Introduction to Drop-Surface Interactions

Abstract

The interaction of drops with surfaces is an everyday occurrence that comprises a rich variety of fluid mechanical facets. Almost two and a half millenniums ago the phrase gutta cavat lapidem (dripping water hollows out a stone) was coined reflecting the erosive action of repetitively impinging drops. The first scientific investigations into certain aspects of drop impact were then conducted in the second half of the nineteenth century. Topics addressed at those times include the formation of vortex rings by drops impinging on liquid surfaces, drops floating on or bouncing off pools, the spreading of a drop of one liquid on the surface of another liquid, splashing and an instability of drops spreading on solid surfaces, the result of the instability being well-known from the formation of ink blots. These and further phenomena of drop-surface interactions will be discussed in the present and in the other chapters of this book. In this we will limit ourselves to the interaction of single drops with different surfaces. It will become clear that processes occurring during drop-surface interactions are governed by a great number of different branches not only of fluid mechanics but also of thermal sciences. Often, a detailed understanding of the processes of drop-surface interactions is not yet available.