scholarly journals Effect of Different Shear Rates on Particle Microstructure of Cementitious Materials in a Wide Gap Vane-in-cup Rheometer

Materials ◽  
2020 ◽  
Vol 13 (9) ◽  
pp. 2035
Author(s):  
Mahmoud Eslami Pirharati ◽  
Hans-W. Krauss ◽  
Carsten Schilde ◽  
Dirk Lowke
Keyword(s):  
Shear Rate ◽  
Rheological Properties ◽  
Cement Paste ◽  
Particle Agglomeration ◽  
Shear Rates ◽  
Average Shear ◽  
Local Shear ◽  
Wide Gap ◽  
Agglomeration State ◽  
Shear History

Rheological properties of cementitious suspensions are affected not only by their mixture composition but also by process-related factors such as shear history. To enable a model-based description, investigations were carried out on the effect of shear history (shear rate variation over time) on the cement paste agglomeration state. Therefore, a Focused Beam Reflectance Measurement (FBRM) system and a wide gap rheometer were coupled to study the relation between shear history and in-situ chord length distribution simultaneously, indicating particle agglomeration. Hence, the effect of average shear rates (resulting from the applied shear profile), as well as shear rate distribution within the gap (local shear rates) on the particle agglomeration state have been investigated. The rheological properties of cement paste were evaluated with the Reiner–Riwlin approach. Furthermore, the agglomeration state of the particles was compared for different average shear rates and local shear rates at various positions of the FBRM probe. The results show that the median chord length increases in all positions when the average shear rate is decreased, indicating increasing particle agglomeration. Moreover, due to variable local shear rates at different FBRM probe positions, different agglomeration states are observed, resulting from two factors, shear rate dependent particle agglomeration and shear-induced particle migration.

scholarly journals Use of helical ribbon mixer for measurement of rheological properties of fruit pulps

2013 ◽  
Vol 19 (No. 4) ◽  
pp. 148-153 ◽  
Author(s):  
P. Novotná ◽  
A. Landfeld ◽  
K. Kýhos ◽  
M. Houška ◽  
J. Strohalm
Keyword(s):  
Shear Rate ◽  
Rheological Properties ◽  
Flow Behaviour ◽  
Rotational Rheometer ◽  
Shear Rates ◽  
Coaxial Cylinders ◽  
Helical Ribbon ◽  
Flow Behaviour Index ◽  
Average Shear ◽  
Behaviour Index

Fruit pulps contain fine particles of the flesh of the original fruit that are suspended in the fruit juice. This suspension has a tendency to settling or separation during measurements of its rheological properties in the rotational rheometer with coaxial cylinders (especially if the greater gap is used). In this case the use of a mixer is convenient. The mixer can serve as a tool for measurement of rheological properties and at the same time it can prevent the settling and it is not sensitive to the occurrence of greater particles in the measured fluid. The helical ribbon mixer was used in this work for measurement of five samples of fruit pulp. The mixer was calibrated by the use of Newtonian fluid of known viscosity (honey). The radius of the inner cylinder of hypothetical rotational rheometer was predicted from the assumption that mixer and cylinder exhibit the same torque necessary for the rotation at the same rotational speed. The average shear rate in the mixed pulp was predicted by using the relation valid for power law fluids and rheometer with coaxial cylinders. The radius (where the average shear rate was calculated) was chosen by the requirement that the shear rate would be almost independent of changes in the flow behaviour index valid for measured pulps. Firstly the flow behaviour index was predicted as a slope of torque vs. rotational speed dependence in log-log co-ordinates. It was found that the flow behaviour index varies in the range 0.2–0.3. The radius was predicted from a graph where shear rates for 0.2 and 0.3 are the same. Then the average shear rates were calculated from rotational speeds for individual flow behaviour indexes. Rheological properties measured by using a mixer correspond to those measured with a rotational rheometer with coaxial cylinders satisfactorily only in the case that the creeping flow regime was kept in the mixed fluid. The fruit pulps are strongly non-Newtonian fluids with very low values of the flow behaviour index around 0.2.

scholarly journals Soft channel formation and symmetry breaking in exotic active emulsions

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
L. N. Carenza ◽  
G. Gonnella ◽  
A. Lamura ◽  
D. Marenduzzo ◽  
G. Negro ◽  
...  
Keyword(s):  
Shear Rate ◽  
Rheological Properties ◽  
Self Assembly ◽  
Contractile Activity ◽  
Active Material ◽  
Fluid Flows ◽  
Shear Rates ◽  
Two Phases ◽  
The Stability ◽  
Isotropic Fluid

Abstract We use computer simulations to study the morphology and rheological properties of a bidimensional emulsion resulting from a mixture of a passive isotropic fluid and an active contractile polar gel, in the presence of a surfactant that favours the emulsification of the two phases. By varying the intensity of the contractile activity and of an externally imposed shear flow, we find three possible morphologies. For low shear rates, a simple lamellar state is obtained. For intermediate activity and shear rate, an asymmetric state emerges, which is characterized by shear and concentration banding at the polar/isotropic interface. A further increment in the active forcing leads to the self-assembly of a soft channel where an isotropic fluid flows between two layers of active material. We characterize the stability of this state by performing a dynamical test varying the intensity of the active forcing and shear rate. Finally, we address the rheological properties of the system by measuring the effective shear viscosity, finding that this increases as active forcing is increased—so that the fluid thickens with activity.

Development of Viscosified Acid-Surfactant Solutions for Oilfield Applications: Rheological Properties

2020 ◽  
Vol 143 (2) ◽  
Author(s):  
Lionel Talley Fogang ◽  
Muhammad Shahzad Kamal ◽  
Mohamed Mahmoud
Keyword(s):  
Shear Rate ◽  
Acid Solution ◽  
Rheological Properties ◽  
Calcium Chloride ◽  
Elastic Properties ◽  
Salt Concentration ◽  
Shear Thinning ◽  
Rate Range ◽  
Shear Rates ◽  
Surfactant Solutions

Abstract Viscosified acids are desired in several oilfield applications such as in acid diversion and acid fracturing operations. The study aimed to delineate the rheological properties of a novel amine type surfactant and viscosified acid-surfactant solutions. The steady shear and dynamic rheological properties were evaluated by varying the surfactant, acid, and salt concentration. Such a study is required to gauge the suitability of the viscosifying agent in acid stimulation jobs. The surfactant solutions without acid showed shear-thinning behavior, whereas those with acid showed a Newtonian plateau over a wide shear rate range before undergoing shear thinning. This means that over a wide shear rate range, the acid-surfactant solutions become independent of applied shear. At low shear rates, the viscosity of the surfactant was higher compared with the surfactant-acid solution. However, at high shear rates, the viscosity of the surfactant was lower compared with the viscosity of the surfactant-acid solution. There was an optimal salt concentration that improved the viscosity and elasticity of the acid-surfactant solutions. Thus, the rheology of the surfactant solution can be improved by adding both acid and salt. The elastic properties of acid-surfactant solutions were also better compared with the elastic properties of pure surfactant. The addition of acid improved the elastic properties of the surfactant solutions. Constant viscosity over a range of shear rate is a suitable application for acid fracturing operations in which the acid leak-off will be minimal due to the high viscosity. Also, brines in most of the carbonate formation consist of high loading of calcium chloride which was found to have a positive effect on the viscosity. Increasing the calcium chloride leads to an increase in viscosity, and then subsequently decreases the viscosity. This shows that the acid and salt concentration plays a role in modifying the rheological properties of the surfactant solutions.

scholarly journals Shear thinning and thickening of cemented paste backfill

2019 ◽  
Vol 29 (1) ◽  
pp. 80-93 ◽  
Author(s):  
Liuhua Yang ◽  
Hongjiang Wang ◽  
Aixiang Wu ◽  
Hong Li ◽  
Arlin Bruno Tchamba ◽  
...  
Keyword(s):  
Shear Rate ◽  
Rheological Properties ◽  
Yield Stress ◽  
Shear Thinning ◽  
High Shear ◽  
Cemented Paste Backfill ◽  
Concentrated Suspension ◽  
History Effects ◽  
Paste Backfill ◽  
Shear History

Abstract Cemented paste backfill (CPB) is considered to be a concentrated suspension in which tailings are bonded together by the hydraulic binder and water, and it has a high solid volume concentration (≥50 vol.%). Although the shear thinning and thickening of CPB has been extensively reported in literature, the shear history effects have been ignored in previous studies. In this paper, by using rheometer and Focused Beam Reflectance Measurement, the relationship between the rheological properties and microstructure of the paste under different shear histories was studied. The results have shown that at a low shear rate, CPB revealed shear thinning, low yield stress and low index parameters; while exhibited shear thickening, high yield stress and high consistency index when at high shear rates of shear history. This agreed with the general trends shown in the FBRM analysis. It was proposed that the action of shear is beneficial to particle dispersion, whereas a high shear rate history tends to promote the aggregation of particles. It was revealed that both shear thinning and thickening of paste are related to the situation of particles (flocculation, dispersion and aggregation), and shear history effects play an important role in rheological properties of CPB.

A Comparison of Rheological Models and Experimental Data of Metallocene Linear Low Density Polyethylene Solutions as a Function of Temperature and Concentration

2016 ◽  
Vol 12 (3) ◽  
pp. 4322-4339
Author(s):  
Salah Hamza
Keyword(s):  
Experimental Data ◽  
Shear Rate ◽  
Rheological Properties ◽  
Power Law ◽  
Low Density Polyethylene ◽  
Effect Of Temperature ◽  
Low Density ◽  
Linear Low Density Polyethylene ◽  
Shear Rates ◽  
Wide Range

Knowledge of rheological properties of polymer and their variation with temperature and concentration have been globally important for processing and fabrication of polymers in order to make useful products. Basheer et al. [1] investigated, experimentally, the changes in rheological properties of metallocene linear low density polyethylene (mLLDPE) solutions by using a rotational rheometer model AR-G2 with parallel plate geometry. Their work covered the temperature range from  to  and  concentration from  to . In this paper, we reconsider Basheer work to describe the rheological behavior of mLLDPE solutions and its dependence on concentration and temperature.Until now, several models have been built to describe the complex behavior of polymer fluids with varying degrees of success. In this article, Oldroyd 4-constant, Giesekus and Power law models were tested for investigating the viscosity of mLLDPE solution as a function of shear rate. Results showed that Giesekus and power law models provide the best prediction of viscosity for a wide range of shear rates at constant temperature and concentration. Therefore, Giesekus and power law models were suitable for all mLLDPE solutions while Oldroyd 4-constant model doesn't.A new proposed correlation for the viscosity of mLLDPE solutions as a function of shear rate, temperature and concentration has been suggested. The effect of temperature and concentration can be adequately described by an Arrhenius-type and exponential function respectively. The proposed correlation form was found to fit the experimental data adequately.

Thixotropy of aqueous solution of fluorocarbon-modified poly(acrylic acid)

e-Polymers ◽  
2009 ◽  
Vol 9 (1) ◽  
Author(s):  
Hongqi Hu ◽  
Lin Li ◽  
Mingcai Chen
Keyword(s):  
Aqueous Solution ◽  
Shear Rate ◽  
Acrylic Acid ◽  
Rheological Properties ◽  
Great Increase ◽  
Hydrophobic Association ◽  
Chain Elongation ◽  
Shear Rates ◽  
Viscosity Dependence ◽  
Poly Acrylic Acid

AbstractThe rheological properties of the aqueous solution of 1H,1H,11Hperfluoroundecyl acrylate -modified poly(acrylic acid) were studied. It was found that the solutions show different viscosity dependence on shear time at different pH and shear rates. At lower pH and moderate shear rates, the viscosity of the solutions shows a great increase with time. At pH 5.0 and above, it exhibits thixotropy at any shear rate, i.e., the viscosity decreases with time at constant shear rates. If the shearing stops, the viscosity of the solutions can be recovered to some extent. These phenomena are interpreted to be due to the intermolecular hydrophobic association: the construction of the association leads to an increase of the viscosity, the destroying of the association leads to a decrease of the viscosity. The pH-induced conformational change and the shearing-induced chain elongation jointly influence the intermolecular hydrophobic association.

Evaluation of New Methods and Measuring Systems for Characterisation of Flow Behaviour of Complex Foods

2006 ◽  
Vol 16 (1) ◽  
pp. 19-25 ◽  
Author(s):  
H. Roos ◽  
U. Bolmstedt ◽  
A. Axelsson
Keyword(s):  
Shear Rate ◽  
Concentric Cylinder ◽  
Measuring Systems ◽  
Tomato Paste ◽  
Concentric Cylinders ◽  
Fruit Samples ◽  
Average Shear ◽  
Wide Gap ◽  
Narrow Gaps ◽  
Constant Shear Rate

Abstract Conventional methods often impose difficulties when measuring the viscosity of fluids containing particles or fibres, e.g. tomato paste or fruit preparations, mainly due to the narrow gaps of the viscometer. In order to solve these problems different geometries have been developed, e.g. different mixer systems and wide gap double concentric cylinders. However, these can not be evaluated assuming a constant shear rate throughout the fluid. In this study, three different kinds of mixer systems have been studied; a small and a large paddle and a helix. For the mixer systems an average shear rate must be determined and a quotient between torque and shear stress must be found. In addition, a wide gap double concentric cylinder (DCC) was examined and evaluated using two different methods. When evaluating the mixer systems a method based on the Couette analogy has been used successfully for a number of complex fluids, including prepared sauces and fruit samples containing particles of different size. The DCC has been evaluated using a numerical as well as an approximate method, both giving results of good accuracy. All systems had the limitation that no consistent results were obtained for tomato paste. However, when starch was added to the diluted tomato paste dispersion, satisfying results were once again obtained.

scholarly journals Rheological properties of traditional balsamic vinegar: New insights and markers for objective and perceived quality

2017 ◽  
Vol 6 (1) ◽  
Author(s):  
Pasquale M. Falcone ◽  
Elisa Sabatinelli ◽  
Federico Lemmetti ◽  
Paolo Giudici
Keyword(s):  
Shear Rate ◽  
Rheological Properties ◽  
Dynamic Viscosity ◽  
Flow Instability ◽  
Relaxation Times ◽  
Sensory Properties ◽  
Flow Behaviour ◽  
Shear Rates ◽  
Wide Range ◽  
Balsamic Vinegar

The molecular structure of Traditional Balsamic Vinegar (TBV) undergoes shear-induced and time-dependent jamming transitions due to the high solute concentration and self-assembling phenomena of high molecular size melanoidins with very-long relaxation times (12 years at least or more than 25). The purpose of this work was to perform a descriptive and quantitativeevaluation of relationships between rheological properties, vinegar composition, and perceptual assessment of sensory properties according to the official sensory procedure. With this aim, vinegars having quality traits matching legal requirements for the PDO designation were analyzed for their reducing sugars (glucose and fructose), volatile acidity, fixed acidity, pH, Brix degree, and density as well as for their flow behaviour and dynamic viscosity over a wide range of shear rates. Results showed that flow behaviour of TBV was affected by jamming properties over wide-scale ranges of shear rate producing flow instability below a shear rate of 60s-1. Homogeneous, continuous flow was found at medium-high shear rates with thickening and/or thinning traits. A common onset for the structure scaling was mathematically estimated to occur close to when the density was 1.32 gmL-1. Comparative analysis of rheological, compositional and sensory properties suggested that the colloidal jamming of the vinegar melanoidins dominated the total olfactive and gustative stimuli, and determined the classification of the vinegars that had a higher dynamic viscosity but more homogeneous flow as being of the highest commercial quality category. A robust statistical model was proposed encoding for the top-down decision-making process for quality assignment according to the official sensory procedure, using composition and flow properties as predictor variables. 

Local Shear Conditions and Platelet Aggregates Regulate the Incorporation and Activity of Circulating Tissue Factor in ex-vivo Thrombi

2002 ◽  
Vol 88 (11) ◽  
pp. 822-826 ◽  
Author(s):  
Oana Vele ◽  
Yale Nemerson ◽  
Viji Balasubramanian
Keyword(s):  
Shear Rate ◽  
Tissue Factor ◽  
Ex Vivo ◽  
Minimal Amount ◽  
Chromogenic Substrate ◽  
Blood Samples ◽  
Shear Rates ◽  
Direct Demonstration ◽  
Local Shear ◽  
Platelet Aggregates

SummaryThe presence of thrombogenic blood-borne or circulating tissue factor (cTF) has recently been demonstrated. These observations have implicated cTF to be a key determinant of thrombus propagation by depositing on platelets in nascent thrombi. Previously, we detected cTF by detergent solubilization and addition of phospholipids. We now report the direct demonstration of TF activity in ex-vivo thrombi. Collagen-coated substrates were exposed to native blood at shear rates of 0, 650, and 2000 s-1 for 10 min in a modified rotating Teflon cone and plate viscometer. Substrates were then gently rinsed to remove ‘loose’ (unadherent) components of blood. cTF activity was measured by adding a solution containing 10 nM FVIIa, 100 nM FX, and 5 mM CaCl2 to the substrates exposed to blood. Samples of this mixture were obtained at intervals for 30 min and the amount of Xa generated was quantified by adding a chromogenic substrate, Spectrozyme Xa, and measuring the increase in OD at 405 nm. Our studies show that a minimal amount of generated Xa (∼ 1nM) can be measured from ex-vivo thrombi. Static and shear samples generated the same amount of Xa, with the exception of blood subjected to 650 s-1 shear. At 650 s-1 shear rate, the amount of Xa generated reached a maximum of 4 nM at 5 min and then decreased to ∼1 nM. Immunohistological stains and fluorescent images demonstrate the presence of cTF antigen at 650 s-1 wall shear rate.

scholarly journals Viscosity and Rheological Properties of Graphene Nanopowders Nanofluids

Entropy ◽  
2021 ◽  
Vol 23 (8) ◽  
pp. 979
Author(s):  
Abderrahim Bakak ◽  
Mohamed Lotfi ◽  
Rodolphe Heyd ◽  
Amine Ammar ◽  
Abdelaziz Koumina
Keyword(s):  
Shear Rate ◽  
Rheological Properties ◽  
Dynamic Viscosity ◽  
Volume Fraction ◽  
Solid Volume Fraction ◽  
Heat Extraction ◽  
Rheological Characterization ◽  
Shear Rates ◽  
Rheological Measurements

The dynamic viscosity and rheological properties of two different non-aqueous graphene nano-plates-based nanofluids are experimentally investigated in this paper, focusing on the effects of solid volume fraction and shear rate. For each nanofluid, four solid volume fractions have been considered ranging from 0.1% to 1%. The rheological characterization of the suspensions was performed at 20 ∘C, with shear rates ranging from 10−1s−1 to 103s−1, using a cone-plate rheometer. The Carreau–Yasuda model has been successfully applied to fit most of the rheological measurements. Although it is very common to observe an increase of the viscosity with the solid volume fraction, we still found here that the addition of nanoparticles produces lubrication effects in some cases. Such a result could be very helpful in the domain of heat extraction applications. The dependence of dynamic viscosity with graphene volume fraction was analyzed using the model of Vallejo et al.

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