52 research outputs found
Saddle-Node Bifurcation to Jammed State for Quasi-One-Dimensional Counter Chemotactic Flow
The transition of a counter chemotactic particle flow from a free-flow state
to a jammed state in a quasi-one-dimensional path is investigated. One of the
characteristic features of such a flow is that the constituent particles
spontaneously form a cluster that blocks the path, called a path-blocking
cluster (PBC), and causes a jammed state when the particle density is greater
than a threshold value. Near the threshold value, the PBC occasionally desolve
itself to recover the free flow. In other words, the time evolution of the size
of the PBC governs the flux of a counter chemotactic flow. In this paper, on
the basis of numerical results of a stochastic cellular automata (SCA) model,
we introduce a Langevin equation model for the size evolution of the PBC that
reproduces the qualitative characteristics of the SCA model. The results
suggest that the emergence of the jammed state in a quasi-one-dimensional
counter flow is caused by a saddle-node bifurcation.Comment: 5pages, 8figure
Segregation pattern reorientation of granular mixture on horizontally oscillating tray
Reorientation of the segregation pattern of a binary granular mixture on a
two-dimensional hor- izontally oscillating tray is numerically realized. The
mixture consists of large-and-heavy particles and small-and-light particles,
the segregation pattern of which shows a transition between a striped pattern
perpendicular to the oscillation and that parallel to the oscillating direction
according to the change of area-fractions of two types of particles. The
transition mechanism is discussed on the basis of a simplified 1-dimensional
dynamics.Comment: 10 pages, 6 figure
Stability of transverse dunes against perturbations; a theoretical study using dune skeleton model
The dune skeleton model is a reduced model to describe the formation process
and dynamics of characteristic types of dunes emerging under unidirectional
steady wind. Using this model, we study the dependency of the morphodynamics of
transverse dunes on the initial random perturbations and the lateral field
size. It was found that i) an increase of the lateral field size destabilizes
the transverse dune to cause deformation of a barchan, ii) the initial random
perturbations decay with time by the power function until a certain time;
thereafter, the dune shapes change into three phases according to the amount of
sand and sand diffusion coefficient, iii) the duration time, until the
transverse dune is broken, increases exponentially with increasing the amount
of sand and sand diffusion coefficient. Moreover, under the condition without
the sand supply from windward ground, the destabilization of transverse dune in
this model qualitatively corresponds to the subaqueous dunes in water tank
experiments.Comment: 7pages, 8figure
Swarming of Self-Propelled Camphor Boats
When an ensemble of self-propelled camphor boats move in a one-dimensional
channel, they exhibit a variety of collective behaviors. Under certain
conditions, the boats tend to cluster together and move in a relatively tight
formation. This type of behavior, referred to as clustering or swarming here,
is one of three types recently observed in experiment. Similar clustering
behavior is also reproduced in simulations based on a simple theoretical model.
Here we examine this model to determine the clustering mechanism and the
conditions under which clustering occurs. We also propose a method of
quantifying the behavior that may be used in future experimental work.Comment: 4 pages, 5 figure
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