Polymer scission and molecular weight prediction in continuous abrupt contraction–expansion microchannel

This study conducted a two-dimensional numerical simulation of flow in continuous abrupt contraction–expansion microchannel, using experimental measurements as input parameters to validate the reliability of the simulation by comparing the experimental and simulated flow regimes. Memory effects and polymer scission altered flow regime and decrease the elasticity of the solution. Consequently, the relaxation time and maximum extensibility parameter were continuously adjusted in the simulation to match the flow regime in each cavity, successfully predicting the polymer solution's molecular weight after each instance of scission for the first time. The simulation also provided distributions of velocity, extensional rate, and the first normal stress difference, clarifying the mechanism of continuous polymer chain scission during flow. The results suggest that scission likely occurs near the contraction region and the corners between the throat and expansion sections. Along the channel, velocity gradients and extensional rates near the contraction region increase, while first normal stress difference decreases, indicating that chain scission reduces solution elasticity, lowers flow resistance, and increases extensional rates, promoting further chain scission.