11 results match your criteria: "Ruby Valley Research Institute[Affiliation]"
Entropy (Basel)
January 2022
Department of Mechanical and Aerospace Engineering, Brunel University London, Uxbridge UB8 3PH, UK.
Time-reversible dynamical simulations of nonequilibrium systems exemplify both Loschmidt's and Zermélo's paradoxes. That is, computational time-reversible simulations invariably produce solutions consistent with the Second Law of Thermodynamics (Loschmidt's) as well as in the time (Zermélo's, illustrating Poincaré recurrence). Understanding these paradoxical aspects of time-reversible systems is enhanced here by studying the simplest pair of such model systems.
View Article and Find Full Text PDFJ Chem Phys
September 2020
Ruby Valley Research Institute, Highway Contract 60, Box 601, Ruby Valley, Nevada 89833, USA.
J Chem Phys
August 2020
Ruby Valley Research Institute, Highway Contract 60, Box 601, Ruby Valley, Nevada 89833, USA.
This is our current research perspective on models providing insight into statistical mechanics. It is necessarily personal, emphasizing our own interest in simulation as it developed from the National Laboratories' work to the worldwide explosion of computation of today. We contrast the past and present in atomistic simulations, emphasizing those simple models that best achieve reproducibility and promote understanding.
View Article and Find Full Text PDFPhys Rev E Stat Nonlin Soft Matter Phys
April 2014
Ruby Valley Research Institute, Highway Contract 60, Box 601, Ruby Valley, Nevada 89833, USA.
We use nonequilibrium molecular dynamics to analyze and illustrate the qualitative differences between the one-thermostat and two-thermostat versions of equilibrium and nonequilibrium (heat-conducting) harmonic oscillators. Conservative nonconducting regions can coexist with dissipative heat conducting regions in phase space with exactly the same imposed temperature field.
View Article and Find Full Text PDFPhys Rev Lett
April 2014
Immobilisation Science Laboratory, Department of Materials Science and Engineering, University of Sheffield, Mappin Street, Sheffield S1 3JD, United Kingdom.
Structurally stable atomistic one-dimensional shock waves have long been simulated by injecting fresh cool particles and extracting old hot particles at opposite ends of a simulation box. The resulting shock profiles demonstrate tensor temperature, Txx≠Tyy and Maxwell's delayed response, with stress lagging strain rate and heat flux lagging temperature gradient. Here this same geometry, supplemented by a short-ranged external "plug" field, is used to simulate steady Joule-Kelvin throttling flow of hot dense fluid through a porous plug, producing a dilute and cooler product fluid.
View Article and Find Full Text PDFPhys Rev E Stat Nonlin Soft Matter Phys
April 2010
Ruby Valley Research Institute, Highway Contract 60, Box 598, Ruby Valley, 89833 Nevada, USA.
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.
View Article and Find Full Text PDFPhys Rev E Stat Nonlin Soft Matter Phys
July 2009
Ruby Valley Research Institute, Highway Contract 60, Box 598, Ruby Valley, Nevada 89833, USA.
The anisotropy of temperature is studied here in a strong two-dimensional shock wave, simulated with conventional molecular dynamics. Several forms of the kinetic temperature are considered, corresponding to different choices for the local instantaneous stream velocity. A local particle-based definition omitting any "self"-contribution to the stream velocity gives the best results.
View Article and Find Full Text PDFPhys Rev E Stat Nonlin Soft Matter Phys
April 2009
Ruby Valley Research Institute, Highway Contract 60, Ruby Valley, Nevada 89833, USA.
We compare nonlinear stresses and temperatures for adiabatic-shear flows, using up to 262, 144 particles, with those from corresponding homogeneous and inhomogeneous flows. Two varieties of kinetic temperature tensors are compared to the configurational temperatures. This comparison of temperatures led us to two findings beyond our original goal of analyzing shear algorithms.
View Article and Find Full Text PDFPhys Rev E Stat Nonlin Soft Matter Phys
March 2009
Ruby Valley Research Institute, Highway Contract 60, Box 598, Ruby Valley, Nevada 89833, USA.
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.
View Article and Find Full Text PDFPhys Rev E Stat Nonlin Soft Matter Phys
October 2008
Ruby Valley Research Institute, Highway Contract 60, Box 598, Ruby Valley, Nevada 89833, USA.
Homogeneous shear flows (with constant strainrate dv(x)/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 normal-stress differences are small, but significant, in both two and three space dimensions.
View Article and Find Full Text PDFPhys Rev E Stat Nonlin Soft Matter Phys
April 2008
Ruby Valley Research Institute, Highway Contract 60, Box 598 Ruby Valley, Nevada 89833, USA.
We analyze temperature and thermometry for simple nonequilibrium heat-conducting models. We also 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 phi4 models investigated here the mechanical temperature closely approximates the local thermodynamic equilibrium temperature.
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