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Bouncing bubbles do not show water slip on smooth hydrophobic surfaces
Ivan U Vakarelski1, Farrukh Kamoliddinov2, Sigurdur T Thoroddsen2
1Division of Physical Sciences and Engineering, King Abdullah University of Science and Technology (KAUST), Thuwal 23955-6900, Saudi Arabia; Department of Chemical and Pharmaceutical Engineering, Faculty of Chemistry and Pharmacy, Sofia University, 1 James Bourchier Avenue, 1164 Sofia, Bulgaria.
Journal of Colloid and Interface Science
|December 29, 2024
Summary
Water does not slip on smooth hydrophobic surfaces, contrary to previous interpretations. Experiments and simulations confirm a no-slip boundary condition, challenging existing theories on hydrodynamic slip.
Area of Science:
- Fluid Dynamics
- Surface Science
- Hydrophobicity
Background:
- The existence of hydrodynamic slip on smooth hydrophobic surfaces remains a contentious topic in fluid dynamics.
- Previous experiments suggested significant water slip on these surfaces based on bubble bounce dynamics.
Purpose of the Study:
- To experimentally and numerically investigate the hydrodynamic behavior of water at smooth hydrophobic surfaces.
- To resolve the debate surrounding water slip on smooth hydrophobic surfaces.
Main Methods:
- Comparative experiments using millimeter-sized bubbles bouncing from smooth hydrophobic (graphite, Teflon) and hydrophilic (glass, mica) surfaces in pure water.
- Numerical simulations comparing bubble bounce from no-slip and free-slip walls.
Main Results:
- Bubble bounce dynamics were identical on both hydrophobic and hydrophilic surfaces.
- Experimental results closely matched numerical simulations of a no-slip wall.
- Simulations of a free-slip wall predicted significantly stronger bubble bouncing amplitudes.
Conclusions:
- The no-slip boundary condition for water on smooth hydrophobic surfaces is confirmed.
- The study refutes the interpretation of stronger bubble bounce as evidence for hydrodynamic slip.
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