Three parallel algorithms for classical molecular dynamics are presented. The first assigns each processor a fixed subset of atoms; the second assigns each a fixed subset of inter-atomic forces to compute; the third assigns each a fixed spatial region. The algorithms are suitable for molecular dynamics models which can be difficult to parallelize efficiently—those with short-range forces where the neighbors of each atom change rapidly. They can be implemented on any distributed-memory parallel machine which allows for message-passing of data between independently executing processors. The algorithms are tested on a standard Lennard-Jones benchmark problem for system sizes ranging from 500 to 100,000,000 atoms on several parallel supercomputers--the nCUBE 2, Intel iPSC/860 and Paragon, and Cray T3D. Comparing the results to the fastest reported vectorized Cray Y-MP and C90 algorithm shows that the current generation of parallel machines is competitive with conventional vector supercomputers even for small problems. For large problems, the spatial algorithm achieves parallel efficiencies of 90% and a 1840-node Intel Paragon performs up to 165 faster than a single Cray C9O processor. Trade-offs between the three algorithms and guidelines for adapting them to more complex molecular dynamics simulations are also discussed.

Fast parallel algorithms for short-range molecular dynamics

다중혈관 관상동맥 환자에서 y-문합을 이용하여 양쪽 내흉동맥만을 사용한 우회술의 조기 성적

Natural gas hydrates are solid, non-stoichiometric compounds of small gas molecules and water. They form when the constituents come into contact at low temperature and high pressure. The physical properties of these compounds, most notably that they are non-flowing crystalline solids that are denser than typical fluid hydrocarbons and that the gas molecules they contain are effectively compressed, give rise to numerous applications in the broad areas of energy and climate effects. In particular, they have an important bearing on flow assurance and safety issues in oil and gas pipelines, they offer a largely unexploited means of energy recovery and transportation, and they could play a significant role in past and future climate change.

Fundamental principles and applications of natural gas hydrates

This chapter assesses long-term projections of climate change for the end of the 21st century and beyond, where the forced signal depends on the scenario and is typically larger than the internal variability of the climate system. Changes are expressed with respect to a baseline period of 1986-2005, unless otherwise stated.

Chapter 12 - Long-term climate change: Projections, commitments and irreversibility

OUTPU T 29 OUTPU T 30 OUTPU T 31 OUTPU T 32 OUTPU T 25 OUTPU T 26 OUTPU T 27 OUTPU T 28 OUTPU T 21 OUTPU T 22 OUTPU T 23 OUTPU T 24 OUTPU T 17 OUTPU T 18 OUTPU T 19 OUTPU T 20 OUTPU T 13 OUTPU T 14 OUTPU T 15 OUTPU T 16 OUTPU T 9 OUTPU T 10 OUTPU T 11 OUTPU T 12 OUTPU T 5 OUTPU T 6 OUTPU T 7 OUTPU T 8 OUTPU T 1 OUTPU T 2 OUTPU T 3 OUTPU T 4 29 30 31 32 25 26 27 28 21 22 23 24 17 18 19 20 13 14 15 16 9

A User’s Guide

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Numerical Studies on Two-way Coupled Fluid Flow and Geomechanics in Hydrate Deposits

EOS9nT is a new TOUGH2 module for the simulation of flow and transport of an arbitrary number n of tracers (solutes and/or colloids) in the subsurface The module first solves the flow-related equations, which are comprised of (a) the Richards equation and, depending on conditions, may also include (b) the flow equation of a dense brine or aqueous suspension and/or (c) the heat equation A second set of transport equations, corresponding to the n tracers, are then solved sequentially The low concentrations of the n tracers are considered to have no effect on the liquid phase, thus making possible the decoupling of their equations The first set of equations in EOS9nT provides the flow regime and account for fluid density variations due to thermal and/or solute concentration effects The n tracer transport equations account for sorption, radioactive decay, advection, hydrodynamic dispersion, molecular diffusion, as well as filtration (for colloids only) EOS9nT can handle gridblocks or irregular geometry in three-dimensional domains Preliminary results from four 1-D verification problems show an excellent agreement between the numerical predictions and the known analytical solutions

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EOS9nT: A TOUGH2 module for the Simulation of Flow and Solute/Colloid Transport

http://onepetro.org/OTCARCTIC/proceedings-pdf/doi/10.4043/22153-MS/1672285/otc-22153-ms.pdf

George J. Moridis

Papers

Numerical Studies on Two-way Coupled Fluid Flow and Geomechanics in Hydrate Deposits

EOS9nT: A TOUGH2 module for the Simulation of Flow and Solute/Colloid Transport

Simulation of Arctic Gas Hydrate Dissociation in Response to Climate Change: Basin-Scale Assessment

High Resolution Investigations of Flow and Thermal Processes During Production from Hydraulically Fractured Ultra-Low Permeability Media

Massively Parallel Simulation of Production from Oceanic Gas Hydrate Deposits