Numerical simulation of the steady movement of a foam film in a tube

The steady motion of a free foam film rising in a tube is analysed by means of a CFD model. The film consists of a thin central lamella surrounded by a relatively large Plateau border at the wall. The frictional pressure drop generated by the film motion is assumed to be due to viscous shearing arising from the sliding motion of the Plateau border on a thin lubricating liquid-layer falling on the tube wall. The model is based on the solution of the Navier-Stokes and continuity equations in the microscopic Plateau-border region of the foam film. A complex relationship exists between the frictional pressure drop, the thickness of the lubricating film and liquid viscosity. The assumption of a Plateau border with stress-free interfaces leads to pressure drop predictions which are in fair agreement with experimental measurements.