Computational modelling of Leidenfrost drops

Abstract

The Leidenfrost effect, where a drop levitates on a vapour film above a hot solid, is simulated using an efficient computational model that captures the internal flow within the droplet, models the vapour flow in a lubrication framework and is capable of resolving the dynamics of the process. The initial focus is on quasi-static droplets and the associated geometry of the vapour film formed beneath the drop, where we are able to compare with experimental analyses and assess the range of validity of the theoretical model developed in Sobac et al. (Phys. Rev. E, vol. 103, 2021, 039901). The computational model also allows us to explore parameter space, varying both the drop size and viscosity of the liquid, with computational results in excellent agreement with the theoretical model for high-viscosity liquids. Interestingly, for large water drops, discrepancies between the computational model and experiments occur, and possible reasons for this observation are provided. Our predictions reveal features including a regime with a dimpleless bottom surface of the drop and a minimum in the vapour layer thickness as a function of the drop size. Finally, the capability to simulate dynamics is revealed by computations that predict and track the vapour 'chimney' instability for large drops.