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

Gas hydrates have received considerable attention due to their important role in flow assurance for the oil and gas industry, their extensive natural occurrence on Earth and extraterrestrial planets, and their significant applications in sustainable technologies including but not limited to gas and energy storage, gas separation, and water desalination Given not only their inherent structural flexibility depending on the type of guest gas molecules and formation conditions, but also the synthetic effects of a wide range of chemical additives on their properties, these variabilities could be exploited to optimise the role of gas hydrates This includes increasing their industrial applications, understanding and utilising their role in Nature, identifying potential methods for safely extracting natural gases stored in naturally occurring hydrates within the Earth, and for developing green technologies This review summarizes the different properties of gas hydrates as well as their formation and dissociation kinetics and then reviews the fast-growing literature reporting their role and applications in the aforementioned fields, mainly concentrating on advances during the last decade Challenges, limitations, and future perspectives of each field are briefly discussed The overall objective of this review is to provide readers with an extensive overview of gas hydrates that we hope will stimulate further work on this riveting field

Gas hydrates in sustainable chemistry

A review on the role and impact of various additives as promoters/ inhibitors for gas hydrate formation

Natural gas hydrates (NGH) are prone to causing pipeline blockage in flow assurance, attracting considerable attention in the petroleum industry. This work reviews the significant progress in hydra...

Status of Natural Gas Hydrate Flow Assurance Research in China: A Review

With the exploration and development of natural gas gradually extended to the deep sea, low-temperature and high-pressure environmental conditions and long-distance transportation make flow assurance engineers have to consider the impact of the formation and blockage of natural gas hydrates on the flow stability in the pipeline. Therefore, an inadequate understanding of the hydrate formation and plugging mechanism in a gas-rich (gas-dominant) system has become a serious obstacle to the prediction of hydrate formation and implementation of blocking prevention and control strategies. To this end, this review has conducted a comprehensive review of recent experimental investigations into hydrate formation and blockage in gas-rich systems in flow loop devices, and the physical models to characterize the clogging mechanism of hydrates established by previous scholars were summarized. In addition, the three flow patterns of the gas-rich system were divided, and the hydrate deposition mechanism corresponding to each flow pattern and the prediction model of the deposition layer thickness was summarized. Eventually, the natural gas hydrate mitigation and prophylaxis and restrain strategies used in the process of deep-sea natural gas transportation were summarized, including advantages and disadvantages of natural gas dehydration, changing the gas flow rate, and adding chemical inhibitors. The advantages and feasibility of an under-inhibited system and changing the gas flow rate for the management and prevention of hydrate blockage were emphasized. The conclusion can improve the safety index of natural gas development and transportation operations and reduce the output loss of natural gas energy and economic loss of hydrate anti-blocking. 

Hydrate Deposition Model and Flow Assurance Technology in Gas-Dominant Pipeline Transportation Systems: A Review

Molecular dynamics simulation to explore the synergistic inhibition effect of kinetic and thermodynamic hydrate inhibitors

The invalidation mechanism of kinetic hydrate inhibitors under high subcooling conditions

Experimental investigation on the spatial differences of hydrate dissociation by depressurization in water-saturated methane hydrate reservoirs

The effect of kinetic hydrate inhibitors (KHIs) on the growth of methane hydrate in the gas–liquid phase separation state is studied at the molecular level. The simulation results show that the kinetic inhibitors, named PVP and PVP-A, show good inhibitory effects on the growth of methane hydrate under the gas–liquid phase separation state, and the initial position of the kinetic hydrate inhibitors has a major effect on the growth of methane hydrates. In addition, inhibitors at different locations exhibit different inhibition performances. When the inhibitor molecules are located at the gas–liquid phase interface, increasing the contact area between the groups of the inhibitor molecules and methane is beneficial to enhance the inhibitory performance of the inhibitors. When inhibitor molecules are located at the solid–liquid phase interface, the inhibitor molecules adsorbed on the surface of the hydrate nucleus and decreased the direct contact of hydrate nucleus with the surrounding water and methane molecules, which would delay the growth of hydrate nucleus. Moreover, the increase of hydrate surface curvature and the Gibbs–Thomson effect caused by inhibitors can also reduce the growth rate of methane hydrate.

https://www.mdpi.com/1996-1073/12/23/4482/pdf

Liwei Cheng

Papers

Molecular dynamics simulation to explore the synergistic inhibition effect of kinetic and thermodynamic hydrate inhibitors

The invalidation mechanism of kinetic hydrate inhibitors under high subcooling conditions

Experimental investigation on the spatial differences of hydrate dissociation by depressurization in water-saturated methane hydrate reservoirs

Inhibition Effect of Kinetic Hydrate Inhibitors on the Growth of Methane Hydrate in Gas–Liquid Phase Separation State

Study on the spatial differences of methane hydrate dissociation process by depressurization using an L-shape simulator