Abstract

Vapour bubbles form in liquids by two main mechanisms: boiling, by increasing the temperature over the boiling threshold, and cavitation, by reducing the pressure below the vapour pressure threshold. The precise identification of these thermodynamic limits is a daunting task. Liquids can be held in metastable states (overheating and tensile conditions, respectively) for a long time without forming bubbles. Bubble nucleation is indeed an activated process, requiring a certain amount of energy to overcome the free energy barrier and bring the liquid from the metastable conditions to the thermodynamically stable (vapour) state. Nowadays molecular dynamics is the unique tool to investigate such thermally activated processes. However, its computational cost limits its application to small systems (less than a few tenths of nanometers) and to very short times, preventing the study of hydrodynamics and thermal transport processes. In this talk, I will present a novel model based on diffuse interface thermodynamics and fluctuating hydrodynamics, which enables a holistic description of liquid/vapour phase transitions from nucleation to hydrodynamic motion [1-3].  I will present results concerning both the cavitation and boiling process, focusing on the role of heterogeneous nucleation in lowering transition thermodynamic limits [4]. Finally, I will discuss the possibility of describing liquid/vapour phase change by leveraging rare event techniques borrowed from statistical physics, taking the boiling of liquid nitrogen and the cavitation in pure water as study cases. 

1) Gallo, M., et al.  “Thermally activated vapor bubble nucleation: the Landau-Lifshitz/Van der Waals approach”. Physical Review Fluids 2018. 

2) Gallo, M. et al.   “Nucleation and Growth dynamics of vapor bubbles”. Journal of Fluid Mechanics 2020.   

3) Gallo, M. et al.    “Heterogeneous bubble nucleation dynamics”. Journal of Fluid Mechanics  2021.

4) Gallo, M. et al.  “A nanoscale view of the origin of boiling and its dynamics”.  Nature  Communications 2023.

Biography

Mirko Gallo is a Researcher in Fluid Mechanics at the department of Mechanical and Aerospace engineering at Sapienza University of Rome (IT). Previously, he was a postdoc in the same department and a research fellow at the Advanced Engineering Centre at the University of Brighton (UK).  He received his PhD in Theoretical and Applied Mechanics at Sapienza University of Rome working on liquid/vapor nucleation with Carlo Massimo Casciola. His research activity focuses on mesoscale modelling of fluids, and it is framed in a multidisciplinary context involving fluid mechanics, statistical mechanics, applied mathematics, and high-performance computing. In particular fluctuating hydrodynamics theory and phase field models. Such multiscale models allow coping with a wide spectrum of physical phenomena, such as phase transition in fluids, cellular membrane mechanics, freezing and crystallization dynamics.