1,361 research outputs found
Duality in matrix lattice Boltzmann models
The notion of duality between the hydrodynamic and kinetic (ghost) variables
of lattice kinetic formulations of the Boltzmann equation is introduced. It is
suggested that this notion can serve as a guideline in the design of matrix
versions of the lattice Boltzmann equation in a physically transparent and
computationally efficient way.Comment: 12 pages, 3 figure
Towards a mesoscopic model of water-like fluids with hydrodynamic interactions
We present a mesoscopic lattice model for non-ideal fluid flows with
directional interactions, mimicking the effects of hydrogen-bonds in water. The
model supports a rich and complex structural dynamics of the orientational
order parameter, and exhibits the formation of disordered domains whose size
and shape depend on the relative strength of directional order and thermal
diffusivity. By letting the directional forces carry an inverse density
dependence, the model is able to display a correlation between ordered domains
and low density regions, reflecting the idea of water as a denser liquid in the
disordered state than in the ordered one
Short-lived lattice quasiparticles for strongly interacting fluids
It is shown that lattice kinetic theory based on short-lived quasiparticles
proves very effective in simulating the complex dynamics of strongly
interacting fluids (SIF). In particular, it is pointed out that the shear
viscosity of lattice fluids is the sum of two contributions, one due to the
usual interactions between particles (collision viscosity) and the other due to
the interaction with the discrete lattice (propagation viscosity). Since the
latter is {\it negative}, the sum may turn out to be orders of magnitude
smaller than each of the two contributions separately, thus providing a
mechanism to access SIF regimes at ordinary values of the collisional
viscosity. This concept, as applied to quantum superfluids in one-dimensional
optical lattices, is shown to reproduce shear viscosities consistent with the
AdS-CFT holographic bound on the viscosity/entropy ratio. This shows that
lattice kinetic theory continues to hold for strongly coupled hydrodynamic
regimes where continuum kinetic theory may no longer be applicable.Comment: 10 pages, 2 figure
Nanoflows through disordered media: a joint Lattice Boltzmann and Molecular Dynamics investigation
We investigate nanoflows through dilute disordered media by means of joint
lattice Boltzmann (LB) and molecular dynamics (MD) simulations -- when the size
of the obstacles is comparable to the size of the flowing particles -- for
randomly located spheres and for a correlated particle-gel. In both cases at
sufficiently low solid fraction, , LB and MD provide similar values
of the permeability. However, for , MD shows that molecular size
effects lead to a decrease of the permeability, as compared to the
Navier-Stokes predictions. For gels, the simulations highlights a surplus of
permeability, which can be accommodated within a rescaling of the effective
radius of the gel monomers.Comment: 4 pages, 4 figure
A lattice Boltzmann study of reactive microflows
The role of geometrical micro-barriers on the conversion efficiency of
reactive flows in narrow three-dimensional channels of millimetric size is
investigated. Using a Lattice-Boltzmann-Lax-Wendroff code, we show that
micro-barriers have an appreciable effect on the effective reaction efficiency
of the device. If extrapolated to macroscopic scales, these effects can result
in a sizeable increase of the overall reaction efficiency.Comment: 5 pages, 7 figure
A lattice Boltzmann study of non-hydrodynamic effects in shell models of turbulence
A lattice Boltzmann scheme simulating the dynamics of shell models of
turbulence is developed. The influence of high order kinetic modes (ghosts) on
the dissipative properties of turbulence dynamics is studied. It is
analytically found that when ghost fields relax on the same time scale as the
hydrodynamic ones, their major effect is a net enhancement of the fluid
viscosity. The bare fluid viscosity is recovered by letting ghost fields evolve
on a much longer time scale. Analytical results are borne out by
high-resolution numerical simulations. These simulations indicate that the
hydrodynamic manifold is very robust towards large fluctuations of non
hydrodynamic fields.Comment: 17 pages, 3 figures, submitted to Physica
Lattice Boltzmann versus Molecular Dynamics simulation of nano-hydrodynamic flows
A fluid flow in a simple dense liquid, passing an obstacle in a
two-dimensional thin film geometry, is simulated by Molecular Dynamics (MD)
computer simulation and compared to results of Lattice Boltzmann (LB)
simulations. By the appropriate mapping of length and time units from LB to MD,
the velocity field as obtained from MD is quantitatively reproduced by LB. The
implications of this finding for prospective LB-MD multiscale applications are
discussed.Comment: 4 pages, 4 figure
Anisotropic imbibition on surfaces patterned with polygonal posts
We present and interpret lattice Boltzmann simulations of thick films
spreading on surfaces patterned with polygonal posts. We show that the
mechanism of pinning and depinning differs with the direction of advance, and
demonstrate that this leads to anisotropic spreading within a certain range of
material contact angles.Comment: DSFD Proceedings 201
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