Upper bound on the stress-induced migration effect in laminar falling film flows of dilute polymer solutions

Abstract

The role of stress-induced migration in falling film flows of dilute polymer solutions is analysed for the limiting case of fully developed concentration field (FDCF). This theoretically derived asymptote is anticipated to serve as an upper bound on the migration effect and our predictions are shown to be consistent with available experimental observations. However, considerable difference between the FDCF asymptote and the experimental data suggests lack of fully developed conditions in most experiments and hence implies the possibility of flow length dependence, a factor hitherto not considered. Finally, a simple approach based on a two-phase model is developed in order to estimate the order of magnitude of film thickness variation that develops along the film length as migration progresses.