A simple geometrical model to predict evaporative behavior of spherical sessile droplets on impermeable surfaces
Publication Name: Contact Angle, Wettability and Adhesion Vol. 4
Publication URL: https://www.taylorfrancis.com/chapters/mono/10.1201/b12166-6/simple-geometrical-model-predict-evaporative-behavior-spherical-sessile-droplets-impermeable-surfaces-kash-mittal?context=ubx&refId=2603cd19-02f6-41ba-a2a2-5c57a6dd5a60
A simple model to predict the evaporative behavior of spherical sessile droplets on impermeable surfaces is presented. The model is capable of predicting changes in shape and volume of spherical droplets resulting from evaporation from the droplet’s caparea. It is demonstrated that at any moment all geometrical parameters of a spherical droplet on a surface (volume, contactangle, contact radius and area, capradius and area, droplet height) can be easily calculated from basic geometrical relations if any two of them are known (e.g.,initial droplet volume and initial contact angle, or droplet capradius and height). Droplet dynamic behavior due to evaporation is further determined using the known value of the evaporation intensity from a unit area of the droplet cap (or evaporation flux). The bulk evaporation rate from the droplet cap decreases proportionally to the shrinking caparea. More complex droplet behavior can be simulated if a receding contact angle value is known. This model was used to simulate experiments performed by the authors as well as reported by the researchers. It is demonstrated that the simple geometrical relations actually account for many features of the sessile droplet dynamic behavior reported in the literature. It is also demonstrated that the often reported bulk evaporation rate, not adjusted for changing droplet cap area, should not be used as a meaningful indicator of droplet dynamics.