Dynamic wetting angle of a spreading droplet

The dynamic contact angle is required as a boundary condition for modelling problems in capillary hydrodynamics, including certain stages of the droplet impact problem. The dynamic contact angle differs appreciably from the static advancing or receding values, even at low velocities. This paper presents experimental results of the dynamic contact angle of spreading droplets after impacting on horizontal and inclined surfaces. Droplets of an 85% (vol.) glycerin/water solution (D = 2.45 mm) and water (D = 2.7 mm) were used in the study. Two surfaces, wax (low wettable) and glass (high wettable) are used, to study the effect of surface wettability (static contact angle). The results include the dynamic contact angle of droplets together with the contact line velocity and the dimensionless spread factor as a function of time.