Droplet Impact on Solid Surfaces

1. Droplet Impact on Solid Surfaces Investigator: C. M. Megaridis, Mechanical and Industrial Engineering Prime Grant Support: Motorola, NASA • Droplet impact ubiquitous in nature and relevant to many practical technologies (coatings, adhesives, etc.) • Spreading/recoiling of droplets impacting on solid surfaces (ranging from wettable to non-wettable) features rich inertial, viscous and capillary phenomena • Objective is to provide insight into the dynamic behavior of the apparent contact angle  and its dependence on contact-line velocity VCL at various degrees of surface wetting • Perform high-speed imaging of droplet impacts under a variety of conditions • By correlating the temporal behaviors of contact angle  and contact-line speed VCL, the  vs. VCL relationship is established • Common wetting theories are implemented to extract values of microscopic wetting parameters (such as slip length) required to match the experimental data • Surface wettability has a critical influence on dynamic contact angle behavior • There is no universal expression to relate contact angle with contact-line speed • Spreading on non-wettable surfaces indicates that only partial liquid/solid contact is maintained • The present results offer guidance for numerical or analytical studies, which require the implementation of boundary conditions at the moving contact line