We consider a multiphase system in which a liquid drop is suspended in a distinct fluid. Surface-active molecules adsorb to the interface and are often use to stabilize the drop and to reduce surface tension. We also consider liposomes which are self-enclosed structures composed of curved lipid bilayer membranes located at the interface between an internal liquid and a suspending liquid. Lipid bilayer membranes are predominantly made from amphiphilic molecules, a special class of surface-active molecules.

When the suspending liquid is set in motion, viscous stresses dynamically alter the tension distribution at the interface. Our study focuses on understanding the role that interfacial dynamics play on the transfer of energy between the interface and the bulk fluids. We simulate the deformation of a particle in an axisymmetric extensional flow and subsequent relaxation using the boundary integral method.

We model the interface of a surfactant laden drop using the Frumkin surface equation of state and consider equilibrium surfactant concentrations ranging from zero to a highly packed monolayer. The lipid bilayer membrane is modeled using an elastic two-dimensional continuous isotropic material with a varying elastic material property that depends on local area changes. The elastic model was derived considering the mechanical behavior of a highly concentrated surfactant monolayer. We analyze flow field properties such as streamlines, stress field and energy dissipation and identify characteristic flow patterns as a function of interfacial properties.