Dissipative particle dynamics simulation of dilute polymer solutions—Inertial effects and hydrodynamic interactions

Abstract

We examine the accuracy of dissipative particle dynamics (DPD) simulations of polymers in dilute solutions with hydrodynamic interaction (HI), at the theta point, modeled by setting the DPD conservative interaction between beads to zero. We compare the first normal-mode relaxation time extracted from the DPD simulations with theoretical predictions from a normal-mode analysis for theta chains. We characterize the influence of bead inertia within the coil by a ratio Lm/Rg, where Lm is the ballistic distance over which bead inertia is lost, and Rg is the radius of gyration of the polymer coil, while the HI strength per bead h* is determined by the ratio of bead hydrodynamic radius (rH) to the equilibrium spring length. We show how to adjust h* through the spring length and monomer mass, and how to optimize the accuracy of DPD for fixed h* by increasing the friction coefficient (γ ≥ 9) and by incorporating a nonlinear distance dependence into the frictional interaction. Even with this optimization, DPD simulations exhibit deviations of over 20% from the theoretical normal-mode predictions for high HI strength with h* ≥ 0.20, for chains with as many as 100 beads, which is a larger deviation than is found for Stochastic rotation dynamics simulations for similar chains lengths and values of h*.

Viscosity measurement techniques in Dissipative Particle Dynamics

“…(2) for conservative force will increase the second term as well (virial part). Increase in shear viscosity by increasing the maximum repulsion parameter has been also observed in the literature [19]. These two effects together will increase the viscosity of a DPD system as a function of temperature, which is in contradiction with the standard temperature dependence of the shear viscosity.…”

“…Polymer melts and solutions, as well as multiphase systems have also been studied with special emphasis on their rheological behavior using DPD [9,16,17]. However, one can conclude from a careful review of the prior publications that, even for the simplest system (water, first studied by Groot and Warren [2]), values reported for the viscosity vary from one report to another, depending on the type of flow and method used for calculation of viscosity, boundary conditions and the choice of force parameters [17][18][19][20]. In particular, different viscosity values from Green-Kubo [21] expression for stress autocorrelation function (zero-shear viscosity), stress tensor for steady shear simulations, Poiseuille flow and transient startup shear flow have been reported.…”

Microstructural Rearrangements and their Rheological Implications in a Model Thixotropic Elastoviscoplastic Fluid

“…To span this wide range of length or time scales, we perform dissipative particle dynamics (DPD) [23] simulations on model TEVP fluids consisting of 10 vol % attractive hexagonal solid particles designed to represent the waxy crystalline particles observed in a waxy crude oil [3,24]. The DPD formalism inherently preserves multibody hydrodynamics by conservation of mass and momentum both locally and globally [25,26]. Furthermore, by incorporating relevant interaction potentials for PRL 118, 048003 (2017) P H Y S I C A L…”

Effect of solvent quality on Poiseuille flow of polymer solutions in microchannels: A dissipative particle dynamics study

“…It must be pointed out that both the polymer particles and solvent particles are explicitly modeled in the DPD model, and consequently, the DPD model naturally incorporates hydrodynamic interactions between polymer beads. The motion of a DPD particle in a chain causes a point force on the surrounding solvent particles affecting the motion of the adjacent polymer particle, that is, inducing hydrodynamic interactions between polymer particles …”

“…The DPD particles represent clusters of molecules moving off‐lattice, and the interaction between the particles is symmetrical to ensure momentum conservation. Since polymer chains and solvents are explicitly modeled using DPD particles, the DPD model of polymer solution naturally incorporates hydrodynamic interactions and exclude–volume interactions . This makes DPD method reasonable and popular for studying the dynamics of polymer solutions and other polymer systems .…”