This thesis applies the recently developed dynamic van der Waals theory to perform two-dimensional numerical simulations for two-phase, one-component, non-isothermal, liquid-vapour systems. This model has recently been utilised to produce physically reasonable semi-quantitative results in systems where complicated dynamics restrict alternative methods. Two types of boiling are studied; where problematic features, such as non-uniform temperature and phase transition, are principal characteristics: (i) The effects of substrate wettability in pool boiling: (ii) The applicability of the lubrication approximation to Leidenfrost drops, and the similarities between coalescing non-wetting drops and Leidenfrost drops. Experimental study of these problems is challenging due to the small l...[ Read more ]

This thesis applies the recently developed dynamic van der Waals theory to perform two-dimensional numerical simulations for two-phase, one-component, non-isothermal, liquid-vapour systems. This model has recently been utilised to produce physically reasonable semi-quantitative results in systems where complicated dynamics restrict alternative methods. Two types of boiling are studied; where problematic features, such as non-uniform temperature and phase transition, are principal characteristics: (i) The effects of substrate wettability in pool boiling: (ii) The applicability of the lubrication approximation to Leidenfrost drops, and the similarities between coalescing non-wetting drops and Leidenfrost drops. Experimental study of these problems is challenging due to the small length scales involved, while numerical simulations can resolve the necessary detail.

In pool boiling, bubble growth rate on non-wetting surfaces is seen to be larger than that on wetting surfaces. This is explained by noting that the factors contributing to the rate of bubble growth include not only the strong evaporation at the thermal singularity but also the evaporation from a portion of interface close to the substrate. Based on this, an expression is derived for the contact line speed, showing good agreement with the simulation results. The solutions derived from the lubrication approximation for Leidenfrost drops are found to generally compare well to the simulation results. The robustness of the lubrication approximation is attributed to the common features found in the pressure variation through \he vapour layer, although it breaks down as the evaporative region near the interface is approached. Numerical studies of Leidenfrost drop coalescence find a build-up of vapour in the common space under both drops causing a short-range repulsion. This is achieved through a pressure change that scales in a similar manner to that under a single drop. A threshold drop size exists in order for a horizontal body force to overcome the repulsion.