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

ABSTRACT

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 δ(Wi, h) and effective viscosity μ_e(δ/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.

GRAPHICAL ABSTRACT

KEYWORDS:

• DPD
• effective viscosity
• polymer migration
• polymer rheology
• porous media

Acknowledgments

T. L. Palmer thanks Aksel Hiorth and the University of Stavanger for hosting her project, and Institute for Energy Technology (IFE) for computational facilities. A. Stavland, E. Jettestuen, J. L. Vinningland, and A. Hiorth provided support and comments to our work. G. Baardsen thanks Ø. Jensen and E. Sollum for helpful discussions. The prototype code was developed by R. Skartlien in the earlier CRI FACE, partially supported by RCN. We used the freewares VisIt, TeXstudio, and makebst.

Additional information

Funding

T. L. Palmer was funded by the IOR center via the Research Council of Norway (RCN), ConocoPhillips Skandinavia AS, DONG Energy AS Denmark, Eni Norge AS, ENGIE, Lundin Norway AS, Maersk Oil Norway AS, Statoil Petroleum AS, Wintershall Norge, Schlumberger Norge AS, and Halliburton. G. Baardsen was funded by IFE for developing the parallel version of the code. R. Skartlien was funded by the IOR center and IFE.