31 research outputs found
Lattice Boltzmann method with self-consistent thermo-hydrodynamic equilibria
Lattice kinetic equations incorporating the effects of external/internal
force fields via a shift of the local fields in the local equilibria, are
placed within the framework of continuum kinetic theory. The mathematical
treatment reveals that, in order to be consistent with the correct
thermo-hydrodynamical description, temperature must also be shifted, besides
momentum. New perspectives for the formulation of thermo-hydrodynamic lattice
kinetic models of non-ideal fluids are then envisaged. It is also shown that on
the lattice, the definition of the macroscopic temperature requires the
inclusion of new terms directly related to discrete effects. The theoretical
treatment is tested against a controlled case with a non ideal equation of
state.Comment: 10 pages, 1 figur
Numerical simulations of compressible Rayleigh-Taylor turbulence in stratified fluids
We present results from numerical simulations of Rayleigh-Taylor turbulence,
performed using a recently proposed lattice Boltzmann method able to describe
consistently a thermal compressible flow subject to an external forcing. The
method allowed us to study the system both in the nearly-Boussinesq and
strongly compressible regimes. Moreover, we show that when the stratification
is important, the presence of the adiabatic gradient causes the arrest of the
mixing process.Comment: 15 pages, 11 figures. Proceedings of II Conference on Turbulent
Mixing and Beyond (TMB-2009
Permeability of self-affine rough fractures
The permeability of two-dimensional fractures with self-affine fractal
roughness is studied via analytic arguments and numerical simulations. The
limit where the roughness amplitude is small compared with average fracture
aperture is analyzed by a perturbation method, while in the opposite case of
narrow aperture, we use heuristic arguments based on lubrication theory.
Numerical simulations, using the lattice Boltzmann method, are used to examine
the complete range of aperture sizes, and confirm the analytic arguments.Comment: 11 pages, 9 figure
Simulation of Flow of Mixtures Through Anisotropic Porous Media using a Lattice Boltzmann Model
We propose a description for transient penetration simulations of miscible
and immiscible fluid mixtures into anisotropic porous media, using the lattice
Boltzmann (LB) method. Our model incorporates hydrodynamic flow, diffusion,
surface tension, and the possibility for global and local viscosity variations
to consider various types of hardening fluids. The miscible mixture consists of
two fluids, one governed by the hydrodynamic equations and one by diffusion
equations. We validate our model on standard problems like Poiseuille flow, the
collision of a drop with an impermeable, hydrophobic interface and the
deformation of the fluid due to surface tension forces. To demonstrate the
applicability to complex geometries, we simulate the invasion process of
mixtures into wood spruce samples.Comment: Submitted to EPJ
The structure of (SCN)<sub>x</sub>. A study using molecular and solid state density functional theory calculations
Molecular fragments and crystal structures based on proposed structures for polythiocyanogen were studied using molecular and solid-state electronic structure calculations at the density functional theory level. The energetics and chemical shifts from both types of calculations indicate that a planar N-linked chain consisting of 1,2,4-dithiazole five-rings with adjacent rings pointing in opposite directions is the most likely local structure of the (SCN)x polymer