ORCID Profile
0000-0002-0785-1508
Current Organisation
Indian Institute of Technology Bombay
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Publisher: AIP Publishing
Date: 06-09-2018
DOI: 10.1063/1.5040397
Abstract: The effect of fluctuating internal viscosity and hydrodynamic interactions on a range of rheological properties of dilute polymer solutions is examined using a finitely extensible dumbbell model for a polymer. Brownian dynamics simulations are used to compute both transient and steady state viscometric functions in shear flow. The results enable a careful differentiation of the influence, on rheological properties, of solvent-mediated friction from that of a dissipative mechanism that is independent of solvent viscosity. In particular, hydrodynamic interactions have a significant influence on the magnitude of the stress jump at the inception of shear flow, and on the transient viscometric functions, but a negligible effect on the steady state viscometric functions at high shear rates. Zero-shear rate viscometric functions of free-draining dumbbells remain essentially independent of the internal viscosity parameter, as predicted by the Gaussian approximation, but the inclusion of hydrodynamic interactions induces a dependence on both the hydrodynamic interaction and the internal viscosity parameter. Large values of the internal viscosity parameter lead to linear viscoelastic predictions that mimic the behavior of rigid dumbbell solutions. On the other hand, steady-shear viscometric functions at high shear rates differ in general from those for rigid dumbbells, depending crucially on the finite extensibility of the dumbbell spring.
Publisher: American Physical Society (APS)
Date: 17-03-2020
Publisher: Society of Rheology
Date: 13-07-2021
DOI: 10.1122/8.0000255
Abstract: A coarse-grained bead-spring-dashpot chain model with the dashpots representing the presence of internal friction is solved exactly numerically for the case of chains with more than two beads. Using a decoupling procedure to remove the explicit coupling of a bead’s velocity with that of its nearest neighbors, the governing set of stochastic differential equations are solved with Brownian dynamics simulations to obtain material functions in oscillatory and steady simple shear flow. Simulation results for the real and imaginary components of the complex viscosity have been compared with the results of previously derived semi-analytical approximations, and the difference in the predictions is seen to diminish with an increase in the number of beads in the chain. The inclusion of internal friction results in a nonmonotonous variation of the viscosity with shear rate, with the occurrence of continuous shear-thickening following an initial shear-thinning regime. The onset of shear-thickening in the first normal stress coefficient is pushed to lower shear rates with an increase in the internal friction parameter.
Publisher: Society of Rheology
Date: 09-11-2022
DOI: 10.1122/8.0000498
Abstract: An exact solution of coarse-grained polymer models with fluctuating internal friction and hydrodynamic interactions has not been proposed so far due to a one-to-all coupling between the connector vector velocities that precludes the formulation of the governing stochastic differential equations. A methodology for the removal of this coupling is presented, and the governing stochastic differential equations, obtained by attaching a kinetic interpretation to the Fokker–Planck equation for the system, are integrated numerically using Brownian dynamics simulations. The proposed computational route eliminates the calculation of the ergence of the diffusion tensor, which appears in models with internal friction, and is about an order of magnitude faster than the recursion-based algorithm for the decoupling of connector-vector velocities previously developed [Kailasham et al., J. Rheol. 65, 903 (2021)] for the solution of freely draining models with internal friction. The effects of the interplay of various combinations of finite extensibility, internal friction, and hydrodynamic interactions on the steady-shear-viscosity are examined. While finite extensibility leads solely to shear-thinning, both internal friction and hydrodynamic interactions result in shear-thinning followed by shear-thickening. The shear-thickening induced by internal friction effects is more pronounced than that due to hydrodynamic interactions.
Publisher: Royal Society of Chemistry (RSC)
Date: 2021
DOI: 10.1039/D1SM00613D
Abstract: The Rouse model with internal friction (RIF) is shown with polymer kinetic theory (PKT) to pre-average internal friction and to neglect fluctuations, significantly affecting the model's prediction of properties at equilibrium and in shear flow.
Location: United States of America
No related grants have been discovered for Rajarshi Chakrabarti.