Co-authors: Arnaut Saint-Jalmes, Isabelle Cantat, Mathieu Roché
Location: Institut de Physique de Rennes, Université Rennes 1, Rennes, France – Laboratoire Matière et Systèmes Complexes, Université Paris Diderot, Paris, France – Laboratoire Gulliver, ESPCI-Paris, Paris, France.
A concentrated solution of soluble surfactant is deposited on the surface of water bath, which creates a circular Marangoni flow. This flow extends on a finite length which corresponds to the time needed for the surfactant to diffuse toward the volume. The flow is made visible on the Figure above by adding oil droplets to the surfactant solution: the black circle corresponds to the area where the surface is accelerated, and hence the droplets are diluted on the surface, which lets the dark background visible. Beyond this finite radius of the Marangoni spreading, surface vertices are visible. The object of ths work is to understand the origin of these vertices which shows a well defined characteristic wavelegth and frequency.