4,772 research outputs found
Employing per-component time step in DSMC simulations of disparate mass and cross-section gas mixtures
A new approach to simulation of stationary flows by Direct Simulation Monte
Carlo method is proposed. The idea is to specify an individual time step for
each component of a gas mixture. The approach consists of modifications mainly
to collision phase and recommendation on choosing time step ratios. It allows
softening the demands on the computational resources for cases of disparate
collision diameters of molecules and/or disparate molecular masses. These are
the cases important in vacuum deposition technologies. Few tests of the new
approach are made. Finally, the usage of new approach is demonstrated on a
problem of silver nanocluster diffusion in carrier gas argon in conditions of
silver deposition experiments.Comment: The goal of submission is to find native English speaker willing to
help me polish the paper. This is paper draft sent to Communications in
Computational Physics. It is recommended to publication. The need of
polishing was one of editors decision. See Additional data for MS Word source
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On the compatible weakly-nonlocal Poisson brackets of Hydrodynamic Type
We consider the pairs of general weakly non-local Poisson brackets of
Hydrodynamic Type (Ferapontov brackets) and the corresponding integrable
hierarchies. We show that under the requirement of non-degeneracy of the
corresponding "first" pseudo-Riemannian metric and also some
non-degeneracy requirement for the nonlocal part it is possible to introduce a
"canonical" set of "integrable hierarchies" based on the Casimirs, Momentum
functional and some "Canonical Hamiltonian functions". We prove also that all
the "Higher" "positive" Hamiltonian operators and the "negative" symplectic
forms have the weakly non-local form in this case. The same result is also true
for "negative" Hamiltonian operators and "positive" Symplectic structures in
the case when both pseudo-Riemannian metrics and
are non-degenerate.Comment: 31 Pages, Latex, reference adde
Whitham's Method and Dubrovin-Novikov Bracket in Single-Phase and Multiphase Cases
In this paper we examine in detail the procedure of averaging of the local
field-theoretic Poisson brackets proposed by B.A. Dubrovin and S.P. Novikov for
the method of Whitham. The main attention is paid to the questions of
justification and the conditions of applicability of the Dubrovin-Novikov
procedure. Separate consideration is given to special features of single-phase
and multiphase cases. In particular, one of the main results is the
insensitivity of the procedure of bracket averaging to the appearance of
"resonances" which can arise in the multi-phase situation.Comment: 53 pages, extension to the multi-dimensional case is given in
arXiv:1211.575
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