Complex transition pathways in boiling and cavitation

This work combines Navier–Stokes–Korteweg dynamics and rare event techniques to investigate the transition pathways and times of vapour bubble nucleation in metastable liquids under homogeneous and heterogeneous conditions. The nucleation pathways deviate from classical theory, showing that bubble volume alone is an inadequate reaction coordinate. The nucleation mechanism is driven by long-wavelength fluctuations with densities slightly different from the metastable liquid. We propose a new strategy to evaluate the typical nucleation times by inferring the diffusion coefficients from hydrodynamics. The methodology is validated against state-of-the-art nucleation theories in homogeneous conditions, revealing non-trivial, significant effects of surface wettability on heterogeneous nucleation. Notably, homogeneous nucleation is detected at moderate hydrophilic wettabilities despite the presence of a wall, an effect not captured by classical theories but consistent with atomistic simulations. Hydrophobic surfaces, instead, anticipate the spinodal. The proposed approach is fairly general and, despite the paper discussing results for a prototypical fluid, it can be easily extended, also in complex geometries, to any real fluid provided the equation of state is available, paving the way to model complex nucleation problems in real systems.