title: Probing with a laser sheet the contact angle distribution along a contact line.
abstract: An optical method for probing contact angle distribution along contact lines of any shape using a laser sheet is proposed. This method is applied to a dry patch formed inside a film flowing along an inclined plane, both liquid and solid being transparent. Falling normally to the plane, a laser sheet cuts the contact line and is moved along this line. Distortions of the sheet trace observed on a screen put below the plane allow us to extract the contact angle distribution and the local line inclination along the line. Our results show that the contact angle around a dry patch is nearly constant and equal to the static advancing angle, at least when the evolution of its shape is followed for increasing flow rates. This supports a model of dry patch shape recently proposed by Podgorski and co-workers. Preliminary results obtained for decreasing flow are also qualitatively observed.
authors.affiliation: Laboratoire de Physique et Mécanique des Milieux Hétérogènes, UMR 7636 du CNRS, 10 rue Vauquelin, 75 005 Paris, France.
authors.forename: E
authors.initials: E
authors.lastname: Rio
authors.forename: A
authors.initials: A
authors.lastname: Daerr
authors.forename: L
authors.initials: L
authors.lastname: Limat