In this work, we extend the classical analysis of concentration fluctuations in polymer solutions under shear flow to consider the same phenomenology under mixed (shear + extensional) flows. To investigate… Click to show full abstract
In this work, we extend the classical analysis of concentration fluctuations in polymer solutions under shear flow to consider the same phenomenology under mixed (shear + extensional) flows. To investigate this phenomenon, we couple stress and concentration using a two-fluid model with fluctuations driven by thermal noise incorporated through a canonical Langevin approach. The polymer stress is governed by the Rolie-Poly model augmented with finite extensibility to account for large stretching of chains at high Weissenberg numbers. Perturbing the equations about homogeneous flow for weak amplitude inhomogeneities, but arbitrary flow strength, we solve for the steady state structure factor (Fourier transformed pair correlation function) under general linear flows using a unique method of characteristics solver. Under shear flow, the model predicts butterfly patterns in accord with previous experimental and theoretical work, including a full rotation of peaks past the flow axis. In addition, the magnitude o...
               
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