Titre/Title :
Capillary instabilities of drops and liquid filaments on a substrate
Contact :
Achim Wirth
Résumé/Abstract :
Capillary forces acting on the surface of a fluid are responsible for various instabilities.
I will present two examples for a fluid in contact with a substrate.
First, the time evolution of a liquid filament initially at rest : the growth of capillary waves on its surface and the retraction of the tips both contribute to the dynamics. I will discuss the dependency of the time evolution and of the final configurations on the contact angle formed by the fluid with the substrate.
Second, the surprising dynamics of two drops initially at rest on a super-hydrophobic surface upon coalescence. For a range of fluid densities and viscosities, the merged drop performs an out-of-plane motion due to the conversion of surface energy into kinetic energy.
Results are mostly obtained numerically through a diffuse interface approach. Experiments on Leidenfrost surfaces are also shown for the drop problem.