Simulations of microlayer formation in nucleate boiling

Abstract

As a bubble grows outside of a cavity during nucleate boiling, viscous effects can be large enough compared to surface tension to impede liquid motion and trap a thin liquid layer, referred to as the microlayer, underneath the growing bubble. Numerical simulations of nucleate boiling typically resolve the macroscopic liquid-vapor interface of the bubble, but resort to subgrid models to account for micro scale effects, such as the evaporation of the microlayer. Evaporation models require initialization of the microlayer shape and extension, but models for microlayer formation are either physically incomplete or purely empirical. In this work, the Volume-Of-Fluid (VOF) method, implemented in the Gerris code, is used to numerically reproduce the hydrodynamics of hemispherical bubble growth at the wall, and resolve the formation of the microlayer with an unprecedented resolution. The simulations are validated against the latest experimental data and compared to existing analytical models. Lastly, remaining gaps in building a generally applicable model for the formation of the microlayer are presented.