Reduction of the effective shear viscosity in polymer solutions due to crossflow migration in microchannels: Effective viscosity models based on DPD simulations

TL Palmer and G Baardsen and R Skartlien, JOURNAL OF DISPERSION SCIENCE AND TECHNOLOGY, 39, 190-206 (2018).

DOI: 10.1080/01932691.2017.1306784

Molecular dynamics simulations (dissipative particle dynamics-DPD) were developed and used to quantify wall-normal migration of polymer chains in microchannel Poseuille flow. Crossflow migration due to viscous interaction with the walls results in lowered polymer concentration near the channel walls. A larger fraction of the total flow volume becomes depleted of polymer when the channel width h decreases into the submicron range, significantly reducing the effective viscosity. The effective viscosity was quantified in terms of channel width and Weissenberg number Wi, for 5% polymer volume fraction in water. Algebraic models for the depletion width delta(Wi, h) and effective viscosity mu(e)(delta/h, Wi) were developed, based on the hydrodynamic theory of Ma and Graham and our simulation results. The depletion width model can be applied to longer polymer chains after a retuning of the polymer persistence length and the corresponding potential/thermal energy ratio. GRAPHICS .

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