Dissipation in foam flowing through narrow channelsI. Cantat1, N. Kern2 and R. Delannay1
1 GMCM UMR 6626, Université Rennes I - 35042 Rennes cedex, France
2 Physics Department, Trinity College Dublin - Dublin 2, Ireland
(Received 31 March 2003; accepted in final form 17 December 2003)
We present measurements on simple foam structures flowing through a narrow channel. Driving pressure and bubble velocity are found to be related by a power law with exponent 2/3, thus extending this relationship from single bubble trains (see Bretherton F. P., J. Fluid Mech. 10 (1961) 166) to more complicated foam structures. This nonlinear behaviour is due to the dominant dissipation mechanism, related to the sliding of Plateau borders over the channel walls. For the first time, we show that the prefactor in the power law strongly depends on the foam structure, through the orientation of the Plateau borders with respect to the flow direction. Our evidence suggests that the normal motion largely dominates the dissipation. We discuss implications for quasi-planar rheological experiments on foams confined between glass plates.
83.50.Ha - Flow in channels.
83.80.Iz - Emulsions and foams.
83.85.Jn - Viscosity measurements.
© EDP Sciences 2004