Impact of Geometry on Film Boiling Interface Dynamics and Heat Transfer

This study aims to explore film boiling on heated horizontal surfaces through direct numerical simulations conducted in both two-dimensional and axisymmetric domains. We investigate how geometric constraints and symmetry influence the growth and evolution of the vapor–liquid interface, bubble dynamics, and heat transfer characteristics. In the 2D case, interfacial disturbances manifest as sinusoidal waves extending infinitely in the out-of-plane direction, allowing straightforward interpretation of growth rates via wavenumber adjustments. In contrast, the axisymmetric configuration, formulated in cylindrical coordinates, features disturbances characterized by Bessel-function modes, which do not directly correspond to simple sinusoidal waves, complicating direct comparison with 2D results. We intend to quantify differences in instability growth rates, bubble shape evolution, detachment timing, and wall heat flux distribution under identical thermophysical conditions. It is anticipated that axisymmetric geometry will promote stronger curvature-driven localization, potentially accelerating film thinning and bubble detachment compared to the 2D case. While linear growth rates of symmetric 3D disturbances with separable wavenumbers may be inferred approximately from 2D simulations by adjusting effective wavenumber magnitude, this simplification does not hold rigorously for axisymmetric modes due to their distinct radial eigenfunctions. Heat transfer rates are expected to reflect these geometric differences through variations in local Nusselt numbers and vapor recoil effects. This computational comparison seeks to deepen understanding of the interplay between dimensionality, interface instability, and thermal transport in film boiling phenomena, shedding light on the limitations of reduced-dimensionality models and motivating future fully three-dimensional investigations.