitions in Vertically Oscillated Granular Layers
Laboratory experiments are conducted to examine granular wave patterns near
onset as a function of the container oscillation frequency f and amplitude A,
layer depth H, and grain diameter D. The primary transition from a flat grain
layer to standing waves occurs when the layer remains dilated after making
contact with the container. With a flat layer and increasing dimensionless peak
container acceleration G = 4 pi^2 f^2 A/g (g is the acceleration due to
gravity), the wave transition occurs for G=2.6, but with decreasing G the waves
persist to G=2.2. For 2.2<G<3.8, patterns are squares for f<f_ss and stripes
for f>f_ss; H determines the square/stripe transition frequency
f_ss=0.33(g/H)^0.5. The dispersion relations for layers with varying H collapse
onto the curve L/H=1.0+1.1[f(H/g)^0.5]^(-1.32 +/- 0.03) (L is the wavelength)
when the peak container velocity v exceeds a critical value v_gm of
approximately 3 (Dg)^0.5. Local collision pressure measurements suggest that
v_gm is associated with a transition in the horizontal grain mobility: for
v>v_gm, there is a hydrodynamic-like horizontal sloshing motion, while for
v<v_gm, the grains are essentially immobile and the stripe pattern apparently
arises from a bending of the granular layer. For f at v_gm less than f_ss and
v<v_gm, patterns are tenuous and disordered.Comment: 21 pages, 15 figures, submitted to Physica
Asymptotic theory for a moving droplet driven by a wettability gradient
An asymptotic theory is developed for a moving drop driven by a wettability
gradient. We distinguish the mesoscale where an exact solution is known for the
properly simplified problem. This solution is matched at both -- the advancing
and the receding side -- to respective solutions of the problem on the
microscale. On the microscale the velocity of movement is used as the small
parameter of an asymptotic expansion. Matching gives the droplet shape,
velocity of movement as a function of the imposed wettability gradient and
droplet volume.Comment: 8 fig
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