1996 Fiscal Year Final Research Report Summary
Molecular Dynamics Study on Phase Change and Trans-Critical Phenomena of Fluids
| Project/Area Number |
07805021
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Thermal engineering
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| Research Institution | Tohoku University |
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Principal Investigator |
OHATA Taku Tohoku University, Institute of Fluid Science, Associate Professor, 流体科学研究所, 助教授 (40211833)
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| Co-Investigator(Kenkyū-buntansha) |
IMNAMI Yukio Tohoku University, Institute of Fluid Science, Research Associate, 流体科学研究所, 助手 (50271987)
UKAKU Motoyuki Tohoku University, Institute of Fluid Science, Research Associate, 流体化学研究所, 助手 (30006184)
AIHARA Toshio Tohoku University, Institute of Fluid Science, Professor, 流体科学研究所, 教授 (90006172)
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| Project Period (FY) |
1995 – 1996
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| Keywords | Molecular Dynamics / Phase and State Changes / Trans-critical Phenomena / Water / Hydrogen Bond / Simple Fluids / Structure in Fluids |
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| Research Abstract |
Main part of the present research is on the structural change in water in wide ranges of temperature and density. Molecular dynamics simulation has been performed for over 100 state points including liquid-vapor coexistence region, compressed liquid, near-and supercritical regions. Extensive analysis of the simulation results revealed the time-averaged characteristics of hydrogen bonds and their network (static structure of water) and their transient behaviors (dynamic structure).
Water structures at the liquid-vapor interface are important in the field of thermal engineering treating phase-change phenomena such as evaporation and condensation. To meet these requirement, we have performed MD simulation of liquid-vapor interface of water and analyzed the lifetime of hydrogen bonds and its connectivity to form networks.
To clarify basic characteristics of bulk fluid and liquid-vapor interface in the near-critical region, large-scale MD simulation has been performed for simple fluids modeled by the LJ potential. The abnormal behavior of thermophysical properties, such as specific heat at constant volume, near the critical point were analyzed and the result suggests that large-amplitude fluctuations in energy state are caused by the actively repeated formation and deformation of clusters. Results on the dynamic structure of water also revealed that stability of water cluster is minimized near the critical point. The analysis is still being performed to obtain some universal results from these observations.
Liquid-vapor interface at slightly sub-and supercritical pressure was analyzed and obtained the following results ; where temperature gradient exists in fluid, interface-like structure remains even in the supercritical fluid and simultaneously tension acting on the interface-like structure has a magnitude which is enough to influence the fluid motion. This results introduces a new insight concerning the boiling-like phenomena of near-critical fluid.
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