Large amplitude oscillatory shear (LAOS) measurements to obtain constitutive equation model parameters: Giesekus model of banding and nonbanding wormlike micelles

Use policyThe full-text may be used and/or reproduced, and given to third parties in any format or medium, without prior permission or charge, for personal research or study, educational, or not-for-prot purposes provided that:• a full bibliographic reference is made to the original source • a link is made to the metadata record in DRO • the full-text is not changed in any way The full-text must not be sold in any format or medium without the formal permission of the copyright holders.Please consult the full DRO policy for further details. AbstractWe investigate theoretically shear banding in large amplitude oscillatory shear (LAOS) of polymeric and wormlike micellar surfactant fluids. In large amplitude oscillatory shear strain, we observe banding at low frequencies and sufficiently high strain rate amplitudes in fluids for which the underlying stationary constitutive curve of shear stress as a function of shear rate is nonmonotonic. This is the direct (and relatively trivial) analog of quasisteady state banding seen in slow strain rate sweeps along the flow curve. At higher frequencies and sufficiently high strain amplitudes, we report a different but related phenomenon, which we call "elastic" shear banding. This is associated with an overshoot in the elastic (Lissajous-Bowditch) curve of stress as a function of strain and we suggest that it might arise rather widely even in fluids that have a monotonic underlying constitutive curve, and so do not show steady state banding if under a steadily applied shear flow. It is analogous to the elastic banding triggered by stress overshoot in a fast shear startup predicted previously by R. L. Moorcroft and S. M. Fielding [Phys. Rev. Lett. 110(8), 086001 (2013)], but could be more readily observable experimentally in this oscillatory protocol due to its recurrence in each half cycle. In large amplitude oscillatory shear stress, we report shear banding in fluids that shear thin strongly enough to have either a negatively or a weakly positively sloping region in the underlying constitutive curve, noting again that fluids in the latter category do not display steady state banding in a steadily applied flow. This banding is triggered in each half cycle as the stress magnitude transits the region of weak slope in an upward direction such that the fluid effectively yields. It is strongly reminiscent of the transient banding predicted previously in step stress [R. L. Moorcroft and S. M. Fielding, Phys. Rev. Lett. 110(8), 086001 (2013)]. Our numerical calculations are performed in the Rolie-poly model of polymers and wormlike micelles, but we also provide arguments suggesting that our results should apply more widely. Besides banding in the shear strain rate profile, which can be measured by velocimetry, we also predict banding in the shear and normal stress components, measurable by birefringence. As a backdrop to understanding the new results on shear banding in LAOS, we also briefly review earlier work on banding in other time-dependent protocols, focusing in particular on...

Section: A)mentioning

confidence: 96%

Shear banding in large amplitude oscillatory shear (LAOStrain and LAOStress) of polymers and wormlike micelles

Carter¹,

Girkin²,

Fielding³

2016

“…Several works on the rheological characterization of complex fluids deal with large amplitude oscillatory shear (LAOS) in order to generate and to describe the nonlinear behavior of the material (see Hyun et al (2011) for a comprehensive review), as well as a tool to classify complex fluids [Hyun et al (2002)] and obtain constitutive equation model parameters [Gurnon and Wagner (2012)]. Regarding solid viscoelastic suspensions subjected to LAOS regime, a number of experimental works have been carried out, mainly focused on colloidal particles [e.g.…”

Section: Rheology Of Viscoelastic Suspensions Of Spheres Under Small mentioning

confidence: 99%

“…The Giesekus model is chosen as constitutive equation as it has been proven to realistically describe the behavior of non-Newtonian fluids under LAOS [Nam et al (2008); Hyun et al (2011); Gurnon and Wagner (2012)]. To deal with a many-particle system, the sliding-triperiodic domain method is implemented [Hwang et al (2004c)]: the computational domain is periodically replicated along the flow and vorticity directions whereas Lees-Edwards boundary conditions are imposed along the gradient direction.…”

Section: Rheology Of Viscoelastic Suspensions Of Spheres Under Small mentioning

confidence: 99%

Rheology of viscoelastic suspensions of spheres under small and large amplitude oscillatory shear by numerical simulations

D’Avino¹,

Greco²,

Hulsen³

et al. 2013

The dynamic response of a viscoelastic suspension of spheres under small and large amplitude oscillatory shear is investigated by three-dimensional direct numerical simulations. A sliding triperiodic domain is implemented whereby the computational domain is regarded as the bulk of an infinite suspension. A fictitious domain method is used to manage the particle motion. After the stress field is computed, the bulk properties are recovered by an averaging procedure. The numerical method is validated by comparing the computed linear viscoelastic response of Newtonian and non-Newtonian suspensions with previous theories and simulations. The numerical predictions are in very good quantitative agreement with experimental data for the Newtonian case, whereas deviations are found with respect to some sets of experiments for semidilute and concentrated viscoelastic suspensions. To investigate on such discrepancies, the effect of aggregates in the bulk of the suspension is examined. The simulations show that the presence of structures significantly alters the loss modulus. Such an effect is more pronounced as the volume fraction increases. In this light, the above mentioned disagreement between simulations and data (and among experimental data themselves) can be rationalized, as its origin can be attributed to inhomogeneous particle configurations. For increasing strain amplitudes, both loss and storage moduli depart from the linear viscoelastic values. Although the deviations are qualitatively similar to the large amplitude response of the unfilled suspending matrix, our results for dilute and semidilute suspensions show that the decrease of the moduli is more and more pronounced as the volume fraction is higher. Furthermore, a higher concentration of solid particles reduces the value of strain amplitude such that the nonlinear behavior is observed. Simulations at higher frequencies also correctly capture the overshoot in the loss modulus for intermediate strain amplitudes. Finally, the effect of fluid elasticity on the particle motion is analyzed. The particles are found to move away from their starting positions and the average distance, computed at the beginning of each cycle with respect to the initial configuration, linearly increases with the number of cycles. The change in the microstructure is attributed to the long-range hydrodynamic interactions mediated by fluid viscoelasticit

“…Although linear viscoelasticity is useful for understanding the relationship between the microstructure and rheological properties of complex fluids, the linear viscoelastic moduli (G 0 and G 00 ) are limited by the first harmonic Fourier coefficients of G 0 and G 00 , which are insufficient to describe the nonlinear material response with a distorted sinusoidal stress response. The LAOS procedure has been employed to provide more detailed information on the viscoelastic response of materials under nonlinear regimes, by capturing higher harmonic Fourier coefficients or Chebyshev coefficients [Ewoldt (2013); Ewoldt et al (2008)] of stress responses, or fitting experimental data with different viscoelastic models [Blackwell and Ewoldt (2014); Giacomin and Dealy (1998); Gurnon and Wagner (2012); Hyun et al (2002); Rogers and Lettinga (2012)], by applying different flow procedures [Ewoldt (2013); Rogers (2012); Rogers et al (2011)].…”

Section: Large Amplitude Oscillatory Shearmentioning

confidence: 99%

Rheological characterizations of wormlike micellar solutions containing cationic surfactant and anionic hydrotropic salt

Zhao

Haward

Shen

2015

Determination of characteristic lengths and times for wormlike micelle solutions from rheology using a mesoscopic simulation method Journal of Rheology 59, 903 (2015) AbstractAqueous micellar solutions of cationic surfactant cetyltrimethylammonium bromide (CTAB) and organic hydrotropic salt 3-hydroxy naphthalene-2-carboxylate (SHNC) in the semidilute regime have been characterized by linear and nonlinear rheology, and dynamic light scattering. The strong hydrophobicity and naphthalene structure present in the SHNC induces significant growth of CTAB wormlike micelles and promotes stable micellar network formation. Focusing primarily on 75 mM CTAB/SHNC solution, we correlate the rich rheological behavior with structural transitions of the micellar network under different deformation histories with temperatures in the range of 20 C < T < 40 C. Viscous dissipation dominates at low temperature, while short range interactions among micellar head groups, reorganization of micellar networks play important roles at higher temperatures, leading to complex stress responses under large deformations. The influence of double benzene rings on the response of transient and large amplitude oscillatory shear flows in the system was further elucidated by comparing the rheological behavior of CTAB/SHNC with CTAB/NaSal at the same salt and surfactant concentrations. Our studies distinguished SHNC as a stable hydrotrope in a semidilute cationic surfactant system under thermal variations, with potential applications such as drag reduction and fracturing fluids in oil recovery.