We numerically probe the transient evaporation dynamics of wettability influenced capillary bridges. For this purpose, first the profile of capillary surface is numerically obtained using Level Set (LS) method. Then this profile is used as input for the transient evaporation model. The corresponding governing differential equations for mass, momentum, and energy transfer are solved in a fully coupled manner based on Arbitrary Lagrangian–Eulerian (ALE) framework. We vary the contact angles at solid–liquid interface over a wide range to portray the role of wetting state on evaporation kinetics. Results show that, large contact angles manifest upscaled mass loss rate due to alleviated vapor confinement effect around the capillary surface. During the initial transient regime, the interfacial temperature evolves in a non-linear manner due to internal heat advection. This leads to formation of multi-vortex pattern during initial stages. Also, the evaporative mass flux for large contact angles (low wetting conditions) is significantly higher near the bulge region. As a result, the evaporation-induced cooling and the corresponding internal velocity scales are significantly amplified in such cases than the hydrophilic surfaces. This upscaled internal velocity facilitates the temperature homogenization process thereby causing the stable conditions to be reached at much early stages than high wetting conditions.

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Substrate Wettability Influenced Evaporative Thermo-Fluid Dynamics of Capillary Bridges

  • Arnov Paul,
  • Apurba Roy,
  • Purbarun Dhar

摘要

We numerically probe the transient evaporation dynamics of wettability influenced capillary bridges. For this purpose, first the profile of capillary surface is numerically obtained using Level Set (LS) method. Then this profile is used as input for the transient evaporation model. The corresponding governing differential equations for mass, momentum, and energy transfer are solved in a fully coupled manner based on Arbitrary Lagrangian–Eulerian (ALE) framework. We vary the contact angles at solid–liquid interface over a wide range to portray the role of wetting state on evaporation kinetics. Results show that, large contact angles manifest upscaled mass loss rate due to alleviated vapor confinement effect around the capillary surface. During the initial transient regime, the interfacial temperature evolves in a non-linear manner due to internal heat advection. This leads to formation of multi-vortex pattern during initial stages. Also, the evaporative mass flux for large contact angles (low wetting conditions) is significantly higher near the bulge region. As a result, the evaporation-induced cooling and the corresponding internal velocity scales are significantly amplified in such cases than the hydrophilic surfaces. This upscaled internal velocity facilitates the temperature homogenization process thereby causing the stable conditions to be reached at much early stages than high wetting conditions.