title: Response of driven sessile drops with contact-line dissipation.
abstract: A partially-wetting sessile drop is driven by a sinusoidal pressure field that produces capillary waves on the liquid/gas interface. Response diagrams and phase shifts for the droplet, whose contact-line moves with contact-angle that is a smooth function of the contact line speed, are reported. Contact-line dissipation originating from the contact-line speed condition leads to damping for drops with finite contact-line mobility, even for inviscid fluids. The critical mobility and associated driving frequency to generate the largest contact-line dissipation is computed. Viscous dissipation is approximated using the irrotational flow and the critical Ohnesorge number bounding regions beyond which a given mode becomes over-damped is computed. Regions of modal coexistence where two modes can be simultaneously excited by a single forcing frequency are identified. Predictions compare favorably to related experiments on vibrated drops.
authors.affiliation: Department of Mechanical Engineering, Clemson University, Clemson, SC 29631, USA. jbostwi@clemson.edu.
authors.forename: Joshua B
authors.initials: JB
authors.lastname: Bostwick
authors.affiliation: School of Chemical and Biomolecular Engineering and Center for Applied Mathematics, Cornell University, Ithaca, NY 14853, USA.
authors.forename: Paul H
authors.initials: PH
authors.lastname: Steen