Spreading of Droplets on Horizontal Surfaces

Abstract

We present experimental results on the impact of single droplets on dry, solid surfaces. The investigation concentrates on the effect of the surface wettability and the effect of the viscosity of the droplet liquid on the spreading process. To characterize the wettability effect, surfaces of glass and wax with different static contact angles are used. To characterize the effect of viscosity the spreading of water and glycerin droplets are compared. To characterize the effect of the surface tension the spreading of isopropanol (liquid with low surface tension) and water droplets are compared. Experiments are performed for different impact velocities. The droplet Weber number varies between 50 and 1080, the Reynolds number varies between 27 and 14800. The results are presented in the form of charts describing the spreading diameter and apex height of droplets in terms of time.