2,503 research outputs found
Order-disorder transitions in a sheared many body system
Motivated by experiments on sheared suspensions that show a transition
between ordered and disordered phases, we here study the long-time behavior of
a sheared and overdamped 2-d system of particles interacting by repulsive
forces. As a function of interaction strength and shear rate we find
transitions between phases with vanishing and large single-particle diffusion.
In the phases with vanishing single-particle diffusion, the system evolves
towards regular lattices, usually on very slow time scales. Different lattices
can be approached, depending on interaction strength and forcing amplitude. The
disordered state appears in parameter regions where the regular lattices are
unstable. Correlation functions between the particles reveal the formation of
shear bands. In contrast to single particle densities, the spatially resolved
two-particle correlation functions vary with time and allow to determine the
phase within a period. As in the case of the suspensions, motion in the state
with low diffusivity is essentially reversible, whereas in the state with
strong diffusion it is not.Comment: 12 pages, 13 figures; Supplemental Movies:
https://youtu.be/oFcrWo9Vs6E, https://youtu.be/tcowb7o05JQ,
https://youtu.be/GkEUwycn7V4, https://youtu.be/k-XCo8CWFU
On statistically stationary homogeneous shear turbulence
A statistically stationary turbulence with a mean shear gradient is realized
in a flow driven by suitable body forces. The flow domain is periodic in
downstream and spanwise directions and bounded by stress free surfaces in the
normal direction. Except for small layers near the surfaces the flow is
homogeneous. The fluctuations in turbulent energy are less violent than in the
simulations using remeshing, but the anisotropy on small scales as measured by
the skewness of derivatives is similar and decays weakly with increasing
Reynolds number.Comment: 4 pages, 5 figures (Figs. 3 and 4 as external JPG-Files
High-temperature liquid-mercury cathodes for ion thrusters Quarterly progress report, 1 Dec. 1966 - 28 Feb. 1967
High temperature liquid mercury cathodes for ion thrusters - thermal design analysi
Anomalous power law of quantum reversibility for classically regular dynamics
The Loschmidt Echo M(t) (defined as the squared overlap of wave packets
evolving with two slightly different Hamiltonians) is a measure of quantum
reversibility. We investigate its behavior for classically quasi-integrable
systems. A dominant regime emerges where M(t) ~ t^{-alpha} with alpha=3d/2
depending solely on the dimension d of the system. This power law decay is
faster than the result ~ t^{-d} for the decay of classical phase space
densities
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