Study of Droplet Impact on a Wall using a Sharp Interface Method and Different Contact Line Models

Abstract

In this research, droplet impact on a surface is simulated by using a sharp method for interface modeling. The level-set method along with the ghost fluid method is used to model interface in a sharp fashion. Different contact line models are compared and evaluated at both low and high impact velocities. On a hydrophobic surface, dynamic models developed by Hoffman and Jiang represent a more accurate prediction of droplet behavior during the impact process than the static and molecular kinetic dynamic models, especially at rebounding stage. At lower impact velocities, the Hoffman’s model represents better predictions. However, at higher impact velocities, the Jiang’s model is somewhat more accurate. The molecular dynamic model is not appropriate for high impact velocities. On a hydrophilic surface, at low impact velocities, the Jiang’s model represents satisfactory results, whereas the static and the Hoffman’s models cannot produce accurate results, after initial stages of the impact process. At high impact velocities, the static model shows considerable deviation from the experimental results. The effect of the contact angle on the dynamic behavior of the droplet is investigated. At contact angles lower than 900, the droplet only spreads on the surface after impact. However, at contact angles higher than 900, the droplet starts to recoil after spreading. In this case, it is possible that droplet rebounds from surface after recoiling. Maximum spreading radius of the droplet decreases by an increase in contact angle. At higher contact angles, less time is needed for the droplet to rebound from surface.

Keywords

• Droplet impact; Dynamic contact angle; Level-set method; Ghost fluid method.