Topic
Rheometer
About: Rheometer is a research topic. Over the lifetime, 5759 publications have been published within this topic receiving 125849 citations.
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TL;DR: In this paper, the additive-introduced viscoelastic stress is used to dampen the turbulent vortical structures, decrease the turbulent shear stress, and then decrease the frictional drag.
114 citations
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TL;DR: In this paper, a series of worm-like micelle solutions of both cetylpyridinium chloride and sodium salicylate (NaSal) in an aqueous sodium chloride solution and Cetyltrimethylammonium bromide and NaSal in de-ionized water were used to measure the extensional viscoelasticity of the worms.
Abstract: A filament stretching extensional rheometer and capillary breakup extensional rheometer are used to measure the extensional rheology of a series of wormlike micelle solutions experiencing a uniaxial elongational flow. The experiments are performed using a series of wormlike micelle solutions of both cetylpyridinium chloride and sodium salicylate (NaSal) in an aqueous sodium chloride solution and cetyltrimethylammonium bromide and NaSal in de-ionized water. The linear viscoelasticity of all the wormlike micelle solutions is well described by a Maxwell model with just one or two relaxation times while the steady shear measurements all demonstrate characteristics of shear banding at large shear rates. In transient homogeneous uniaxial extension imposed by a filament stretching rheometer, each of the wormlike micelle solutions demonstrate significant strain hardening. At large extension rates, the wormlike micelle solution filaments are all found to fail through a dramatic rupture near the axial midplane at a constant stress independent of imposed extension rate. The result is an extensional viscosity that decays linearly with increasing extension rate. This filament failure likely stems from the local scission of individual wormlike micelle chains. For the more concentrated solutions, as the imposed extension rate is reduced, a critical extension rate is found below which the filament does not rupture, but instead elastocapillary pinch off is recovered and the elastic tensile stresses achieved in the fluid filament grow far beyond the value observed at rupture. This dramatic upturn in the elastic tensile stress and the extensional viscosity at low extension rates is not intuitively expected and is most likely a result of structural changes to the entangled wormlike micelle solution. Strain hardening is also observed in capillary breakup rheometry experiments, however, when the results of filament stretching and capillary breakup rheometry measurements at nominally the same extension rate are superimposed, the results do not agree; the extensional viscosity measurements from filament stretching are in some instances more than an order of magnitude larger. This result calls into question the use of capillary breakup rheometry for quantitatively measuring the extensional viscosity of wormlike micelle solutions.
114 citations
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TL;DR: In this paper, the authors studied the rheology of cornstarch suspensions, a non-Brownian particle system that exhibits discontinuous shear thickening, and found that the shear region of a nonflowing region seems to prevent or delay shear thinning.
Abstract: We study the rheology of cornstarch suspensions, a non-Brownian particle system that exhibits discontinuous shear thickening. Using magnetic resonance imaging (MRI), the local properties of the flow are obtained by the determination of local velocity profiles and concentrations in a Couette cell. For low rotational rates, we observe shear localization characteristic of yield stress fluids. When the overall shear rate is increased, the width of the sheared region increases. The discontinuous shear thickening is found to set in at the end of this shear localization regime when all of the fluid is sheared: the existence of a nonflowing region, thus, seems to prevent or delay shear thickening. Macroscopic observations using different measurement geometries show that the smaller the gap of the shear cell, the lower the shear rate at which shear thickening sets in. We, thus, propose that the discontinuous shear thickening of cornstarch suspensions is a consequence of dilatancy: the system under flow attempts to...
114 citations
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TL;DR: In this paper, the rheological properties of two types of commercial peanut butter have been studied and a mean volume particle diameter of 6.6μm has been determined, the particle diameter distribution was found to be narrow, and the solids volume fraction was estimated to be 0.6.
Abstract: The rheological properties of two types of commercial peanut butter have been studied. Both products are concentrated suspensions, and differ by the presence of additives. The first type, referred to as “100% peanuts,” is an unstabilized suspension consisting of solid peanut particles in peanut oil which is a Newtonian fluid. The second type, referred to as “smooth,” consists of the same suspension stabilized with a vegetable oil and contains other ingredients such as salt and sugar in very small quantities. A mean volume particle diameter of 6.6 μm has been determined, the particle diameter distribution was found to be narrow, and the solids volume fraction was estimated to be 0.6. Slip encountered in rheometry was greatly reduced by gluing sandpaper to the parallel plates of the rheometer. Both samples behaved like plastic materials and apparent yield stresses of 24 Pa and 370 Pa have been determined for the unstabilized and the stabilized suspensions, respectively. No linear domain was found for both suspensions and the non-linearity was confirmed by deformed Lissajous curves and higher odd harmonics in the output signal of small amplitude oscillatory shear experiments. The stabilized suspension behaved more like a solid, the elastic modulus being larger than the loss modulus and almost independent of the frequency. This solid-like behavior is supposedly caused by strong repulsive (steric) forces induced by the stabilizing agent.
113 citations
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TL;DR: Novel polarizable graphene oxide particles with oxidized groups on their edge and basal planes were prepared by a modified Hummers method, and their electro-responsive electrorheological (ER) characteristics when dispersed in silicone oil were examined with and without an electric field applied.
Abstract: Novel polarizable graphene oxide (GO) particles with oxidized groups on their edge and basal planes were prepared by a modified Hummers method, and their electro-responsive electrorheological (ER) characteristics when dispersed in silicone oil were examined with and without an electric field applied. The fibrillation phenomenon of this GO-based electro-responsive fluid was also observed via an optical microscope under an applied electric field. Both flow curves and dielectric spectra of the ER fluid were measured using a rotational rheometer and a LCR meter, respectively. Its viscoelastic properties of both storage and loss moduli were also examined using a vertical oscillation rheometer equipped with a high voltage generator, finding that the GO-based smart ER system behaves as a viscoelastic material under an applied electric field.
112 citations