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Effect of flow field and geometry on the dynamic contact angle
A V Lukyanov1, Y D Shikhmurzaev
1Department of Mathematics, University of Reading, Whiteknights, UK.
Summary
Dynamic contact angle in wetting depends on more than just speed. Flow field and geometry significantly influence wetting behavior, offering new ways to study liquid-solid interfaces.
Area of Science:
- Fluid Dynamics
- Surface Science
- Materials Science
Background:
- Recent experiments indicate dynamic contact angles are influenced by flow fields and geometry near the moving contact line.
- Dynamic wetting is viewed as a process of forming new liquid-solid interfaces, not an isolated problem.
- Existing slip models primarily consider wetting speed and material constants.
Purpose of the Study:
- To investigate the influence of flow field and geometry on dynamic contact angles within a theoretical framework.
- To analyze dynamic wetting in the specific context of curtain coating.
Main Methods:
- Theoretical analysis based on a general class of flows with forming/disappearing interfaces.
- Investigation of the curtain coating flow configuration.
Main Results:
- In curtain coating, dynamic contact angle depends on wetting speed, material properties, curtain inlet velocity, height, and impact angle.
- Flow field and geometry near the contact line can be manipulated to vary the dynamic contact angle at a constant wetting speed.
- Surface tensions at the contact line are influenced by flow field distributions.
Conclusions:
- Dynamic contact angle is a multiparametric signal sensitive to flow conditions and interfacial dynamics.
- This provides a macroscopic approach to experimentally probe interfacial properties like equation of state and rheology.
- Enables measurement of parameters such as sliding friction coefficient and surface-tension relaxation time.
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