58,371 research outputs found
Systematic Stochastic Reduction of Inertial Fluid-Structure Interactions subject to Thermal Fluctuations
We present analysis for the reduction of an inertial description of
fluid-structure interactions subject to thermal fluctuations. We show how the
viscous coupling between the immersed structures and the fluid can be
simplified in the regime where this coupling becomes increasingly strong. Many
descriptions in fluid mechanics and in the formulation of computational methods
account for fluid-structure interactions through viscous drag terms to transfer
momentum from the fluid to immersed structures. In the inertial regime, this
coupling often introduces a prohibitively small time-scale into the temporal
dynamics of the fluid-structure system. This is further exacerbated in the
presence of thermal fluctuations. We discuss here a systematic reduction
technique for the full inertial equations to obtain a simplified description
where this coupling term is eliminated. This approach also accounts for the
effective stochastic equations for the fluid-structure dynamics. The analysis
is based on use of the Infinitesmal Generator of the SPDEs and a singular
perturbation analysis of the Backward Kolomogorov PDEs. We also discuss the
physical motivations and interpretation of the obtained reduced description of
the fluid-structure system. Working paper currently under revision. Please
report any comments or issues to [email protected]: 19 pages, 1 figure. arXiv admin note: substantial text overlap with
arXiv:1009.564
GPU-accelerated simulation of colloidal suspensions with direct hydrodynamic interactions
Solvent-mediated hydrodynamic interactions between colloidal particles can
significantly alter their dynamics. We discuss the implementation of Stokesian
dynamics in leading approximation for streaming processors as provided by the
compute unified device architecture (CUDA) of recent graphics processors
(GPUs). Thereby, the simulation of explicit solvent particles is avoided and
hydrodynamic interactions can easily be accounted for in already available,
highly accelerated molecular dynamics simulations. Special emphasis is put on
efficient memory access and numerical stability. The algorithm is applied to
the periodic sedimentation of a cluster of four suspended particles. Finally,
we investigate the runtime performance of generic memory access patterns of
complexity for various GPU algorithms relying on either hardware cache
or shared memory.Comment: to appear in a special issue of Eur. Phys. J. Special Topics on
"Computer Simulations on GPUs
Genetic algorithm design of neural network and fuzzy logic controllers
Genetic algorithm design of neural network and fuzzy logic controller
Statistical Physics of Structural Glasses
This paper gives an introduction and brief overview of some of our recent
work on the equilibrium thermodynamics of glasses. We have focused onto first
principle computations in simple fragile glasses, starting from the two body
interatomic potential. A replica formulation translates this problem into that
of a gas of interacting molecules, each molecule being built of atoms, and
having a gyration radius (related to the cage size) which vanishes at zero
temperature. We use a small cage expansion, valid at low temperatures, which
allows to compute the cage size, the specific heat (which follows the Dulong
and Petit law), and the configurational entropy. The no-replica interpretation
of the computations is also briefly described. The results, particularly those
concerning the Kauzmann tempaerature and the configurational entropy, are
compared to recent numerical simulations.Comment: 21 pages, 6 figures, to appear in the proceedings of the Trieste
workshop on "Unifying Concepts in Glass Physics
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