Van der Waals model for confined fluids

Transforming variables in the double integral in Eq. (4.24) from ri,r2 to we have from the definition of Op ( ) 

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The study of fluid behavior in nano-confinement is a relatively new research arena. The ratio of surface area to volume becomes extremely large at such small scales in which the nondimensional Reynolds number Re is also typically low (<1) and the flow remains laminar. Diaguji et al. [4] mention that, except for steric interactions, intermolecular interactions like van der Waals force and electrostatic force can be modeled as continua. Specifically, the continuum dynanfics is an adequate description of liquid transport for length scales higher than 5 nm. In that context we... 

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