Apparent Viscosity Values Research Articles

Flow Properties of Montmorillonite Suspended in Water with Surfactant

Abstract The flow properties of montmorillonite, one of the main clay components in coal, were studied in water suspensions to clarify the origins of the Bingham flow properties of coal water slurry (CWM) in the presence of a surfactant. The addition of anionic surfactants, such as sodium poly(isoprenesulfonate) and sodium polycarbonate, significantly decreased the apparent viscosity and Bingham yield value of the montmorillonite suspension, although the latter value never became zero, even when a large quantity of surfactant was added. The amount of water bound to montmorillonite particles, measured using 1H NMR, was found to increase with the addition of a surfactant. The Bingham yield value and the relative viscosity of the montmorillonite suspension were described by Michaels’ equation, τB = A(Sφ − Sφ0)3 (Eq. 6), and by the modified Brinkman’s equation, ηr = (1 − Sφ)−k (Eq. 8), respectively. In both equations, the sum volume of montmorillonite particles and its bound water (Sφ) is correlated to the flow properties through constants A and k. A reduction of both A and k suggests two different actions of the anionic surfactants in the montmorillonite suspension. A decrease in the A value indicates a reduction of the strength of the aggregate networks of montmorillonite at a low shear rate, while a decrease in the k value shows that the shape of the effective montmorillonite particle becomes more spherical due to an increase of bound water.

Apparent viscosity of particulate solids determined using creepanalysis

Creep compliance measurements were used to quantify the ability of a range of materials to undergo plasticdeformation. Dibasic calcium phosphate dihydrate, anhydrous lactose, sodium bicarbonate, sodium chloride, partially pregelatinised corn starch and two types of microcrystalline cellulose represented materials with principal consolidation mechanisms ranging from brittle fracture to extensive plastic deformation. As the porosity of a compact decreased, apparent viscosity increased due to increasing resistance to viscous flow. An exponential relation was shown between apparent viscosity and porosity. Test conditions, including the porosity of the sample, should be specified when quoting a value of apparent viscosity derived from such tests.

Indentation Creep of Hydrated Soda–Lime Silicate Glass Determined by Nanoindentation

Time‐dependent deformation behavior was investigated for soda–lime silicate glass with various water contents, using a nanoindentation technique. The complete indentation curve, loading and unloading part, is analyzed. It is shown that this deformation behavior may be represented in terms of a simple mechanical model analogous to a viscoelastic system. Values for Young's modulus were derived, a retardation spectrum was deduced, and apparent viscosity values were calculated. Structural rearrangements of the glass appear to be responsible for the observed changes of the viscoelastic properties. Water in the glass reduces Young's modulus and yield stress and thus promotes viscous flow.

The Al project—an overview

A test fluid of polyisobutylene in decalin was prepared and sent to a number of laboratories around the world. A workshop was held in France to compare the results of experiments on this fluid in shear and extension. In steady shear flow, excellent agreement on values of apparent viscosity and first normal stress difference as functions of shear rate was obtained between the laboratories. The data were fitted to a Carreau-Yasuda equation at each temperature. Shift factors relating the data at any particular temperature to that at the reference temperature of 20°C were fitted to the Williams-Landel-Ferry (WLF) equation. Further good agreement was obtained between the laboratories on values of η' and G' with frequency. Data on combined steady and oscillatory shear flow are presented. The results of several different types of elongational experiments are given, and the methods are compared. Agreement within classes of experiment was fair, and most experiments showed a similar trend in the variation of transient elongational viscosity as a function of strain rate. A number of other types of flow were presented at the workshop, and are discussed.

Stability of Couette flow of liquids with power law viscosity

The stability of the Couette flow of the liquid with the power law viscosity in a wide annular gap has been investigated theoretically in this work with the aid of the method of small disturbances. The Taylor number, being a criterion of the stability, has been defined using the mean apparent viscosity value in the main flow. In the whole range of the radius ratio, Ri/Ro and the flow index, n, considered (Ri/Ro ≥ 0.5, n = 0.25–1.75 ), the critical value of the Taylor number Tac is an increasing function of the flow index, i.e., shear thinning has destabilizing influence on the rotational flow, and dilatancy exhibits an opposite tendency.

Viscosity of dilute polyelectrolyte solutions: Temperature dependence

The reduced specific viscosity of fully sulfonated sodium neutralized polystyrene under ‘‘free salt’’ conditions was investigated as a function of temperature. It was found that the position of the maxima is strongly dependent on temperature. Small temperature changes (ΔT=20 K) introduce shifts of two orders of magnitude in the polyelectrolyte concentration at which the maximum appear. At a given temperature Cpmax is linearly dependent on molecular weight, the slope of the linear plot is temperature dependent increasing with temperature. The value of Cp at the maximum increases linearly with concentrations of externally added salt at all temperatures and molecular weights. At a given molecular weight, the logarithm of Cpmax is inversely dependent on temperature. The activation energy was calculated and found to be independent of the molecular weight of the polyelectrolyte. The dependence of the reduced specific viscosity on normalized polyelectrolyte concentration (Cp/Cpmax) resulted in one ‘‘master curve’’ for all temperatures at a given molecular weight. Below the maximum, at lower polyelectrolyte concentration, a linear dependence of ηsp/Cp on Cp was obtained even for salt-free solutions. The apparent intrinsic viscosity and the Huggins coefficient were calculated, as it is done for noncharged polymers in the linear regime. High values of apparent intrinsic viscosity and the Huggins coefficient were obtained. The high measured values cannot be explained by hydrodynamic contribution of fully stretched molecules, indicating that even at extremely high dilutions the main contribution is the one of long range interactions (Culombic or others). The dependence of the apparent intrinsic viscosity on molecular weight was established. These measurements could be performed thanks to the availability of the apparatus developed by us which makes possible accurate measurements of the shear viscosity of low ionic strength, dilute polyelectrolyte solutions, down to polymer concentrations below one part per million.

Heat transfer pseudoplastic fluids in plate-type heat exchangers.

Experimental studies of heat transfer and pressure drop in a plate-type heat exchanger were carried out for pseudoplastic fluids.Representative values of shear rate and apparent viscosity in the exchanger were estimated by a simple model. It was found that the previous correlations of heat transfer coefficient and pressure drop for Newtonian fluid can be extended to pseudoplastic fluids by the introduction of these representative values.

Mass transfer in the spiral flow of a pseudoplastic liquid

The rate of mass transfer in the spiral flow of pseudoplastic liquids is experimentally investigated. The results are correlated with the usual dimensionless parameters calculated on the basis of the mean apparent viscosity value. The rate of mass transfer in the flow with Taylor vortices can be described by a correlation formulated for Newtonian liquids. This conclusion is also valid for heat transfer in the spiral flow of pseudoplastic liquids.

Movement of Entamoeba histolytica trophozoites in rat cecum and colon intact mucus blankets and harvested mucus gels.

Entamoeba histolytica trophozoites were centrifuged into mucus gels harvested from in vivo loops of rat cecum and proximal colon. Frank ameba movement was not detected in the colonic mucus, but attenuated motility was measured in the cecal mucus. The harvested rat cecal mucus had significantly lower apparent viscosity and neutral glycoprotein concentration values than the colonic mucus. A shape factor method was developed to assess the motility of amebae in mucus gels and intact mucus blankets. Shape factor data obtained from harvested mucus gel and intact mucus blanket experiments indicated that such mucus severely attenuated trophozoite movement with the attenuation being greater with colonic than with cecal mucus. Entamoeba trophozoites are known to be able to generate a pseudopod force of 3.3 x 10(-6) Newtons. Latex microspheres of the size range of Entamoeba trophozoites were forced through cecal and colonic mucus gels under gravity. Colonic mucus gels could withstand a force of 3.3 x 10(-6) Newtons while cecal mucus could not, suggesting that the ameba movement that was observed in cecal mucus involved mechanical penetration of the mucus by the ameba pseudopodia and did not require prior gel dissolution by Entamoeba enzymes.

Theoretical and experimental study of the time dependent flow of red blood cell suspension through narrow pores.

The Hemorheometer has been adapted to allow the recording of the flow rate during the filtration process. For newtonian fluids, the flow rate variation versus time through the pores is well approximated by Poiseuille's law. For dilute red blood cell suspensions, the same analysis can be applied by introducing the concept of "apparent filtration viscosity" which is higher than the usual viscosity measured by Couette viscometry. The apparent filtration viscosity parameter is related to the deformations undergone by red blood cells as they pass through the narrow pores. Apparent filtration viscosity can be used to obtain a precise determination of the erythrocyte deformability. Measurements performed, for a given blood sample, with pores of different diameters (5 microns, 8 microns and 12 microns) show that the error on the value of apparent filtration viscosity is less than 3%. As a result, the sensitivity of the filtration method allows to discriminate among normal blood samples. High concentrations of erythrocytes or leucocytes are found to modify the apparent filtration viscosity. These factors are apparent in the recorded filtration curves. Their effects on filtration measurements can be easily estimated.

Thixotropic properties of whole blood from healthy human subjects.

The steady state non-Newtonian viscosity of whole human blood has been widely studied as a function of the shear rate; and used to characterize the blood in various pathological disorders. In our previous studies, we demonstrated that blood is a thixotropic fluid. Its time-dependency and shear rate dependency of rheological behavior can be represented by an equation developed by Huang. Parameters of the equation can be used for the characterization of an individual's blood. They provide information, such as the kinetic rate constant of breakdown of RBC rouleaux to individual erythrocytes and the relative amount of rouleau formation in the dynamic equilibrium between rouleaux and individual erythrocytes. In this communication, the thixotropic parameters from blood samples of fifteen apparently healthy human subjects were investigated. When compared to the use of apparent viscosity values for the correlation with a pathological disorder, thixotropic parameters are preferable. The mean values of thixotropic parameters obtained from apparently healthy human subjects provide a base for comparison with the same parameters as obtained from blood samples of patients with certain pathological disorders involving the circulation.

過共晶Al-Si合金の高速回転撹拌凝固における粘性流動とミクロ組織

An investigation was made on the viscous flow and microstructure in hypereutectic alloys by rheocasting with the rotation of a stirrer at a high speed in the range from 30 to 70 rev/s. The value of apparent viscosity in hypereutectic Al-Si alloys solidifying with the rotation of stirrer at a speed above 30 rev/s remained almost unchanged to a certain level except a rapid change in the initial stage of solidification. The average size of primary silicon was 66±19 μm in an Al-17%Si-4%Cu-0.5%Mg-0.3%Fe alloy ingot rheocast at 70 rev/s under the cooling condition of 0.6 K/s in the melt. The primary silicon size became finer by the modification of microstructure with an addition of 0.01%Na or 0.01 and 0.1%P in rheocast and conventionally cast hypereutectic Al-Si alloy ingots. A constant level of apparent viscosity was also observed during the high-speed rheocasting of an Al-17%Si-4%Cu-1.2%Fe-1%Mg-1%Ni-0.5%Mn-0.5%Zn-0.2%Ti-0.01%Na alloy ingot. It was depressed with the increase in stirrer speed from 30 to 50 rev/s. The primary silicon size of the alloy ingot was 101±27 μm at a rotation speed of 30 s−1, 96±25 μm at 40 s−1 and 93±25 μm at 50s−1.

Autonomic regulation of viscoelasticity of cat tracheal gland secretions.

The purpose of this study was to determine whether various adrenergic agonists selectively regulate the viscoelastic properties of the stimulated secretions from airway submucosal glands. Nanoliter quantities of cat tracheal secretions before and during each of three stimuli were collected directly from a single submucosal gland with a micropipette, and the viscoelastic properties of the secretions were determined using a newly developed capillary microrheometer. Under unstimulated conditions (control), the measured values of apparent viscosity and elasticity of the secretions were more reproducible than the values obtained in previous studies in which samples were collected by other methods. After muscarinic (acetylcholine), alpha-adrenergic (phenylephrine), or beta-adrenergic (isoproterenol) stimulation, the submucosal gland's secretory rate was, in each case, greater than control. The viscoelastic properties of the secretions induced by muscarinic stimulation, however, were identical to control, whereas alpha-adrenergic stimulation produced secretions of a lower apparent viscosity, and beta-adrenergic stimulation produced secretions of a higher apparent viscosity and lower elasticity than control. Thus autonomic agonists selectively regulate the viscoelastic properties of submucosal gland secretions from cat trachea.

Problems in Using Apparent Viscosity to Select Pumps for Pseudoplastic Fluids

ABSTRACT USING an apparent viscosity value and assuming Newtonian flow behavior is a commonly practiced method of estimating pressure losses for the flow of pseudoplastic (shear-thinning) fluids in tubes. This procedure may lead to significant over or under estimation in pressure loss and power requirements depending on the rate of shear at which the apparent viscosity is determined. These problems may result in large errors in analyzing the performance of fluid handling systems and lead to improper sizing of pumps and motors.

Production of Extracellular Polysaccharide by Zoogloea ramigera

In batch cultures of Zoogloea ramigera the maximum rate of exopolysaccharide synthesis occurred in a partly growth-linked process. The exopolysaccharide was attached to the cells as a capsule. The capsules were released from the cell walls after 150 h of cultivation, which caused the fermentation broth to be highly viscous. Ultrasonication could be used to release capsular polysaccharide from the microbial cell walls. Treatment performed after 48 to 66 h of cultivation revealed exopolysaccharide concentration and apparent viscosity values in accordance with values of untreated samples withdrawn after 161 h of cultivation. The yield coefficient of exopolysaccharide on the basis of consumed glucose was in the range of 55 to 60% for batch cultivations with an initial glucose concentration of 25 g liter. An exopolysaccharide concentration of up to 38 g liter could be attained if glucose, nitrogen, and growth factors were fed into the batch culture. The oxygen consumption rate in batch fermentations reached 25 mmol of O(2) liter h during the exopolysaccharide synthesis phase and then decreased to values below 5 mmol of O(2) liter h during the release phase. The fermentation broth showed pseudoplastic flow behavior, and the polysaccharide was not degraded when growth had ceased.

Approche du mécanisme de gélification des sols d'agarose I. Evolution des caractéristiques rhéologiques des sols

Thermal rheological studies describe the flow properties of A37 agarose sols. Their behavior displays plastic flow as shear strain increases. Rheological characteristtcs, viscosity, apparent viscosity and yield value are measured. Their variations with decreasing temperature pathway followed structural changes within the gelling process. A thixotropic flow occurred at the sol-gel transition point. The concentration of polymer in the gel is related to the absolute temperature of gelification in order to evaluate the heat of crosslinking. The high value corroborates the assumption of the crystalline nature of agarose gels.

Stability of Concentrated Crude Oil-In-Water En1ulsions As A Function of Shear Rate, Temperature And Oil Concentration

Abstract Emulsions were prepared with a California crude oil and tap water by stabilizing with a nonionic emulsifier (Triton X-114). Their rheological properties were studied as a function of composition, temperature and shear rate. Those having high concentrations of the dispersed phase behaved like pseudoplastic fluids. Apparent viscosity or consistency increased with the concentration of the dispersed phase and decreased with temperature. ASTM plots of kinematic viscosity VB temperature were linear for each emulsion. Viscosity corrections for temperature could be made for the W/O emulsions, but not the O/W ones, from a knowledge of the viscosity temperature relationship for the oil and a single value of the emulsion's apparent viscosity. The inversion of O/W emulsions to form W/O ones may be predicted by an empirical equation relating oil concentration, temperature and shear stress. Introduction EMULSIONS are dispersions of oil droplets in water or water droplets in oil. We are all familiar with them in our every-day life, and we are particularly aware of them in the oil industry. Many crude oils are produced as emulsions and some of the major products of our industry are sold as emulsions. They form an important area of technology as well as an interesting subject of science. In the oil production industry, emulsions are looked on with disdain because they are often an expensive, bothersome problem. However they do have properties which can, with wisdom, be used to advantage. Simon and Poynter(1) as well as others (2,3) have shown how produced water-in-oil (W/O) emulsions can be converted to oil-in-water (O/W) ones to achieve many advantages, Emulsions or dispersions of crude oil in water or brine have been successfully used in some pipeline transportation systems (1) and have been proposed for others(5,6). In these latter cases, we take advantage of the relatively low flow resistance of the continuous aqueous phase compared to that of the oil phase, particularly at arctic temperatures. For this reason, it is very important to maintain water or brine as the continuous phase. Under some conditions, one type of emulsion will invert or change into the other type. By chemical means, Simon and Poynter were able to invert the highly viscous, naturally produced W/O emulsions into the much more fluid O/W ones. They also noted in their paper that increased shear and1or increased temperature would cause an inversion of three O/W emulsions back to W/O ones. This latter observation prompted us to question the stability of emulsions in pipelines where shear is very high. Evidently it has not been a problem for pipelines carrying waxy crude oil-in-water dispersions at temperatures well below the pour point of the crude oil(4), where inversion is difficult to visualize. The effect of temperature suggests that it may not be a problem at ambient arctic temperatures. The purpose of this study was first to determine the rheological properties of emulsions containing different amounts of crude oil at different temperatures.

Chemically Modified Natural Gum for Use in Well Stimulation

Abstract A new polymer gelling agent has been developed to help satisfy the growing demand for "clean" hydraulic fracturing fluids. This polymer is a guar derivative that exhibits the desirable characteristics of conventional guar and that leaves low residue upon breaking. The derivatized guar was evaluated for its ability to function as a fracturing-fluid gelling agent in comparison with both a conventional guar and a nonionic cellulose derivative. The guar derivative possesses a number of advantages over both the conventional guar and the cellulose derivative. Laboratory experimental data and field results are presented. Introduction Hydraulic fracturing has been used successfully for oil- and gas-well stimulation for about 27 years. During this time the size of the treatments has grown from the original "tank of oil and sack of sand" to the current massive hydraulic fracturing treatments, entailing several hundred thousand gallons of fluid and large amounts of sand. These massive treatments have become routine in some areas of this country. Although many types of fluids have been used successfully, aqueous fluids have been preferred recently. Because of economic and safety considerations, aqueous fluids will likely continue to be preferred. Treatment designs usually require that the fluids possess a particular apparent viscosity. These stipulated viscosities are particular apparent viscosity. These stipulated viscosities are often many times higher than that of the base fluid in its natural state. The increased apparent viscosities are generally attained by the addition of hydrophilic polymeric "gelling agents." A variety of gelling agents for aqueous fluids is available. Each gelling agent possesses inherent chemical properties that often make it particularly applicable for a special function. These properties are a direct result of the chemical structure and stereochemistry of the repeating unit of the polymer, and the resulting conformation or macrostructure that the polymer assumes in the fluid. Polysaccharides, such as the guar polymer, possess many of the properties desired of a gelling agent. However, the relatively high percentage of insolubles (residue) present in commercial guar has been a matter of serious concern. Many believe that guar-gum residue can contribute to permanent formation and fracture conductivity damage. Because of the complexity of the situation, experimental evaluation of the over-all effect of this residue on the formation permeability and fracture flow capacity is difficult. However, there should be no question that the presence of the residue could result in damage to the formation and the proppant system, and that a reduction in the amount of residue proppant system, and that a reduction in the amount of residue present diminishes this possibility. present diminishes this possibility. A new low-residue, derivatized-guar (derivatized polysaccharide) gelling agent has been developed. This chemically polysaccharide) gelling agent has been developed. This chemically modified guar results in an 85-percent reduction in inherent residue over conventional guar gum, yet retains the desirable properties of the guar polymer. In addition, it provides an properties of the guar polymer. In addition, it provides an extension of guar chemistry and versatility into several new approaches for designing hydraulic fracturing fluids. This versatile polymer has application in most aqueous and polymer-emulsion hydraulic fracturing processes. polymer-emulsion hydraulic fracturing processes. In addition to possessing the obvious advantage of low residue, this new material can be dispersed controllably in aqueous fluids, thereby effectively reducing gel lumping tendencies. The result is a smooth, lump-free gel. It yields equivalent or slightly higher apparent viscosity values in fresh water and the usual brines compared with the old, conventional, guar-gum gelling agents. Alcohol tolerance of this new material is good, and it is readily complexed or crosslinked in water or alcohol-water mixtures with crosslinking agents. Fluids prepared with this new polymer may be manipulated to achieve temperature stability surpassing that of any gelled-water fracturing fluid containing the polysaccharides we have used in the past. SPEJ P. 5

ON THE RHEOLOGY OF MINCED MEAT

AbstractThe paper reviews research conducted by the author on the basic factors affecting the flow properties of beef muscle homogenates and meat emulsions having a bearing on sausage production. Apparent viscosity and yield value were measured using a coaxial cylinder viscometer. The homogenates show structural viscosity, plasticity and ‐ under certain conditions ‐ some thixotropy. The rheological behavior of homogenates is influenced by the time post‐mortem, pH, NaCl and added water. Sausage type emulsions are, in addition, influenced by the amount of added fat and the temperature. The results point to the following main factors as affecting the rheological properties of minced meat and meat emulsions: changes in the water holding capacity and swelling, changes in the interaction between myosin and actin, solubilization of myofibrillar proteins, and the physical state of fat.

Kinetics of structure build-up in self bodied emulsions stabilized by mixed emulsifiers

Ternary systems and emulsions prepared with anionic (sodium dodecyl sulfate), cationic (cetrimide), or nonionic (cetomacrogol) surfactants and cetostearyl alcohol were examined in creep and in continuous shear rheometry at the storage temperature of 25°C. Systems were tested frequently during the first 24 hr after preparation, and then regularly for 3 months. Creep tests were of short duration and the curves were analyzed to derive continuous spectra of retardation times. For each surfactant, the results obtained were correlated with the mechanisms by which gel networks formed. With age, anionic and cationic ternary systems and emulsions behaved similarly with respect to total compliances, retardation spectra, and continuous shear parameters. Additional structure, although not extensive, formed within the first 2 hr storage. This was indicated in creep by initial falls in total compliance values and decreases in the heights of retardation spectra, and in continuous shear by corresponding increases in apparent viscosities and hysteresis loop areas. Thereafter negligible new structure formed, and thus retardation spectra for systems tested after 2.5 and 24 hr storage were similar, and there was little variation in total compliance, apparent viscosity, and loop area values. The essentially constant position of maxima in the retardation spectra indicated that the high temperature interaction which occurred during the preparation of ionic systems was the major mechanism which operated to form gel networks. The low temperature interaction occurring during the first 2 hr storage was insignificant. Cetomacrogol ternary system and emulsion behaved differently to the ionic systems. Structure built up rapidly during the first 24 hr storage. This was shown in creep by marked reductions in total compliances and retardation spectral values and in continuous shear by changing complex flow properties. The movement of maxima in the retardation spectra to longer times indicated that the mechanisms which operated to form gel networks at the storage temperature produced structures which differed at a molecular level to those formed at high temperatures.