The motion of a foam lamella traversing an idealised bi-conical pore with a rounded central region

The non-smooth motion of a single foam lamella traversing an idealised rock pore can lead to a significant pressure drop. We vary two parameters defining the shape of a biconical pore in two dimensions, and use Surface Evolver simulations and geometric arguments to demarcate the four different types of possible motion. We predict the transitions between different-shaped pores in which the lamella makes a symmetric or an asymmetric jump, an asymmetric crawl, or undergoes smooth motion. We give the time-averaged pressure drop as a function of pore shape.