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Jeffrey Yepez

Publications and source records attributed to Jeffrey Yepez.

24 records · Page 2Linked to original sources
arXiv2002

Galilean-Invariant Lattice-Boltzmann Models with H-Theorem

We demonstrate that the requirement of galilean invariance determines the choice of H function for a wide class of entropic lattice Boltzmann models for the incompressible Navier-Stokes equations. The required H function has the form of the Burg entropy for D=2, and of a Tsallis entropy with q=1-2/D for D>2, where D is the number of spatial dimensions. We use this observation to construct a fully explicit, unconditionally stable, galilean invariant, lattice-Boltzmann model for the incompressible Navier-Stokes equations, for which attainable Reynolds number is limited only by grid resolution.

cond-mat.stat-mech↗
arXiv2002

An efficient quantum algorithm for the one-dimensional Burgers equation

We analyze one-dimensional classical and quantum microscopic lattice-gas models governed by a lattice Boltzmann equation at the mesoscopic scale, achieved by ensemble averaging over microscopic realizations. The models are governed by the Burgers equation at the macroscopic scale, achieved by taking the limit where the grid size and time step both approach zero and by performing a perturbative Chapman-Enskog expansion. The quantum algorithm exploiting superposition and entanglement is more efficient than the classical one because the quantum algorithm requires less memory. Furthermore, its viscosity can be made arbitrarily small.

quant-ph↗
arXiv1996

Integer Lattice Gases

We generalize the hydrodynamic lattice gas model to include arbitrary numbers of particles moving in each lattice direction. For this generalization we derive the equilibrium distribution function and the hydrodynamic equations, including the equation of state and the prefactor of the inertial term that arises from the breaking of galilean invariance in these models. We show that this prefactor can be set to unity in the generalized model, therby effectively restoring galilean invariance. Moreover, we derive an expression for the kinematic viscosity, and show that it tends to decrease with the maximum number of particles allowed in each direction, so that higher Reynolds numbers may be achieved. Finally, we derive expressions for the statistical noise and the Boltzmann entropy of these models.

comp-gas↗
arXiv1994

Lattice-Gas Automata Fluids on Parallel Supercomputers

A condensed history and theoretical development of lattice-gas automata in the Boltzmann limit is presented. This is provided as background to set up the context for understanding the implementation of the lattice-gas method on two parallel supercomputers: the MIT cellular automata machine CAM-8 and the Connection Machine CM-5. The macroscopic limit of two-dimensional fluids is tested by simulating the Rayleigh-Bénard convective instability, Kelvin-Helmholtz shear instability, and the Von Karman vortex shedding instability. Performance of the two machines in terms of both site update rate and maximum problem size are comparable. The CAM-8, being a low-cost desktop machine, demonstrates the potential of special-purpose digital hardware.

comp-gas↗
arXiv1994

A Lattice-Gas with Long-Range Interactions Coupled to a Heat Bath

Introduced is a lattice-gas with long-range 2-body interactions. An effective inter-particle force is mediated by momentum exchanges. There exists the possibility of having both attractive and repulsive interactions using finite impact parameter collisions. There also exists an interesting possibility of coupling these long-range interactions to a heat bath. A fixed temperature heat bath induces a permanent net attractive interparticle potential, but at the expense of reversibility. Thus the long-range dynamics is a kind of a Monte Carlo Kawasaki updating scheme. The model has a $PρT$ equation of state. Presented are analytical and numerical results for the a lattice-gas fluid governed by a nonideal equation of state. The model's complexity is not much beyond that of the FHP lattice-gas. It is suitable for massively parallel processing and may be used to study critical phenomena in large systems.

comp-gas↗