Rheo-PIV of a shear-banding wormlike micellar solution under large amplitude oscillatory shear

Dimitriou, Christopher J.; Casanellas, Laura; Ober, Thomas J.; McKinley, Gareth H.

doi:10.1007/s00397-012-0619-9

Cited by 56 publications

(45 citation statements)

References 55 publications

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“…9) the stress smoothly and rapidly approaches its equilibrium value with a relaxation time interval that is shorter than 10 s (corresponding to about 7λ), in the same way as observed in Fig. 8(a) by Britton and Callaghan [5,25] in a cone-plate geometry under steady shear, and also with our previous work on LAOS [45]. However, the time varying velocity profiles reported in this previous studies exhibited a smoother (less sharply banded) shape than the steady shearing profiles presented here.…”

Section: Stress Relaxation and Elastic Instability Onsetsupporting

confidence: 84%

“…The corresponding velocity profiles for this range of applied shear rates are always shear-banded, and composed of an odd number of shear bands. The three-banded velocity profiles are well reproduced by the functional form proposed in Dimitriou et al [45]:…”

Section: Multiple-shear-banded Velocity Profilessupporting

confidence: 59%

“…This allowed for simultaneous time-resolved rheometric and velocimetric data of the sample as it is sheared. This is the same configuration that Dimitriou et al [55] used for the study of waxy crude-oil systems and that we used in our previous work [45] in which we characterized the formation of shear bands under Large Amplitude Oscillatory Shear (LAOS). A detailed description of the apparatus was provided in these two previous references.…”

Section: Rheo-piv Experimental Setupmentioning

confidence: 99%

“…In Dimitriou et al [45] we showed using Particle Image Velocimetry (PIV) that a CPyCl/NaSal solution at [100:60] mM sheared in a cone-plate geometry could exhibit shear-band formation under oscillatory shear flows when the applied deformation rate and amplitude exceeded a shearing threshold, typically W i = λω/θ 0 > 1, where the relaxation time of the fluid is λ = 1.45 s, θ 0 is the cone angle, and ω the angular velocity. The velocity profiles displayed three bands, agreeing with the results of Britton and…”

Section: Introductionmentioning

confidence: 99%

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Spatiotemporal dynamics of multiple shear-banding events for viscoelastic micellar fluids in cone-plate shearing flows

Casanellas¹,

Dimitriou²,

Ober³

et al. 2015

Journal of Non-Newtonian Fluid Mechanics

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We characterize the transient response of semi-dilute wormlike micellar solutions under an imposed steady shear flow in a cone-plate geometry. By combining conventional rheometry with 2-D Particle Image Velocimetry (PIV), we can simultaneously couple the temporal stress response with time-resolved velocimetric measurements. By imposing a well defined shear history protocol, consisting of a stepped shear flow sweep, we explore both the linear and nonlinear responses of two surfactant solutions: cetylpiridinium chloride (CPyCl) and sodium salicylate (NaSal) mixtures at concentrations of [66:40] mM and [100:60] mM, respectively. The transient stress signal of the more dilute solution relaxes to its equilibrium value very fast and the corresponding velocity profiles remain linear, even in the strongly shear-thinning regime. The more concentrated solution also exhibits linear velocity profiles at small shear rates. At large enough shear rates, typically larger than the inverse of the relaxation time of the fluid, the flow field reorganizes giving rise to strongly shear-banded velocity profiles. These are composed of an odd number of shear bands with lowshear-rate bands adjacent to both gap boundaries. In the non-linear regime long transients (much longer than the relaxation time of the fluid) are observed in the transient stress response before the fluid reaches a final, fully-developed state. The temporal evolution in the shear stress can be correlated with the spatiotemporal dynamics of the multiple shear-banded structure measured using RheoPIV. In particular our experiments show the onset of elastic instabilities in the flow which are characterized by the presence of multiple shear bands that evolve and rearrange in time resulting in a slow increase in the average torque acting on the rotating fixture.

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Section: Stress Relaxation and Elastic Instability Onsetsupporting

confidence: 84%

Section: Multiple-shear-banded Velocity Profilessupporting

confidence: 59%

Section: Rheo-piv Experimental Setupmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Spatiotemporal dynamics of multiple shear-banding events for viscoelastic micellar fluids in cone-plate shearing flows

Casanellas¹,

Dimitriou²,

Ober³

et al. 2015

Journal of Non-Newtonian Fluid Mechanics

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“…Shear banding is a phenomena in the flow induced by instabilities in the grease phases (base oil and thickener), causing the shear rate in the flow to vary across the channel width [10,16]. One important application where the occurrence of shear banding have a direct impact on the results is in rheometers.…”

Section: Shear Bandingmentioning

confidence: 99%

Grease flow in an elbow channel

Westerberg

Farré-Lladós

et al. 2015

Tribol Lett

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Lubricating greases are materials characterized by a complex nonNewtonian rheology. This study is a continuation of previous studies on the coupling between grease rheology and grease flow in a straight channel-and concentric cylinder geometry. The problem has been modeled and validated with experiments. Here the flow in an elbow channel introducing a non-symmetric distribution of shear stress throughout the cross section of the channel elbow, as well as varying shear rates through the transition from the channel inlet to the outlet. The flow has been modeled both for higher flow rates and for creep flow. The influence of the grease rheology and flow conditions to wall slip, shear banding and an observed stick-slip type of motion observed for low flow rates are presented. The effect on the flow of the applied pressure is also investigated showing that the flow is sensitive to the pressure in the angular (ϕ) direction of the elbow. For high flow rates it is shown that flow separation occur with a resulting circulation in the elbow.

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Rheological Measurements

2013

Encyclopedia of Polymer Science and Technology

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Rheology is the science to study the flow and deformation of matter. It becomes an important field in material science and engineering, food, biotechnology, and so on. The objects in rheological study are not the ideal solid and ideal fluid, which can be described by the Hookean elastic model and the Newtonian viscous model, respectively. Instead, the rheological study often focuses on materials that can exhibit viscous, elastic, and plastic behavior under different flow conditions. They are often termed as complex fluids or soft matter, which include polymers, gels, suspensions, emulsions, biofluids, foods, inks (1). In contrast to hydrodynamics, which often accounts for the complex flow behavior of simple fluids, simple geometry is utilized in rheological measurements to understand the rather complicated relationship between the mechanical input and output of complex fluids. The real flow fields encountered in many applications (such as polymer extrusion, injection molding, blow molding, fiber spinning, inkjet printing, coating) are rather complicated (2). It becomes a problem whether the rheological measurements that performed under simple flow fields are useful in understanding the complicated flow behaviors of complex fluids. Fortunately, it has been proved in many examples that the properties determined from simple rheological measurements are sufficient to quantify the material parameters in various constitutive equations, which have been used widely and successfully to simulate the flow behaviors in polymer processing (3-11). The most frequently used simple flow fields are simple shear flow and simple extensional flow.The simplest geometry that defines the simple shear is two infinite parallel plates separated by a distance h. The liquid is set between two plates with one plate moving parallel to the other (Fig. 1). In reality, when the length L and the width B are much larger than the gap h, the flow in the center regime resembles the flow between two infinite plates. It means that the edge effects are ignored in most experimental shear geometries. In rheological measurements, the flow between two plates should be laminar. Moreover, it is usually assumed that the velocity across the gap satisfies a linear profile. As shown in Fig. 1, if the bottom plate is fixed and the upper plate moves horizontally with the velocity V, the fluid velocity varies linearly from 0 at the bottom plate to V at the upper plate if the no-slip boundary condition is satisfied. The linear velocity profile generates a constant velocity gradient, which is known as the shear rate. Then, the flow field between two parallel plates is homogeneous in the shear rate. The homogeneous assumption is nontrivial in the rheological tests since the actual velocity

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Rheo-PIV of a shear-banding wormlike micellar solution under large amplitude oscillatory shear

Cited by 56 publications

References 55 publications

Spatiotemporal dynamics of multiple shear-banding events for viscoelastic micellar fluids in cone-plate shearing flows

Spatiotemporal dynamics of multiple shear-banding events for viscoelastic micellar fluids in cone-plate shearing flows

Grease flow in an elbow channel

Rheological Measurements

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