9,547 research outputs found
Improved three-dimensional color-gradient lattice Boltzmann model for immiscible multiphase flows
In this paper, an improved three-dimensional color-gradient lattice Boltzmann
(LB) model is proposed for simulating immiscible multiphase flows. Compared
with the previous three-dimensional color-gradient LB models, which suffer from
the lack of Galilean invariance and considerable numerical errors in many cases
owing to the error terms in the recovered macroscopic equations, the present
model eliminates the error terms and therefore improves the numerical accuracy
and enhances the Galilean invariance. To validate the proposed model, numerical
simulation are performed. First, the test of a moving droplet in a uniform flow
field is employed to verify the Galilean invariance of the improved model.
Subsequently, numerical simulations are carried out for the layered two-phase
flow and three-dimensional Rayleigh-Taylor instability. It is shown that, using
the improved model, the numerical accuracy can be significantly improved in
comparison with the color-gradient LB model without the improvements. Finally,
the capability of the improved color-gradient LB model for simulating dynamic
multiphase flows at a relatively large density ratio is demonstrated via the
simulation of droplet impact on a solid surface.Comment: 9 Figure
Chemical turbulence equivalent to Nikolavskii turbulence
We find evidence that a certain class of reaction-diffusion systems can
exhibit chemical turbulence equivalent to Nikolaevskii turbulence. The
distinctive characteristic of this type of turbulence is that it results from
the interaction of weakly stable long-wavelength modes and unstable
short-wavelength modes. We indirectly study this class of reaction-diffusion
systems by considering an extended complex Ginzburg-Landau (CGL) equation that
was previously derived from this class of reaction-diffusion systems. First, we
show numerically that the power spectrum of this CGL equation in a particular
regime is qualitatively quite similar to that of the Nikolaevskii equation.
Then, we demonstrate that the Nikolaevskii equation can in fact be obtained
from this CGL equation through a phase reduction procedure applied in the
neighborhood of a codimension-two Turing--Benjamin-Feir point.Comment: 10 pages, 3 figure
Kaleidoscope of exotic quantum phases in a frustrated XY model
The existence of quantum spin liquids was first conjectured by Pomeranchuk
some 70 years ago, who argued that frustration in simple antiferromagnetic
theories could result in a Fermi-liquid-like state for spinon excitations. Here
we show that a simple quantum spin model on a honeycomb lattice hosts the long
sought for Bose metal with a clearly identifiable Bose surface. The complete
phase diagram of the model is determined via exact diagonalization and is shown
to include four distinct phases separated by three quantum phase transitions
- …