Polymer Scission and Molecular Weight Prediction in Continuous Abrupt Contraction–Expansion Microchannel with Different Contraction Ratios

Polymer scission is a critical issue in a porous media. This study conducted a two-dimensional model to simulate flow regimes of polymer solutions in channels of varying dimensions, building on a validated numerical methodology and comparing results with experiments. By progressively adjusting the relaxation time and maximum extensibility parameter, the simulation successfully predicted the average molecular weight of polymers after scission in different channels. Analysis of velocity vector field and extensional rates distribution showed that channels with higher contraction ratios exhibited stronger velocity gradients and extensional rates in throats and contraction regions, aligning and stretching polymer chains along the flow and increasing the likelihood of scission. Corner vortices were found to influence both flow behavior and polymer alignment. In contrast, compression dominated in local expansion regions across all channels but had limited impact on polymer alignment, resulting in random orientations and a lower scission risk.