Dissipative particle dynamics simulation of depletion layer and polymer migration in micro- and nanochannels for dilute polymer solutions

Fedosov, Dmitry A.; Em Karniadakis, George; Caswell, Bruce

doi:doi:10.1063/1.2897761

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Multiparticle collision dynamics modeling of viscoelastic fluids

In order to investigate the rheological properties of viscoelastic fluids by mesoscopic hydrodynamics methods, we develop a multiparticle collision (MPC) dynamics model for a fluid of harmonic dumbbells. The algorithm consists of alternating streaming and collision steps. The advantage of the harmonic interactions is that the integration of the equations of motion in the streaming step can be performed analytically. Therefore, the algorithm is computationally as efficient as the original MPC al...

Normal mode partitioning of Langevin dynamics for biomolecules

We propose a novel normal mode multiple time stepping Langevin dynamics integrator called NML. The aim is to approximate the kinetics or thermodynamics of a biomolecule by a reduced model based on a normal mode decomposition of the dynamical space. Our basis set uses the eigenvectors of a mass reweighted Hessian matrix calculated with a biomolecular force field. This particular choice has the advantage of an ordering according to the eigenvalues, which have a physical meaning of being the squar...

The flows of dilute polymer solutions in micro- and nanoscale channels are of both fundamental and practical importance in variety of applications in which the channel gap is of the same order as the size of the suspended particles or macromolecules. In such systems depletion layers are observed near solid-fluid interfaces, even in equilibrium, and the imposition of flow results in further cross-stream migration of the particles. In this work we employ dissipative particle dynamics to study depletion and migration in dilute polymer solutions in channels several times larger than the radius of gyration (R_g) of bead-spring chains. We compare depletion layers for different chain models and levels of chain representation, solvent quality, and relative wall-solvent-polymer interactions. By suitable scaling the simulated depletion layers compare well with the asymptotic lattice theory solution of depletion near a repulsive wall. In Poiseuille flow, polymer migration across the streamlines increases with the Peclet and the Reynolds number until the center-of-mass distribution develops two symmetric off-center peaks which identify the preferred chain positions across the channel. These appear to be governed by the balance of wall-chain repulsive interactions and an off-center driving force of the type known as the Segre–Silberberg effect.

Article Outline

INTRODUCTION
DPD MODEL
1. DPD governing equations
2. Polymer models
  1. FENE spring
  2. Fraenkel spring
3. Wall boundary conditions
HYDROSTATICS OF CONFINED DILUTE POLYMER SOLUTIONS
1. Simulation parameters
2. Simulations with several bead-spring models
3. Effect of the solvent quality
4. Wall-polymer-solvent interactions
5. Influence of the channel width
6. The bead number N effect
POISEUILLE FLOW OF DILUTE POLYMER SOLUTIONS
1. Velocity profiles
2. Polymer migration
SUMMARY

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KEYWORDS and PACS

Keywords

flow simulation, interface phenomena, microchannel flow, Poiseuille flow, polymer solutions

PACS

47.60.Dx

Flows in ducts and channels
68.08.-p

Liquid-solid interfaces
47.11.-j

Computational methods in fluid dynamics

ARTICLE DATA

Digital Object Identifier

http://dx.doi.org/10.1063/1.2897761

PUBLICATION DATA

ISSN

0021-9606 (print)

1089-7690 (online)

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$abstract.society.value is a Member of CrossRef

American Institute of Physics

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