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Slippage of viscoelastic fluids. The boundary condition.

Slippage of viscoelastic fluids. The boundary condition.

We just published an article on the slippage of complex fluides at the solid-liquid interface. Using a dynamic Surface Force Apparatus, we have demonstrated that the notion of slip length used to describe the boundary flow of simple liquids, is not appropriate for viscoelastic liquids. Rather, the appropriate description lies in the original Navier’s partial slip boundary condition, formulated in terms of an interfacial friction coefficient. We established an exact analytical expression to extract the interfacial friction coefficient from oscillatory drainage forces between a sphere and a plane, suitable for dynamic SFA or Atomic Force Microscopy non-contact measurements.

We have used this model to investigate the boundary friction of viscoelastic polymer solutions over 5 decades of film thicknesses and one decade in frequency. The proper use of the original Navier’s condition describes accurately the complex hydrodynamic force up to scales of tens of micrometers, with a simple "Newtonian-like" friction coefficient, not frequency dependent, and reflecting closely the dynamics of an interfacial depletion layer at the solution/solid interface.

This paper has been considered has a "Choice of the editor" for his novelty and broad interest.

Phys. Rev. Fluids: