Predicting sensory perceptions of thickened solutions based on rheological analysis

Segmental blood flow and rheological determinants in diabetic patients with peripheral occlusive arterial disease

Enhancement of flocculant-aided filtration performance of coal tailings under alternating low and high shear rates

Commercially available recycled polypropylene (R-PP) and recycled bottle grade polyethylene terephthalate (R-PET) were melt compounded in different proportions of R-PET in twin screw extruder at temperatures used typically for PP processing. The melt flow behaviour was investigated for these blends using capillary rheometer at different temperatures viz. 230, 250, 260°C. The crystallization and structure development was studied using DSC and XRD. The melt viscosity (η) of these blends followed the usual non-Newtonian behaviour with decrease of η with high shear rate (γ′) and saturation at low shear rate. Most noteworthy finding was that the low shear viscosity at melt temperatures of 230 and 250 showed a peak with increase of R-PET content while at 260°C there was uniform decrease in the viscosity with addition of R-PET. The high shear viscosity also showed similar trend but with less pronounced changes. This was attributed to the cross over of domain shape from spherical to ellipsoidal and finally fibrous shape according to Utracki model. At the melt compounding/processing temperature of 230°C, the R-PET phase was in semi solid state and hence it formed fibrous morphology in the PP melt which was confirmed by SEM analysis. The most interesting finding was that crystallization of both the component polymers was affected due to the presence of the other. R-PP showed nucleation effect in presence of R-PET with the shift in Tc from 118°C to higher temperature side (123°C). Even R-PET exhibited shift in the Tc from 178°C to 201°C in presence of R-PP. These results are discussed in terms of nucleation and slow heat dissipation for PET domain in PP melt together with shear induced crystallization. These structural modifications in the R-PP/R-PET blends led to improvement in properties at certain compositions processed under certain conditions.

Because of potential reduced cost and improved retained conductivity, high viscosity friction reducers (HVFRs) are becoming increasingly popular in hydraulic fracturing stages where linear or crosslinked guar gels are traditionally used. However, concerns remain regarding the proppant transport capability of HVFRs relative to that of traditional linear gels. To address these concerns, the proppant transport capability of a polyacrylamide-based HVFR is compared with that of linear guar at cost-parity concentrations. Correlation between the proppant transport capability and rheological properties of the fluids, including viscosity and elasticity, is also discussed. A slot flow device was used to visualize the proppant transport performance of each fluid. The fluid concentrations ranged from 2.25 to 4.5 gpt (gallons per thousand gallons) for the HVFRs and 15# to 30# (pounds per thousand gallons) for guar, which were matched to achieve cost-parity between the two classes of fluids. The proppants used were 30/50, 20/40, and 12/20 mesh sand at 2 ppg (pounds per gallon) loading. Comprehensive rheological properties of the carrier fluids were characterized under steady-state and oscillatory shear and correlated with the observed proppant transport behavior. At least two sand transport mechanisms were observable in the slot flow tests. Small sand particles remained suspended in the fluid and were transported by convection. Large sand particles settled quickly, but top layers of the settled particles crept forward at a slower speed. The HVFR showed significantly better sand transport efficiency than guar at cost-parity concentrations despite the fact that the HVFR had a lower viscosity at high shear rates. The improved sand transport performance may be attributed to two factors: first, sand particles were suspended for a longer time in the HVFR because of its elevated viscosity at lower shear rates in the center of the slot; second, the HVFR's increased elasticity in the high shear regime near the wall further enhanced sand suspension by providing an elastic lifting force to hinder sand settling. The elastic effect on sand settling is estimated to be much larger than the viscous effect for the HVFR investigated herein but is neglibile in guar. Field results validated the capability of the HVFR to carry proppants, including 20/40 mesh coarse sand, in situations where traditional slickwater FRs and linear guar gel failed. This study demonstrated that the HVFR has superior proppant transport capability, relative to guar, at cost-parity concentrations despite having lower viscosity at high shear rates. The results indicate that the proppant transport performance of fracturing fluids correlates better with their elasticity and low shear viscosity than the high shear viscosity. Additionally, the findings provide much needed proppant transport data for field engineers to make rational choices for the selection of fracturing fluids.

The ability to assess rheological properties of neat cement grout, such as those used in structural repair and for filling post-tension ducts, is of special interest for the evaluation of the ease of pumping, spreading into place, and filling of narrow spaces. There is an increasing need to identify dependable and simple test methods that can characterize the consistency of specialty cement grouts and reflect variations in rheological properties during handling and placement. Several tests can be used to evaluate the rheological characteristics of a cement grout suspension, including precise methods for the determination of rheological parameters and simple procedures to assess fluidity. Rheological properties can be accurately determined by using a coaxial cylinder viscometer. However, the use of such a viscometer is mainly limited to the laboratory, and simple methods including the mini-slump spread and the modified Marsh cone tests are usually employed in the field to verify the consistency for quality control. This paper attempts to establish relationships between rheological parameters and fluidity values obtained using simple test methods. Relationships are also determined between the wash-out resistance of structural cement grout and various fluidity and rheological parameters. The derived relationships are based on a wide variety of cement grouts covering up to 210 data points. The various grouts were prepared with W/C ranging between 0.30 and 0.50, Type I and III portland cements, as well as various silica fume replacement values (up to 8% by mass), blast-furnace slag contents of 20 to 60%, fly ash substitutions of 10 to 30%, and limestone filler replacements of up to 30%. The investigated grouts incorporated melamine- and naphthalene-based high-range water reducer, welan gum and cellulose-based viscosity-modifying admixtures, as well as set-retarding admixture. Test results highlight the difficulties of relying on a single empirical test to evaluate the fluidity of a given grout. Correlations between various simple measurements of fluidity and wash-out mass loss and apparent viscosities determined at different shear rates indicate that the mini-slump and wash-out mass loss measurements correspond well to viscosities determined at low-shear rates (5.1 s-1). In contrast, the modified Marsh cone measurement corresponds well to viscosity determined at high-shear rates ranging between 340 and 510 s-1. Because of the pseudo-plastic behavior of structural cement grouts, field quality control tests should include fluidity assessment at low and high shear rates to adequately evaluate the rheological behavior of the grouts.

Whole blood viscosity in microvascular angina and coronary artery disease: Significance and utility

Hemorheologic profile in healthy women undergoing controlled ovarian stimulation

The current investigations are related to presenting the characteristics of flow at very high and low shear rates along with the melting process over the geometry of Riga plate. Carreau nanofluid is most appropriate mathematical viscosity model that can deal with low and high shear rates. Transportation of energy is discussed through melting conditions, thermal radiation and viscous dissipation. In this study, electromagnetic hydrodynamic aspect of nanofluid is discussed by using electromagnetic surface (Riga plate) and this system generates Lorentz force parallel to wall that keeps its effect on velocity of nanofluid. Partial differential equations (PDEs) are moved in ordinary differential equations and numerical approach named Keller Box and Shooting scheme are exercised to fetch the numerical solution of the system. An augmentation in Q leads to an enrichment in an external magnetic field. The velocity as well as momentum boundary layer booms by the virtue of an improvement in an external magnetic field. The viscosity of the nanofluid increases by the virtue of a magnification in β. Nanofluid becomes more radiated and absorbs more heat as a result of magnification in Nr, which escalates the heat transfer rate.

Views Icon Views Article contents Figures & tables Video Audio Supplementary Data Peer Review Share Icon Share Twitter Facebook Reddit LinkedIn Tools Icon Tools Reprints and Permissions Cite Icon Cite Search Site Citation Edward J. Stancik, Anne L. Hawkinson, Jan Vermant, Gerald G. Fuller; Dynamic transitions and oscillatory melting of a two-dimensional crystal subjected to shear flow. Journal of Rheology 1 January 2004; 48 (1): 159–173. https://doi.org/10.1122/1.1631425 Download citation file: Ris (Zotero) Reference Manager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentThe Society of RheologyJournal of Rheology Search Advanced Search |Citation Search

The spatial organization of particles in a colloidal gel controls the macroscopic properties, such as the rheological ones or the macroscopic gel stability. However, the suspension microstructure depends in a non-trivial manner on the colloidal interactions, the concentration and the flow history. Especially the effect of the latter is so far ill-understood and difficult to study in bulk suspensions. In the present work, well-characterized two dimensional suspensions are used to study the flow-induced structure in colloidal gels. Both a parallel band apparatus and a four roll mill are used to generate surface flows and the resulting steady state structures are analyzed using video microscopy. Because of the 2D nature of the suspensions, a high temporal and spatial resolution can be obtained, rendering the visualization for a wide range of surface coverages and flow rates possible. In this wide parameter space, two different regimes can be distinguished. At low surface coverages or high shear rates, only isolated flocs exist, whereas at high surface coverages or low shear rates, a transient network structure is encountered. In the two micro structural regimes the evolution of the characteristic length scales, the dominant orientation and anisotropy and the local aggregate or cluster densities is investigated. For individual aggregates, a simple analysis of hydrodynamic forces on the aggregates is used to evaluate the shear rate dependence of the aggregate size and aggregate density.

The electrorheology (ER) of suspensions based on polystyrene/polyaniline (PS/PANI) core/shell structured microspheres and those based on disk-like zeolite particles at different electric fields and particle volume fractions have been studied, respectively. Both types of ER fluids showed abrupt shear thickening under high electric fields and low shear rates, as well as shear thinning when the shear rate increased. A normalized method that considers the effects of electric field strength, shear rate and particle volume fraction was proposed to compare the rheological curves of the two ER fluids. The curves evaluated from the normalization method showed similar shear thinning at low shear rates and the hydrodynamic effect at high shear rates. Shear thinning represents the structure destroyed by shearing, and shear thickening at low shear regions indicates the dramatic structure change. The particle volume fraction and structure factor effects demonstrate that the mechanical contact between particles and the wall of the electrodes is crucial to the shear strength of ER fluids, indicating an electric/magnetic field modulated friction mechanism of the ER and magnetorheological (MR) effects.

Shear and extensional deformation are two basic rheological properties which occur during food manipulation, mastication, deglutition executed during oral consumption and also in the processing and packaging of foods. Fluid resistance against shear and extensional deformation differ widely and whilst this has been confirmed theoretically and experimentally, a clear understanding of human perception of these properties will have beneficial returns to the food industry in designing and manufacturing of high quality, nutritious food to suit consumers' need (Laguna, Aktar, Ettelaie, Holmes, & Chen, 2016).

Field data from polymer flooding operations sometimes indicate a better-than-expected polymer injectivity below fracturing pressure. Current interpretations for this unexpected phenomenon are based either on geomechanical considerations (for unconsolidated sand formations) or on polymer mechanical degradation, potentially occurring in the injection facilities and the near wellbore area. In this paper, a new approach of polymer injectivity is suggested. It is based on the study of polymer mechanical degradation with respect to both shear and extensional viscosities. In the first part of this work, we have investigated the onset of mechanical degradation by submitting semi-dilute solutions of high molecular weight partially hydrolyzed polyacrylamide (HPAM) to extensional laminar flow created by an API capillary system. We have then measured both shear and extensional viscosity of the native and the degraded HPAM solutions. We consider the onset of mechanical degradation to be reached when shear viscosity loss is equal to 10%. At low degradation rate, shear viscosity is unaffected while extensional viscosity decreases up to 30%, whereas, at higher degradation rates, shear viscosity drops by 10% (onset) while extensional viscosity is reduced up to 60%. This means that degraded HPAM with weakly affected shear viscosity can develop much less resistance to extensional flow. In the second part, we have explored the influence of mechanical degradation on injectivity by determining resistance factors of native and degraded HPAM solutions. Solutions have been injected in reproducible unconsolidated sand packs. At low velocities, resistance factors were similar for both kinds of solutions, as expected from their comparable shear viscosities. However, at high velocities, namely where flow in porous media implies high extensional deformations in the vicinities of the pore throats, apparent rheo-thickening was much less marked for solutions degraded at high extensional rate. These results allow understanding why polymers which do not seem to be mechanically degraded according to their shear viscosity can show a very good injectivity, thanks to the reduction of extensional resistance in porous media. They could also lead to establish guidelines for designing new polymer pre-treatment methods aimed at improving injectivity while retaining the mobility control ability of polymers.

Transfusion Therapy Decreases Oxygen Transport to Low-Flow Vascular Beds in Sickle Cell Disease.

Assessing low shear viscosity as the new bitumen Softening Point test