Publications (2)0 Total impact
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Article: Nonequilibrium molecular dynamics simulations of confined fluids in contact with the bulk
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ABSTRACT: A nonequilibrium molecular dynamics MD simulation study is reported of the structural and rheological properties of confined n-decane between two Au111 surfaces in contact with its bulk under constant normal loads or constant heights. In the constant-load MD simulations, it was observed that fluid molecules were squeezed out of the pore continuously in a single simulation upon compression, whereas fluid molecules in the bulk were soaked into the pore when applied normal load was released. Pore separation depends on bulk pressure under the same normal load and approaches a steady value as normal load increases. In the constant-height simulations, density, velocity, and orientational profiles of the confined film were accumulated along the Z perpendicular to the walls and Y parallel to the walls and finite due to the bulk directions. These distributions are not uniform not only along the Z direction but also along the Y direction, particularly for weak fluid–wall interactions. The shear-thinning behavior and ''slip'' boundary conditions were also studied in this work. Even though the shear-thinning behavior was reported by several previous studies, the number of particles was fixed and the bulk condition was unknown in those simulations. The simulation geometry employed in this work is closer to that of surface-force apparatus SFA experiments and of engine lubricating systems where confined liquid is in contact with its bulk. © 2001 American Institute of Physics. -
Article: Structural and rheological properties of n-decane confined between graphite surfaces
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ABSTRACT: We report a constant-volume and constant-pressure molecular dynamics study of the fluid structure, flow boundary condition, and shear viscosity of n-decane confined between graphite surfaces under various shear rates at 480 K using an anisotropic united atom model. The effect of surface corrugation, wall–fluid interaction strength, and load on these properties is investigated in this work. Our results show that the surface corrugation has a pronounced effect on rheological properties, but not on structural and orientational properties at the temperature studied. The shear thinning behavior of the confined fluids is observed for all cases under the shear rates studied. Our results also show that the velocity profile deviates more from the perfect linear profile with increasing surface corrugation, wall–fluid interaction strength, shear rate, and normal load. Slip occurs throughout the range of parameters studied. The fluid layers near the walls could be locked to each other even though slip occurs at the solid–fluid interface.Chemical Engineering Journal.
