Park, S. SDurian, Douglas J2023-05-232023-05-231994-05-232017-10-10https://repository.upenn.edu/handle/20.500.14332/43373We investigate pattern formation in the immiscible displacement of foam from a confining geometry. The dominant length scales with the driving pressure gradient as for a Newtonian fluid, but depends surprisingly on the ratio of plate separation to bubble diameter. The pattern morphology exhibits a transition from a jagged, presumably elastic, character to a smooth, viscous character as the shear strain rate rises far above the natural internal relaxation time scale of the foam. These features may result from the two-dimensional nature of the flows and the unusual rheology of foams.© 1994 American Physical Society. You van view the original article at: https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.72.3347Physical Sciences and MathematicsPhysicsArticle