Showing papers on "Apparent viscosity published in 2013"
TL;DR: The ability to achieve long term stability for nanoparticle stabilized C/W foams could offer an alternative to conventional surfactants, which are known to have much lower adsorption energies.
193 citations
TL;DR: In this paper, the authors reported the rheological and microstructural properties of a kind of novel cold, gel-like soy protein isolate (SPI) emulsions obtained by means of microfluidization.
154 citations
TL;DR: In this article, the viscosity of an active suspension of E. coli bacteria is determined experimentally as a function of the shear rate using a Y-shaped microfluidic channel.
Abstract: The viscosity of an active suspension of E. coli bacteria is determined experimentally as a function of the shear rate using a Y-shaped microfluidic channel. From the relative suspension viscosity, we identify rheological thickening and thinning regimes as well as situations at low shear rate where the viscosity of the bacteria suspension can be lower than the viscosity of the suspending fluid. In addition, bacteria concentration and velocity profiles in the bulk are directly measured in the microchannel.
142 citations
TL;DR: In this article, synergistic interactions at the interface of nanoparticles and surfactant (caprylamidopropyl betaine) led to the generation of viscous and stable CO2-in-water (C/W) foams with fine texture at 19.4 MPa and 50°C.
Abstract: Synergistic interactions at the interface of nanoparticles (bare colloidal silica) and surfactant (caprylamidopropyl betaine) led to the generation of viscous and stable CO2-in-water (C/W) foams with fine texture at 19.4 MPa and 50°C. Interestingly, neither species generated C/W foams alone. The surfactant became cationic in the presence of CO2 and adsorbed on the hydrophilic silica nanoparticle surfaces resulting in an increase in the carbon dioxide/water/nanoparticle contact angle. The surfactant also adsorbed at the CO2–water interface, reducing interfacial tension to allow formation of finer bubbles. The foams were generated in a beadpack and characterized by apparent viscosity measurements both in the beadpack and in a capillary tube viscometer. In addition, the macroscopic foam stability was observed visually. The foam texture and viscosity were tunable by controlling the aqueous phase composition. Foam stability is discussed in terms of lamella drainage, disjoining pressure, interfacial viscosity, and hole formation. © 2013 American Institute of Chemical Engineers AIChE J, 59: 3490–3501, 2013
138 citations
TL;DR: Experimental observations of blood's apparent viscosity in vitro and in vivo are reviewed, and progress towards a quantitative theoretical understanding of the mechanisms involved are progress towards.
109 citations
TL;DR: In this article, the use of a surfactant mixture of natural and synthetic surfactants as additives in stabilizing coal-water slurry (CWS) formed from low rank Indian coals has been explored.
104 citations
TL;DR: In this article, a novel thermoviscosifying polymers (TVPs) whose viscosity increases upon increasing temperature and salinity may overcome the deficiencies of most water-soluble polymers.
Abstract: Polymer flooding represents one of the most efficient processes to enhance oil recovery, but the poor thermostability and salt tolerance of the currently used water-soluble polymers impeded their use in high temperature and salinity oil reservoirs. Thermoviscosifying polymers (TVPs) whose viscosity increases upon increasing temperature and salinity may overcome the deficiencies of most water-soluble polymers. A novel TVP was studied in comparison with traditional partially hydrolyzed polyacrylamide (HPAM) in synthetic brine regarding their rheological behaviors and core flooding experiments under simulated high temperature and salinity oil reservoir conditions (T: 85 °C, and total salinity: 32,868 mg/L, [Ca2+] + [Mg2+]: 873 mg/L). It was found that with increasing temperature, both apparent viscosity and elastic modulus of the TVP polymer solution increase, while those of the HPAM solutions decrease. Such a difference is attributed to their microstructures formed in aqueous solution, which were observed by cryogenic transmission electron microscopy. Core flow tests at equal conditions showed an oil recovery factor of 13.5 % for the TVP solution versus only 2.1 % for the HPAM solution.
81 citations
TL;DR: In this article, the rheological behavior of two commercially available thickening powders and an additional xanthan gum solution with a view to explaining the efficacy of thickened fluids in terms of their rheology was described.
Abstract: The addition of a starch or gum-based thickener to patient fluids with dysphagia is commonly carried out, but the mechanism behind the efficacy of this treatment is not fully understood. This paper describes the rheological behavior of two commercially available thickening powders and an additional xanthan gum solution with a view to explaining the efficacy of thickened fluids in terms of their rheology. Both linear viscoelastic and steady shear data were obtained for the fluids together with filament extensional stretch, decay, and breakup data. In order to follow the behavior of the fluids in a processing situation, a mechanical “Cambridge Throat” was designed and tested. The action of the tongue was modeled using a constant torque cam that forced fluid contained within a flexible membrane through a model throat. Movie photography captured images of the fluid behavior and showed that for a constant tongue torque, the transit time within the model throat increased with increasing fluid viscosity, with implications for the time available for the successful function of the larynx, throat muscles, and epiglottis.
79 citations
TL;DR: The rheological behavior and the mean apparent viscosity of HGA are significantly different from that of water and should therefore be considered important during development of gastric simulated media and in gastric evaluation of lipid-based drug delivery systems.
73 citations
TL;DR: In this paper, a general approach to quantitative description of non-Newtonian flow of polymer melts is achieved if to assume that the dominant reason of nonlinear flow properties is molecular-weight distribution of polydisperse polymers with continuous flow-to-rubbery transition from the side of slow relaxation modes with increasing shear rate.
Abstract: Different possible mechanisms of non-Newtonian behavior of polymeric and multi-component materials in shearing are discussed. There are two main types of the non-Newtonian media: fluids with the maximal (zero-shear-rate) Newtonian viscosity and yielding visco-plastic materials. Numerous intermediate and superimposing situations can also exist. The main concept of the non-Newtonian viscosity of such elastic fluids as polymer melts is based on definition of their “structure” as the set of relaxation modes modified by deformation. Shear-induced relaxation spectrum transformations lead to non-linearity, formation of anisotropic structures, and changes in the macromolecule entanglement topology. A general approach to quantitative description of non-Newtonian flow of polymer melts is achieved if to assume that the dominant reason of non-linear flow properties is molecular-weight distribution of polydisperse polymers with continuous flow-to rubbery transition from the side of slow relaxation modes with increasing shear rate. The non-Newtonian viscosity of such multi-component systems as numerous suspensions, emulsions, and mixtures is characterized by transition from the flow curves with the zero-shear-rate viscosity to the yield-type behavior. The latter is the direct evidence of a spatial structure which changes in shearing. The yield stress value can be rigorously determined only for rigid structures. For soft matters, the structural breakdown/buildup processes are a time dependent (thixotropic/rheopectic) phenomenon, and the concept of yielding becomes uncertain. Nature of structures in various multi-component materials can be very different but just their existence determines a possibility of non-linear effects in shearing. A special type of the non-Newtonian flow is instability and inhomogeneity of a stream. Different forms of these phenomena (shear banding, layered flow, surface distortions, periodic oscillations, concentration separation, and movement of large structural aggregates) are known. In such situations, the “measured” non-Newtonian viscosity can appear an artifact depending on the size factor.
71 citations
TL;DR: In this paper, the influence of xanthan gum (XG) on the properties of the solution containing 3.0% sodium caseinate (CN) was estimated firstly by zeta potential, hydrodynamic diameter (DH) and interfacial tension.
TL;DR: In this article, a discrete model for the apparent viscosity as well as for the maximum packing fraction of polydisperse suspensions of spherical, noncolloidal particles is derived.
Abstract: Based on the notion of a construction process consisting of the stepwise addition of particles to the pure fluid, a discrete model for the apparent viscosity as well as for the maximum packing fraction of polydisperse suspensions of spherical, noncolloidal particles is derived. The model connects the approaches by Bruggeman and Farris and is valid for large size ratios of consecutive particle classes during the construction process, appearing to be the first model consistently describing polydisperse volume fractions and maximum packing fraction within a single approach. In that context, the consistent inclusion of the maximum packing fraction into effective medium models is discussed. Furthermore, new generalized forms of the well-known Quemada and Krieger–Dougherty equations allowing for the choice of a second-order Taylor coefficient for the volume fraction (ϕ2-coefficient), found by asymptotic matching, are proposed. The model for the maximum packing fraction as well as the complete viscosity model is...
TL;DR: It is demonstrated here that irreversible clusters also increase system viscosity in the zero shear limit, and the A/W interface yields, i.e., shows solid-like behavior.
TL;DR: In this article, the rheological characterisation of chestnut flour doughs with chia flour at 4.0g/100g flour basis and a hydrocolloid (guar gum, hydroxypropyl methyl cellulose (HPMC) or tragacanth gum) at different concentrations (0.5, 1.0, 2.0 and 1.b.) was carried out at 30°C using a controlled stress rheometer.
Abstract: The rheological characterisation of chestnut flour doughs with chia flour at 4.0 g/100 g flour basis and a hydrocolloid (guar gum, hydroxypropyl methyl cellulose (HPMC) or tragacanth gum) at different concentrations (0.5, 1.0, 1.5, 2.0 g/100 g, f.b.) was carried out at 30 °C using a controlled stress rheometer. Previously, the mixing behaviour was determined using Mixolab® apparatus. Measurements of shear (0.01–10 s−1), oscillatory (1–100 rad s−1 at 0.1% strain), creep-recovery (loading of 50 Pa for 60 s) and temperature sweep (30–100 °C) were performed. The simultaneous presence of chia and hydrocolloids modified significantly the rheological properties of doughs. Apparent viscosity at constant shear rate and storage and loss moduli at constant angular frequency decreased with increasing hydrocolloid content, except for tragacanth gum which loss modulus exhibited a reverse trend. Creep-recovery data showed that doughs elasticity improved with the presence of guar (65.9%), HPMC (64.8%) or tragacanth (45.8%) at 1.0, 2.0 and 1.0 (g/100 g, f.b.), respectively. Flow curves, mechanical spectra and creep-recovery curves obtained experimentally were satisfactorily fitted using Cross, power and Burgers models, respectively. Gelatinization temperatures decreased with increasing additive content for all systems.
TL;DR: In this article, a set-up composed of a stirred tank reactor and a circulation loop was used to study CO2 hydrate slurry formation and flowing in refrigeration systems.
Abstract: The aim of this paper is to present the rheological properties of CO2 hydrate slurry for a use as secondary fluids in refrigeration systems. A set-up composed of a stirred tank reactor and a circulation loop was used to study CO2 hydrate slurry formation and flowing. Rheological properties of CO2 hydrate slurries circulating in the loop were determined by the capillary viscometer method. The results show a shear thinning behaviour of the CO2 hydrate slurries for a solid fraction up to 22%. This behaviour is correlated by an Ostwald-de-Waele empirical equation, which takes into account the hydrate fraction of the slurry. The apparent viscosity of CO2 hydrate slurry was estimated from the model and a good agreement was found with the experimental data. A comparison with literature shows the importance of using a stirred reactor for slurry homogenisation, which allows the decrease of the apparent viscosity of the slurry.
TL;DR: In this article, the steady and dynamic rheological properties of the dairy dessert samples (puddings) containing carrageenan, alginate, guar and xanthan gums and their combinations were investigated in a model system.
Abstract: In this study, the steady and dynamic rheological properties of the dairy dessert samples (puddings) containing carrageenan, alginate, guar and xanthan gums and their combinations were investigated in a model system, and mixture design was utilized to observe the effects of the gums and their interactions. The flow behaviour of the pudding samples fitted to the Ostwald de Waele model (R
2 > 0.98). All the samples exhibited a gel structure with their higher G′ (storage modulus) values than the G″ (loss modulus) values. Carrageenan was the most effective hydrocolloid on both the steady and dynamic rheological parameters of the dairy dessert samples. On the other hand, alginate had relatively smaller effect. Furthermore, 30 pudding samples containing different gum or gum combinations were classified into two groups (A and B) by using principal component analysis (PCA). Samples containing more than 33% carrageenan in their formulations made up the group A which positively correlated to K (consistency index), η
50 (apparent viscosity at shear rate 50 s−1), G′, G″, G* (complex modulus) and η* (complex viscosity) values.
19 Feb 2013
TL;DR: In terms of the observation times required by a particular method, studies of p-wave attenuation benefit from their short periods (seconds) and all 7 studies cited in Table 2 give upper bound viscosity values within a very confined range of lo*-10' poises as discussed by the authors.
Abstract: Estimates of outer core viscosity span 14 orders of magnitude. This wide range of values may be partially explained by the difference in type of viscosity, molecular viscosity (a rheological property of the material) vis-a-vis a modified or eddy viscosity (a property of the motion), inferred from the various observational and theoretical methods [24]. The motion associated with eddy viscosity implies the possibility of non-viscous dissipative mechanisms such as ohmic dissipation. Molecular viscosity is separated into nearly equal components of shear viscosity, q,, and bulk or volume viscosity, q,, depending on the type of strain involved [ 14,151. 1, is a measure of resistance to isochoric flow in a shear field whereas q” is a measure of resistance to volumetric flow in a 3-dimensional compressional field. In cases where outer core viscosity estimates are based on observations of the attenuation of longitudinal waves, both TJ, and Q play significant roles but only 17, is important for damping whole Earth torsional mode oscillation and 11, for damping radial mode oscillation [4]. The majority of estimates of outer core viscosity is based on whole Earth geodetic and seismological observations. In terms of the observation times required by a particular method, studies of p-wave attenuation benefit from their short periods (seconds) and all 7 studies cited in Table 2 give upper bound viscosity values within a very confined range of lo*-10’ poises. While long period (minutes to years) geodetic phenomena, such as the radial and torsional modes of free oscillation, length of day
TL;DR: In this article, the authors investigated the emulsification properties of polyvinyl alcohols (PVAs) to generate oil-in-water (O/W) emulsions and achieved a signific...
Abstract: Driven by the need to enhance heavy oil production, we have investigated the emulsification properties of poly(vinyl alcohol)s (PVAs) to generate oil-in-water (O/W) emulsions and achieve a signific...
TL;DR: Both optical and scanning electron microscopy (SEM) showed spherical microcapsules with irregular topography due to the presence of holes on its surface, and the obtained size distribution range was modified when the stirring rate was increased.
TL;DR: The authors measured at viscosities ( ) ranging from 10.7 to 104mPa/s via observation along the vorticity of a Poiseuille flow in a glass capillary; decreased steeply with increasing up to a value of 25m Pa/s and remained constant for higher values.
Abstract: Red blood cells are the subject of diverse studies. One branch is the observation and theoretical modelling of their behaviour in a shear flow. This work deals with the flow of single red cells suspended in solutions much more viscous than blood plasma. Below a critical shear rate ( ) the red cells rotate with little change of their resting shape. Above that value they become elongated and aligned in the shear field. We measured at viscosities ( ) ranging from 10.7 to 104 mPa s via observation along the vorticity of a Poiseuille flow in a glass capillary; decreased steeply with increasing up to a value of 25 mPa s and remained constant for higher values. Present theoretical models are not in keeping with the measured data. Modifications of basic model assumptions are suggested.
06 May 2013
TL;DR: In this paper, the stability and dynamic shear properties of grape molasses with varying levels of starch (5, 7.5, and 10%) have been determined at 60 °C, 70 °C and 80 °C.
Abstract: Steady and dynamic shear properties of grape molasses having varying levels of starch (5%, 7.5%, and 10%) have been determined at 60 °C, 70 °C, and 80 °C. The consistency coefficient (K) and apparent viscosity (η50) increased with the starch concentration and decreased with temperature. Similar behavior was also observed in storage modulus (G′), loss modulus (G″), complex modulus (G*), and complex viscosity (η*). The 5-hydroxymethylfurfural (HMF) content of mid-product mix decreased with the increase in the starch concentration. Hardness, gumminess, and chewiness values increased with the starch concentration and temperature. The HMF content of the final product increased with the increase in drying temperature and decreased as the starch concentration increased.
TL;DR: The results clearly demonstrate how appropriate cosurfactants can be used for efficient control of the rheological properties of concentrated surfactant solutions and of some important foam attributes, such as bubble size and foam rheology.
Abstract: Systematic experimental study is performed about the effects of chain length (varied between C8 and C18) and concentration of fatty acids (FAc), used as cosurfactants to the mixture of the anionic surfactant SLES and the zwitterionic surfactant CAPB. The following properties are studied: bulk viscosity of the concentrated solutions (10 wt % surfactants), dynamic and equilibrium surface tensions, surface modulus, and foam rheological properties for the diluted foaming solutions (0.5 wt % surfactants). The obtained results show that C8–C10 FAc induce formation of wormlike micelles in the concentrated surfactant solutions, which leads to transformation of these solutions into viscoelastic fluids with very high apparent viscosity. The same FAc shorten the characteristic adsorption time of the diluted solutions by more than 10 times. In contrast, C14–C18 FAc have small effect on the viscosity of the concentrated solutions but increase the surface modulus above 350 mN/m, which leads to higher friction inside sh...
TL;DR: In this article, the authors analyzed the flow behavior of vegetable-based infant purees at different temperatures (5 −65°C) giving particular attention to their time-dependent properties in a shear rate range.
TL;DR: In this article, a commercially available simulator could accurately simulate single and two-phase polymer coreflood experimental results conducted for a range of injection rates and adherence to physically realistic input values with respect to experimentally derived parameters was of primary importance during the development of the models.
TL;DR: In this paper, an apple puree was ground to obtain dispersions with three different particle size distributions, which induced the separation of parenchyma irregular cell clusters into regular single cells, modifying both the morphology and the particle size distribution.
TL;DR: In this article, a modular β-cyclodextrin copolymer for clay stabilization was prepared from 2-O-(allyloxy-2-hydroxyl-propyl)-β-cyclodesxtrin (XBH), acrylamide (AM), 2-acrylamido-2methyl propane sulfonic acid (AMPS), and sodium acrylate (NaAA) via redox free-radical copolymers.
Abstract: A modular β-cyclodextrin copolymer for clay stabilization was prepared from 2-O-(allyloxy-2-hydroxyl-propyl)-β-cyclodextrin (XBH), acrylamide (AM), 2-acrylamido-2-methyl propane sulfonic acid (AMPS), and sodium acrylate (NaAA) via redox free-radical copolymerization. The effects of reactive conditions (such as initiator concentration, monomer ratio, reaction temperature, and pH) on the apparent viscosity of the copolymer were investigated and the optimal conditions for the copolymerization were established. The copolymer obtained was characterized by infrared spectroscopy, scanning electron microscope, viscosity measurements, rheological measurement, core stress test, and X-ray diffractometry. The crystalline interspace of MMT could be reduced from 18.95323 A to 15.21484 A by copolymer AM/NaAA/AMPS/XBH. And this water-soluble copolymer also showed remarkable anti-shear ability, temperature resistance, and salt tolerance (1000 s−1, viscosity retention rate: 35%; 120°C, viscosity retention rate: 75%; 10,000 mg/L NaCl, viscosity retention rate: 50.2%; 2000 mg/L CaCl2, viscosity retention rate: 48.5%; 2000 mg/L MgCl2, viscosity retention rate: 42.9%). © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013
TL;DR: In this article, a rotational viscometer was used to characterize the flow behavior of date syrup solution at four different temperatures (20, 40, 60, and 80°C) and four concentrations (17, 24, 31 and 39°Brix).
TL;DR: The large amplitude oscillatory shear (LAOS) test and Fourier transform rheology analysis showed that the addition of flaxseed gum strongly affected the structure of the SPI-FG mixed dispersion system as shown by deformation of the nonlinear stress response curve and significantly altered magnitude of higher harmonic curve.