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Effect of surface roughness on rate-dependent slip in simple fluids
1Department of Mechanical Engineering, Michigan State University, East Lansing, MI 48824, USA. priezjev@egr.msu.edu
The Journal of Chemical Physics
|October 16, 2007
Summary
Surface roughness significantly impacts liquid slip in thin films. Molecular dynamics simulations reveal that roughness reduces slip length and its dependence on shear rate, unlike smooth surfaces.
Area of Science:
- Physics
- Materials Science
- Surface Science
Background:
- Understanding liquid behavior at interfaces is crucial for microfluidics and lubrication.
- Surface properties, including roughness, significantly influence fluid dynamics at the nanoscale.
- Molecular dynamics (MD) simulations offer a powerful tool to probe these interfacial phenomena.
Purpose of the Study:
- To investigate the effect of molecular-scale surface roughness on slip behavior in thin liquid films.
- To elucidate the relationship between surface characteristics, shear rate, and slip length.
- To explore how wall properties like elastic stiffness and corrugation patterns affect slip.
Main Methods:
- Utilizing molecular dynamics (MD) simulations.
- Modeling thin liquid films confined between solid surfaces with varying degrees of roughness.
- Analyzing slip length as a function of shear rate under different surface conditions.
Main Results:
- For atomically smooth or incommensurate interfaces, slip length increases nearly linearly with shear rate.
- Effective surface roughness from thermal wall fluctuations weakens slip length's shear rate dependence.
- Increased wall elastic stiffness reduces roughness, restoring strong shear rate dependence.
- Both periodic and random surface corrugations decrease slip length and its shear rate dependence.
Conclusions:
- Molecular-scale surface roughness plays a critical role in modulating slip behavior in thin liquid films.
- Surface topography and material properties (elastic stiffness) are key determinants of slip length and its shear rate dependency.
- MD simulations provide valuable insights into the complex interplay between surface structure and fluid slip at the nanoscale.
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