Numerical Simulation for Polymer Blend using OpenFOAM

This thesis models the flow behaviour of polymer blends using a new constitutive model derived from tube theory and double reptation called the bidisperse Rolie-Double-Poly equation (Boudara et al., Journal of Rheology, 63, 71 (2019)) in two different geometrical flows using finite-volume based OpenFOAM software. This model incorporates the molecular mechanisms of reptation motion, thermal and convective constraint release, chain stretch and accounts for the interactions between polymer chain of different lengths in a polydisperse melt. In this thesis, the model was implemented within OpenFOAM using the RheoTool library. This implementation was validated against published results for the transient extensional viscosity. Numerical simulations for the bidisperse Rolie-Double-Poly were performed for two different flow geometries used to characterise extension flow properties, the hyperbolic contraction and a cross-slot with both sharp and hyperbolic corners. For each flow the effects of varying the geometric details, the flow-rate and composition of the blend are examined. In addition, we compare the results to those obtained from the equivalent multimode Rolie-Poly model that is based on linear superposition to distinguish the coupling effect predicts by the Rolie-Double-Poly model. The study of the cross-slot flow is extended to investigate the symmetry-breaking bifurcation for a single mode Rolie-Poly and bidisperse Rolie-Double-Poly model. We find that the bifurcation to a steady asymmetric flow depends on the ratio of the stretch to orientation relaxation times and is not observed when this ratio is small even for high Deborah numbers in the Rolie-Poly model, but is observed in blends described by the Rolie-Double-Poly model.