Recent advances in our understanding of 'complex fluids' have led to the development of chemical additives that greatly improve spray applications. In this seminar the effects of additives on drop impact phenomena are reviewed, with special attention to the effects of flexible polymer additives. The results can be interpreted in terms of a coil-stretch transition of polymer molecules driven by the hydrodynamic action of the surrounding fluid: at rest, polymer molecules are coiled in a minimum energy conformation, whereas if the hydrodynamic forces are sufficiently large they unfold, opposing an increasing resistance to deformation as they are stretched.
This is a weekly series of informal talks given primarily by members of the soft condensed matter and statistical mechanics groups, but is also open to members of other groups and external visitors. The aim of the series is to promote discussion and learning of various topics at a level suitable to the broad background of the group. Everyone is welcome to attend..