scholarly journals Active Brownian Filamentous Polymers under Shear Flow

Polymers ◽  
2018 ◽  
Vol 10 (8) ◽  
pp. 837 ◽  
Author(s):  
Aitor Martín-Gómez ◽  
Gerhard Gompper ◽  
Roland Winkler
Keyword(s):  
Shear Rate ◽  
Shear Flow ◽  
Persistence Length ◽  
Relaxation Times ◽  
Shear Thinning ◽  
Weissenberg Number ◽  
Flexible Polymers ◽  
Orientation Relaxation ◽  
Independent Behavior ◽  
Analytical Expressions

The conformational and rheological properties of active filaments/polymers exposed to shear flow are studied analytically. Using the continuous Gaussian semiflexible polymer model extended by the activity, we derive analytical expressions for the dependence of the deformation, orientation, relaxation times, and viscosity on the persistence length, shear rate, and activity. The model yields a Weissenberg-number dependent shear-induced deformation, alignment, and shear thinning behavior, similarly to the passive counterpart. Thereby, the model shows an intimate coupling between activity and shear flow. As a consequence, activity enhances the shear-induced polymer deformation for flexible polymers. For semiflexible polymers/filaments, a nonmonotonic deformation is obtained because of the activity-induced shrinkage at moderate and swelling at large activities. Independent of stiffness, activity-induced swelling facilitates and enhances alignment and shear thinning compared to a passive polymer. In the asymptotic limit of large activities, a polymer length- and stiffness-independent behavior is obtained, with universal shear-rate dependencies for the conformations, dynamics, and rheology.

Analysis of Flow of Shear Thinning Colloidal and Polymeric Systems Which Exhibit Elastic Recovery or Rigidity

1967 ◽  
Vol 40 (5) ◽  
pp. 1505-1515
Author(s):  
T. Gillespie
Keyword(s):  
Experimental Data ◽  
Relaxation Time ◽  
Shear Rate ◽  
Elastic Recovery ◽  
Relaxation Times ◽  
Shear Thinning ◽  
Structural Theory ◽  
Polymeric Systems ◽  
New Equation

Abstract The hydrodynamic-structural theory of viscosity is extended to take into account the possibility of a distribution of relaxation times. A new equation is presented which is easily applied to experimental data. The effect of a distribution of lifetimes is to extend the range of shear rate over which shear thinning occurs. When the ratio of the largest relaxation time to the smallest relaxation time is greater than 1 but less than 10 the new equation gives results in agreement with the Willamson equation. When this ratio of maximum relaxation time to minimum relaxation time is 300 ± 100 the new equation agrees with an equation recently suggested by Cross. The utility of the new equation is discussed and is illustrated by using it to determine the relaxation time spectra in polystyrene melts.

scholarly journals The Chain Distribution Tensor: Linking Nonlinear Rheology and Chain Anisotropy in Transient Polymers

Polymers ◽  
2018 ◽  
Vol 10 (8) ◽  
pp. 848 ◽  
Author(s):  
Shankar Lalitha Sridhar ◽  
Franck Vernerey
Keyword(s):  
Shear Rate ◽  
Polymer Networks ◽  
Shear Thickening ◽  
Shear Thinning ◽  
Underlying Mechanism ◽  
Weissenberg Number ◽  
Critical Shear Rate ◽  
Nonlinear Rheology ◽  
Non Gaussian ◽  
Chain Force

Transient polymer networks are ubiquitous in natural and engineered materials and contain cross-links that can reversibly break and re-form. The dynamic nature of these bonds allows for interesting mechanical behavior, some of which include nonlinear rheological phenomena such as shear thickening and shear thinning. Specifically, physically cross-linked networks with reversible bonds are typically observed to have viscosities that depend nonlinearly on shear rate and can be characterized by three flow regimes. In slow shear, they behave like Newtonian fluids with a constant viscosity. With further increase in shear rate, the viscosity increases nonlinearly to subsequently reach a maximum value at the critical shear rate. At this point, network fracture occurs followed by a reduction in viscosity (shear-thinning) with a further increase in shear rate. The underlying mechanism of shear thickening in this process is still unclear with debates between a conversion of intra-chain to inter-chain cross-linking and nonlinear chain stretch under high tension. In this paper, we provide a new framework to describe the nonlinear rheology of transient polymer networks with the so-called chain distribution tensor using recent advances from the transient network theory. This tensor contains quantitatively and statistical information of the chain alignment and possible anisotropy that affect network behavior and mechanics. We investigate shear thickening as a primary result of non-Gaussian chain behavior and derive a relationship for the nonlinear viscosity in terms of the non-dimensional Weissenberg number. We further address the criterion for network fracture at the critical shear rate by introducing a critical chain force when bond dissociation is suddenly accelerated. Finally, we discuss the role of cross-linker density on viscosity using a “sticky” reptation mechanism in the context of previous studies on metallo-supramolecular networks with reversible cross-linkers.

Rheological Characterization of Polyethylene Oxide (PEO): An Experimental Steady State and Transient Analysis

2020 ◽  
Author(s):  
Hafiz Ahmad ◽  
M'hamed Boutaous ◽  
Shihe Xin ◽  
Hervé Pabiou ◽  
Dennis A. Siginer
Keyword(s):  
Shear Rate ◽  
Shear Flow ◽  
Polyethylene Oxide ◽  
Shear Thinning ◽  
Data Generation ◽  
Rheological Characterization ◽  
Flow Measurements ◽  
Shear Rates ◽  
Lower Shear ◽  
Lower Shear Rate

Abstract In this paper, the rheological characteristics of aqueous PEO (Polyethylene oxide) solution with very high molecular weight 4 × 106 g/mol is investigated. Shear flow measurements were carried out in steady and transient modes. The unique behavior of PEO is found to be heavily dependent on the input shear rate and the mechanism of data generation. Generally, PEO is found to be shear-thinning throughout the experiments, but at the start of the experiments at low shear rates, minimum input shear value also affects the shear-thinning behavior. In this study, we investigate the critical method of applying input shear to the samples in the lower shear rate regime. Surprisingly, different input methods yield different results. Viscosity curves obtained through shear flow experiments are found to be significantly dependent on the input method of shear rate. Experimental measurements were validated by Cross and Carreau-Yasuda models.

On Shear Thinning in Dilute Polymer Solutions

1989 ◽  
Vol 177 ◽  
Author(s):  
Yitzhak Rabin ◽  
H. C. Öttinger ◽  
K. Kawasaki
Keyword(s):  
Shear Rate ◽  
Polymer Solutions ◽  
Shear Thickening ◽  
Shear Thinning ◽  
Weissenberg Number ◽  
Dilute Polymer Solutions

ABSTRACTWhile recent remrmalization group studies predict shear thickening in the limit of large Weissenberg numbers, scaling theories predict shear thinning. The ocntroversy is related to the question whether the Weissenberg number or the shear rate should be kept fixed when taking the limit of infinitely long polymers.

Heat/mass transport in shear flow over a heterogeneous surface with first-order surface-reactive domains

2015 ◽  
Vol 782 ◽  
pp. 260-299 ◽  
Author(s):  
Preyas N. Shah ◽  
Eric S. G. Shaqfeh
Keyword(s):  
Mass Transfer ◽  
Shear Rate ◽  
Shear Flow ◽  
Reaction Rate ◽  
Patch Size ◽  
Patch Area ◽  
First Order ◽  
Effective Boundary ◽  
Order Surface ◽  
Slip Distance

Surfaces that include heterogeneous mass transfer at the microscale are ubiquitous in nature and engineering. Many such media are modelled via an effective surface reaction rate or mass transfer coefficient employing the conventional ansatz of kinetically limited transport at the microscale. However, this assumption is not always valid, particularly when there is strong flow. We are interested in modelling reactive and/or porous surfaces that occur in systems where the effective Damköhler number at the microscale can be $O(1)$ and the local Péclet number may be large. In order to expand the range of the effective mass transfer surface coefficient, we study transport from a uniform bath of species in an unbounded shear flow over a flat surface. This surface has a heterogeneous distribution of first-order surface-reactive circular patches (or pores). To understand the physics at the length scale of the patch size, we first analyse the flux to a single reactive patch. We use both analytic and boundary element simulations for this purpose. The shear flow induces a 3-D concentration wake structure downstream of the patch. When two patches are aligned in the shear direction, the wakes interact to reduce the per patch flux compared with the single-patch case. Having determined the length scale of the interaction between two patches, we study the transport to a periodic and disordered distribution of patches again using analytic and boundary integral techniques. We obtain, up to non-dilute patch area fraction, an effective boundary condition for the transport to the patches that depends on the local mass transfer coefficient (or reaction rate) and shear rate. We demonstrate that this boundary condition replaces the details of the heterogeneous surfaces at a wall-normal effective slip distance also determined for non-dilute patch area fractions. The slip distance again depends on the shear rate, and weakly on the reaction rate, and scales with the patch size. These effective boundary conditions can be used directly in large-scale physics simulations as long as the local shear rate, reaction rate and patch area fraction are known.

Investigation on the Rheological Behavior of Polyamide6/Montmorillonite Nanocomposites by Reactive Extrusion

2011 ◽  
Vol 233-235 ◽  
pp. 1998-2001 ◽  
Author(s):  
Ming Zhao ◽  
Xiao Zhong Lu ◽  
Kai Gu ◽  
Xiao Min Sun ◽  
Chang Qing Ji
Keyword(s):  
Activation Energy ◽  
Shear Stress ◽  
Shear Rate ◽  
Rheological Behavior ◽  
Reactive Extrusion ◽  
Shear Thinning ◽  
Experimental Results ◽  
Montmorillonite Nanocomposites

The rheological behavior of PA6/montmorillonite(MMT) by reactive extrusion was investigated using cone-and-plate rheometer. The experimental results indicated that PA6/MMT exhibited shear-thinning behavior. The shear stress of both neat PA6 and PA6/MMT increased with the increase in the shear rate. The reduction of the viscous activation energy with the increase of shear stress reflected PA6/MMT can be processed over a wider temperature.

Kinetics of flowing dispersions. X. Oscillations in optical properties of streaming suspensions of spheroids

1977 ◽  
Vol 55 (24) ◽  
pp. 4243-4256 ◽  
Author(s):  
A. Okagawa ◽  
S. G. Mason
Keyword(s):  
Light Scattering ◽  
Shear Flow ◽  
General Pattern ◽  
Relaxation Times ◽  
Simple Shear Flow ◽  
Scattering Coefficients ◽  
Human Red Blood Cells ◽  
Dielectric Particles ◽  
Dilute Suspensions ◽  
Orientation Distributions

Transients in angular light scattering and turbidity of dilute suspensions of nearly monodisperse spheroidal particles undergoing simple shear flow have been investigated by combining Rayleigh–Debye light scattering theory for single dielectric particles with fluid mechanical theory for the orientation distributions of particle assemblies in shear flow. Applying shear to an initially isotropic suspension causes the orientation distributions and thus the angular scattering coefficients to oscillate. Various geometrical arrangements are considered with a view to selecting those that will maximize such rheo-optical effects.By calculating the optical scattering cross section of a single particle, the turbidity of a suspension is obtained; like the scattering coefficient, it undergoes oscillations that are damped by (1) the inevitable spread in particle shape and volume in real systems, (2) shear-induced particle interactions, and (3) rotary Brownian motion. The rates of damping, expressed as relaxation times, are considered for the three mechanisms acting alone or in concert.Preliminary measurements of the turbidity of dilute suspensions of hardened human red blood cells confirm this general pattern of behavior. Apart from their intrinsic interest, such rheo-optical effects can be used to determine a number of useful properties of dispersions.

Dynamics of a non-spherical microcapsule with incompressible interface in shear flow

2011 ◽  
Vol 678 ◽  
pp. 221-247 ◽  
Author(s):  
P. M. VLAHOVSKA ◽  
Y.-N. YOUNG ◽  
G. DANKER ◽  
C. MISBAH
Keyword(s):  
Shear Rate ◽  
Shear Flow ◽  
Viscosity Ratio ◽  
Perturbation Expansion ◽  
Shear Plane ◽  
Creeping Flow ◽  
Regular Perturbation ◽  
Cell Dynamics ◽  
Initial Shape ◽  
Flow Equations

We study the motion and deformation of a liquid capsule enclosed by a surface-incompressible membrane as a model of red blood cell dynamics in shear flow. Considering a slightly ellipsoidal initial shape, an analytical solution to the creeping-flow equations is obtained as a regular perturbation expansion in the excess area. The analysis takes into account the membrane fluidity, area-incompressibility and resistance to bending. The theory captures the observed transition from tumbling to swinging as the shear rate increases and clarifies the effect of capsule deformability. Near the transition, intermittent behaviour (swinging periodically interrupted by a tumble) is found only if the capsule deforms in the shear plane and does not undergo stretching or compression along the vorticity direction; the intermittency disappears if deformation along the vorticity direction occurs, i.e. if the capsule ‘breathes’. We report the phase diagram of capsule motions as a function of viscosity ratio, non-sphericity and dimensionless shear rate.

Effects of shear rate on rouleau formation in simple shear flow

Biorheology ◽  
1988 ◽  
Vol 25 (1-2) ◽  
pp. 113-122 ◽  
Author(s):  
T. Murata ◽  
T.W. Secomb
Keyword(s):  
Shear Rate ◽  
Shear Flow ◽  
Simple Shear ◽  
Simple Shear Flow ◽  
Rouleau Formation

scholarly journals Start-up shear flow of a shear-thinning fluid that approximates the response of viscoplastic fluids

2022 ◽  
Vol 412 ◽  
pp. 126571
Author(s):  
Sai Manikiran Garimella ◽  
Mohan Anand ◽  
Kumbakonam R. Rajagopal
Keyword(s):  
Shear Flow ◽  
Shear Thinning ◽  
Viscoplastic Fluids ◽  
Start Up ◽  
Shear Thinning Fluid
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