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Published May 10, 2006 | public
Journal Article Open

Influence of periodic wall roughness on the slip behaviour at liquid/solid interfaces: molecular-scale simulations versus continuum predictions


The influence of surface roughness on the slip behaviour of a Newtonian liquid in steady planar shear is investigated using three different approaches, namely Stokes flow calculations, molecular dynamics (MD) simulations and a statistical mechanical model for the friction coefficient between a corrugated wall and the first liquid layer. These approaches are used to probe the behaviour of the slip length as a function of the slope parameter ka = 2πa/λ, where a and λ represent the amplitude and wavelength characterizing the periodic corrugation of the bounding surface. The molecular and continuum approaches both confirm a monotonic decay in the slip length with increasing ka but the rate of decay as well as the magnitude of the slip length obtained from the Stokes flow solutions exceed the MD predictions as the wall feature sizes approach the liquid molecular dimensions. In the limit of molecular-scale wall corrugation, a Green–Kubo analysis based on the fluctuation–dissipation theorem accurately reproduces the MD results for the behaviour of the slip length as a function of a. In combination, these three approaches provide a detailed picture of the influence of periodic roughness on the slip length which spans multiple length scales ranging from molecular to macroscopic dimensions.

Additional Information

© Cambridge University Press 2006. Reprinted with permission. (Received 27 July 2005 and in revised form 11 January 2006). Published online 24 April 2006 This work is supported by grants from the NASA Microgravity Fluid Physics program, the National Science Foundation – Sensor and Sensor Networks Program, and the US Army TACOM-ARDEC. S.M.T. also gratefully acknowledges the hospitality and financial support of the Moore Distinguished Scholar Program at the California Institute of Technology where this work was completed, as well as the Princeton University Computing Facility for use of the Beowulf cluster. Dr A. A. Darhuber kindly provided the data in figure 6(c).


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