Modeling and simulating the growth of ellipsoidal droplets during dropwise condensation on pillared surfaces

A numerical simulation model is proposed to describe ellipsoidal droplets growth on pillared substrates during dropwise condensation. Comparison between gray scale images taken from droplets growing on pillared surfaces with those growing on flat surfaces shows considerable differences that must be taken into account in the simulation model. Firstly, since the droplets can be easily canalized between the pillars, the shape of droplets change from spherical to ellipsoidal specially in coalescence step. Secondly, on pillared surfaces due to droplets three dimensional configuration, coalescence can occur in all three dimensions. And thirdly, if a droplet touches a pillar, they will stay in touch until the end of the process. The model proposed here calculates the growth rate of ellipsoidal droplets during adsorption and coalescence steps, and checks the coalescence by verifying the existence of real intersection between each pair of droplets. The results of this model is compared with real data from 6 different configurations of pillars. The mean relative error of the model for droplets density is 10.00 +/- 0.68%, while it proposes more accurate results for predicting droplets radius with the mean error of 2.28 +/- 0.42%.