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ARTICLE

Molecular Dynamics Analysis of the Vaporization Process for Two Nano-Scale Liquid Threads Coexisting in a Periodic Fundamental Cell

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1 Department of Aeronautical Engineering, National Formosa University, Huwei, Yunlin 632, Taiwan, R.O.C. Tel. No.: 886-5-6315527, Fax No.: 886-5-6312415, E-mail: clyeh@nfu.edu.tw

Computer Modeling in Engineering & Sciences 2010, 67(3), 175-210. https://doi.org/10.3970/cmes.2010.067.175

Abstract

Previous studies of nano-scale liquid threads have almost entirely been devoted to the investigation of a single liquid thread in a periodic fundamental cell. This paper is the first to study the vaporization process of two nano-scale liquid threads coexisting in a periodic fundamental cell by molecular dynamics (MD) simulation. Because of the interaction between the two liquid threads, the vaporization process is different from that of a single liquid thread in a periodic fundamental cell. This study discusses the influences of the liquid thread radius, fundamental cell length, and relative position of the two threads. Snapshots of molecules, the number of liquid particles formed, and density field are analyzed. Two linear stability criteria, namely, Rayleigh's stability criterion and Kim's stability criterion, are accessed for their validity in molecular scale. It is found that the two liquid threads may remain intact or evolve into only one liquid particle if the fundamental cell length is small. If the threads break up in this case, they rupture from their ends only, i.e. the top and bottom surfaces of the fundamental cell, but not from their interiors. On the other hand, if the fundamental cell length is larger, more than one liquid particle may be produced in the cell and the liquid threads rupture not only from their ends but also from their interiors. It is also found that thinner liquid threads may produce more liquid particles in the cell and evaporate more quickly. In addition, more liquid particles are formed when the separation of the two threads is larger. Moreover, vaporization is slower when the two liquid threads are close to each other. On the basis of identical liquid thread radius and length, liquid threads that produce more liquid particles evaporate more quickly. Finally, the trends of Rayleigh's stability criterion and Kim's stability criterion agree with MD simulation results. However, when the two threads coalesce into a single thread and remain intact, the critical wavelength of perturbation may be increased and the stable domain is broadened. Under such a situation, Rayleigh's stability criterion and Kim's stability criterion underpredict the stable domain.

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