Polymer degradation behavior in drag-reducing pipe flows based on the Finite Extensible Nonlinear Elastic-Peterlin model

High-molecular polymers can greatly reduce the turbulent hydraulic resistance in fluid pipe transport. However, during the drag-reducing process, polymers undergo mechanical degradation under strong shear stress in turbulent flow. To reveal the interaction mechanisms between polymer degradation and fluid behavior in turbulent flows, we investigated drag-reducing agents (DRA) degradation behaviors in macroscopic flow-through pipe experiments. Polymer concentration and molecular weight effects have been analyzed, and the experimental results showed that the higher the concentration and molecular weight, the better the shear resistance of the polymers in turbulence. Based on the revised Finite Extensible Nonlinear Elastic-Peterlin (FENE-P) model by degraded polymer solution rheological parameters, the drag reduction process of both undegraded and degraded viscoelastic polymer solutions has been simulated. Mean velocity profile, turbulent intensity, turbulent kinetic energy, and turbulent dissipation rate have been obtained, which reveal the polymer degradation behavior in drag-reducing pipe flows. A mechanism of drag reduction failure caused by changes in molecular coil conformation and chain breakage has been proposed, which can be used to explain and predict the polymer degradation process.