Multiscale approach to model steady meniscus evaporation in a wetting fluid

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Department of Mechanical Engineering-Engineering Mechanics


Evaporation along a curved liquid vapor interface, such as that of a wetting meniscus, is a classic multiscale problem of vital significance to many fields of science and engineering. However, a complete description of the local evaporative flux over all length scales, especially without arbitrary tuning of boundary conditions, is lacking. A multiscale method to model evaporation from steady meniscus is described such that a need for tuning of boundary conditions and additional assumptions are alleviated. A meniscus submodel is used to compute evaporation flux in the bulk meniscus while a transition film submodel is used to account for enhanced evaporation near the contact line. A unique coupling between the meniscus and transition film submodels ensures smooth continuity of both film and mass flux profiles along the meniscus. The local mass flux is then integrated over the interfacial area to investigate the contribution from the different regions on the surface. The model is evaluated with data from cryoneutron phase-change tests conducted previously at National Institute for Standards and Technology (NIST) [K. Bellur et al., Cryogenics 74, 131 (2016)]. It is found that the peak mass flux in the transition region is two orders of magnitude greater than the flux at the apex. Despite the enhanced evaporation in the thin film region, it was found that 78–95% of the evaporation occurs in the bulk meniscus due to the large area. The bulk meniscus contribution increases with increase in vapor pressure and Bond number but decreases with an increase in thermal conductivity of the substrate. Using a nonuniform temperature boundary suggests that there is a possibility that the adsorbed film may have a nonzero mass flux.

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Physical Review Fluids