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Summary: Molecular Dynamics Study of the Effect of Atomic
Roughness on the Slip Length at the Fluid-Solid
Boundary during Shear Flow
T. M. Galea and Phil Attard*
School of Chemistry F11, University of Sydney NSW, 2006 Australia
Received October 8, 2003. In Final Form: February 2, 2004
A systematic study into the effect of solid roughness on the slip boundary condition during shear flow
is presented. Atomic roughness is modeled by varying the size and spacing between solid atoms at constant
packing fraction while the interaction parameters and the thermodynamic state of the fluid are kept
constant. It is shown that the fluid structure as manifest in the amplitude of the density oscillations
increases with increasing smoothness of the surfaces. The fluid-solid slip length is shown to exhibit
nonmonotonic behavior as the solid structure is varied from smooth to rough. Slip occurs for both smooth
and rough surfaces, and stick occurs only for surfaces commensurate with the fluid.
1. Introduction
The magnitude of the slip length at a fluid-solid
boundaryisofinteresttomanyfieldsofresearch,including
microfluidic devices, fluid flow in pores and in biological
systems, drainage flow between particles in mutual
motion, contact line motion of fluid interfaces, and friction
and wear in general. Hydrodynamics traditionally as-
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