7,418 research outputs found
2D and 3D Dense-Fluid Shear Flows via Nonequilibrium Molecular Dynamics. Comparison of Time-and-Space-Averaged Tensor Temperature and Normal Stresses from Doll's, Sllod, and Boundary-Driven Shear Algorithms
Homogeneous shear flows (with constant strainrate du/dy) are generated with
the Doll's and Sllod algorithms and compared to corresponding inhomogeneous
boundary-driven flows. We use one-, two-, and three-dimensional smooth-particle
weight functions for computing instantaneous spatial averages. The nonlinear
stress differences are small, but significant, in both two and three space
dimensions. In homogeneous systems the sign and magnitude of the shearplane
stress difference, P(xx) - P(yy), depend on both the thermostat type and the
chosen shearflow algorithm. The Doll's and Sllod algorithms predict opposite
signs for this stress difference, with the Sllod approach definitely wrong, but
somewhat closer to the (boundary-driven) truth. Neither of the homogeneous
shear algorithms predicts the correct ordering of the kinetic temperatures,
T(xx) > T(zz) > T(yy).Comment: 34 pages with 12 figures, under consideration by Physical Review
Nonequilibrium Temperature and Thermometry in Heat-Conducting Phi-4 Models
We analyze temperature and thermometry for simple nonequilibrium
heat-conducting models. We show in detail, for both two- and three-dimensional
systems, that the ideal gas thermometer corresponds to the concept of a local
instantaneous mechanical kinetic temperature. For the Phi-4 models investigated
here the mechanical temperature closely approximates the local thermodynamic
equilibrium temperature. There is a significant difference between kinetic
temperature and the nonlocal configurational temperature. Neither obeys the
predictions of extended irreversible thermodynamics. Overall, we find that
kinetic temperature, as modeled and imposed by the Nos\'e-Hoover thermostats
developed in 1984, provides the simplest means for simulating, analyzing, and
understanding nonequilibrium heat flows.Comment: 20 pages with six figures, revised following review at Physical
Review
Microscopic and Macroscopic Stress with Gravitational and Rotational Forces
Many recent papers have questioned Irving and Kirkwood's atomistic expression
for stress. In Irving and Kirkwood's approach both interatomic forces and
atomic velocities contribute to stress. It is the velocity-dependent part that
has been disputed. To help clarify this situation we investigate [1] a fluid in
a gravitational field and [2] a steadily rotating solid. For both problems we
choose conditions where the two stress contributions, potential and kinetic,
are significant. The analytic force-balance solutions of both these problems
agree very well with a smooth-particle interpretation of the atomistic
Irving-Kirkwood stress tensor.Comment: Fifteen pages with seven figures, revised according to referees'
suggestions at Physical Review E. See also Liu and Qiu's arXiv contribution
0810.080
Cell module and fuel conditioner development
The design features and plans for fabrication of Stacks 564 and 800 are described. The results of the OS/IES loop testing of Stack 562, endurance testing of Stack 560 and the post test analysis of Stack 561 are reported. Progress on construction and modification of the fuel cell test facilities and the 10 kW reformer test station is described. Efforts to develop the technical data base for the fuel conditioning system included vendor contacts, packed bed heat transfer tests, development of the BOLTAR computer program, and work on the detailed design of the 10 kW reformer are described
Well-Posed Two-Temperature Constitutive Equations for Stable Dense Fluid Shockwaves using Molecular Dynamics and Generalizations of Navier-Stokes-Fourier Continuum Mechanics
Guided by molecular dynamics simulations, we generalize the
Navier-Stokes-Fourier constitutive equations and the continuum motion equations
to include both transverse and longitudinal temperatures. To do so we partition
the contributions of the heat transfer, the work done, and the heat flux vector
between the longitudinal and transverse temperatures. With shockwave boundary
conditions time-dependent solutions of these equations converge to give
stationary shockwave profiles. The profiles include anisotropic temperature and
can be fitted to molecular dynamics results, demonstrating the utility and
simplicity of a two-temperature description of far-from-equilibrium states.Comment: 19 pages with 10 figures, revised following review at Physical Review
E and with additional figure/discussion, for presentation at the
International Summer School and Conference "Advanced Problems in Mechanics"
[Saint Petersburg, Russia] 1-5 July 2010
Monetary and fiscal impacts on exchange rates
Foreign exchange rates ; Fiscal policy ; Monetary policy ; Budget deficits ; Dollar, American
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