The aim of this research is to develop an algorithm to simulate droplets nucleation and growth during dropwise condensation in order to study the droplets spatial distribution. The proposed algorithm starts with droplets distributed based on the Poisson point process and investigates the spatial distribution of droplets using Ripley's L function method. Also, the effects of substrate temperature (T w) and initial density (N D) on the percentage of area occupied by droplets (φ) are studied. Good agreement between model predictions and experimental data for the rate of growth and changes in droplets density (N t) as well as spatial distribution of droplets verifies the validity of the simulating model.
Controlling condensation conditions by surface topography is of prime interest. The aim of this work is to investigate the behavior of water droplets condensing on oriented sub-micrometric structures representing ripples with wavelengths around 800 nm. Droplet behavior was studied on different ripples heights and on untextured surfaces. It was specifically looked at how the presence of ripples creates geometrical confinement, and how that influences the deformation and the orientation of single droplets. Results show that the condensed droplets follow the orientation of textured features, especially with high structures height (150 nm). This is shown by the decreasing of droplet roundness with ripples height. The relative number of circular droplets (roundness near to 1) is around 0.6 for 70 nm high ripples and decrease to around 0.2 for 150 nm high ripples. The corresponding relative number on untextured surface is around 0.5. A mechanism, based on droplets pinning and hysteresis, is proposed to explain the influence of the ripples orientation in a vertical plane, onto the droplet deformation during coalescence step. Finally, the presence of ripples is shown to barely impact breath figure dynamics. Number of droplets and mean droplet radius for the textured and untextured surfaces present a comparable evolution.
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