Entropy increase in confined free expansions via molecular dynamics and smooth-particle applied mechanics
- Department of Applied Science, University of California at Davis/Livermore and Lawrence Livermore National Laboratory, Livermore, California 94551-7808 (United States)
- Institut fuer Experimentalphysik, Universitaet Wien, Boltzmanngasse 5, A-1090 Wien (Austria)
The eventual entropy increase of an ideal gas undergoing free expansion, {Delta}S=k&hthinsp;ln(V{sub fin}/V{sub 0}), requires a {open_quotes}coarse-grained{close_quotes} hydrodynamic description because Gibbs{close_quote} fine-grained entropy is unchanged in such a process. Smooth particle applied mechanics (SPAM) is well suited to the simulation and study of such problems because the particles in SPAM simulations can be of any size, from microscopic to macroscopic. SPAM furnishes a natural interpolation, or bridge, linking microscopic molecular dynamics to macroscopic continuum mechanics. We analyze particle-based simulations of ideal-gas free expansions from both the microscopic and the macroscopic points of view, comparing several dynamical estimates for the time development of the system entropy. Most of the entropy increase occurs rapidly, within a single sound traversal time. A local comoving version of turbulent hydrodynamics provides the most useful viewpoint for describing flows of this kind. {copyright} {ital 1999} {ital The American Physical Society}
- OSTI ID:
- 308256
- Journal Information:
- Physical Review. E, Statistical Physics, Plasmas, Fluids, and Related Interdisciplinary Topics, Vol. 59, Issue 2; Other Information: PBD: Feb 1999
- Country of Publication:
- United States
- Language:
- English
Similar Records
Algorithmic randomness and physical entropy
Intrinsic instability and entropy stabilization of grain boundaries