Dependence Of Apparent Viscosity Research Articles

Probabilistic Assessment of Antarctic Thermomechanical Structure: Impacts on Ice Sheet Stability

AbstractUncertainty in present‐day glacial isostatic adjustment (GIA) rates represents at least 44% of the total gravity‐based ice mass balance signal over Antarctica. Meanwhile, physical couplings between solid Earth, sea level and ice dynamics enhance the dependency of the spatiotemporally varying GIA signal on three‐dimensional variations in mantle rheology. Improved knowledge of thermomechanical mantle structure is therefore required to refine estimates of current and projected ice mass balance. Here, we present a Bayesian inverse method for self‐consistently mapping shear‐wave velocities from high‐resolution adjoint tomography into thermomechanical structure using calibrated parameterisations of anelasticity at seismic frequency. We constrain the model using regional geophysical data sets containing information on upper mantle temperature, attenuation and viscosity structure. Our treatment allows formal quantification of parameter covariances, and naturally permits propagation of material parameter uncertainties into thermomechanical structure estimates. We find that uncertainty in steady‐state viscosity structure at 150 km depth can be reduced by 4–5 orders of magnitude compared with a forward‐modeling approach neglecting covariance between viscoelastic parameters. By accounting for the dependence of apparent viscosity on loading timescale, we find good agreement between our estimates of mantle viscosity beneath West Antarctica, and those derived from satellite GPS. Direct access to temperature structure allows us to estimate lateral variations in lithosphere‐asthenosphere boundary (LAB) depth, geothermal heat flow (GHF), and associated uncertainties. We find evidence for shallow LAB depths (63 ± 13 km), and high GHF (76 ± 7 mW m−2) beneath West Antarctica that, combined with low asthenospheric viscosities, indicate a highly dynamic response to ice mass loss.

Effects of water salinity on the foam dynamics for EOR application

Factors limiting foam injection for EOR application are exceptionally low rock permeability and exceedingly high salinity of the formation water. In this regard, foam formation using internal olefin sulfonate is investigated over a wide salinity range (1, 5, 8, 10, and 12% NaCl) through 10 mD limestone. The relationships between pressure drop (dP), apparent viscosity, liquid flow rate, total flow rate, salinity, foam texture, and length of foam drops at the outlet used as an indicator of viscosity are studied. Foaming is observed up to 12% NaCl, compared to a maximum of 8% NaCl in similar core-flooding experiments with 50 mD limestone and 255 mD sandstone. Thus, the salinity limit of foam formation has increased significantly due to the low permeability, which can be explained by the fact that the narrow porous system acts like a membrane with smaller holes. Compared to the increasing dP reported for highly permeable rocks, dP linearly decreases in almost the entire range of gas fraction (fg) at 1–10% NaCl. As fg increases, dP at higher total flow rate is higher at all salinities, but the magnitude of dP controls the dependence of apparent viscosity on total flow rate. Low dP is measured at 1% and 10% NaCl, and high dP is measured at 5, 8, and 12% NaCl. In the case of low dP, the apparent viscosity is higher at higher total flow rate with increasing gas fraction, but similar at two total flow rates with increasing liquid flow rate. In the case of high dP, the apparent viscosity is higher at lower total flow rate, both with an increase in the gas fraction and with an increase in the liquid flow rate. A linear correlation is found between dP or apparent viscosity and liquid flow rate, which defines it as a governing factor of foam flow and can be considered when modeling foam flow.

SIMULATING INJECTION MOLDING OF SEMI-CRYSTALLINE POLYMERS: EFFECT OF CRYSTALLIZATION ON THE DYNAMICS OF CHANNEL FILLING

Non-isothermal filling of a vertical round pipe with a non-Newtonian fluid is studied taking into account crystallization with first-type boundary conditions for a wall temperature. The liquid medium is considered as a semi-crystalline polymer fluid exhibiting rheological behavior described by the Carreau-Yasuda model. In addition, dependence of apparent viscosity on the degree of crystallinity is taken into account. Phase transition effects are described in accordance with the Avrami-Kolmogorov theory. Mathematical formulation of the problem includes equations of motion, energy, and continuity. Numerical solution of the problem is carried out using an original computational technique. As the pipe is being filled with a fluid, distributions of flow characteristics are shown with a distinguished crystallized layer on a solid wall.

Effect of high-pressure homogenization on the rheology, microstructure and fractal dimension of citrus fiber-oil dispersions

This study investigated the rheological properties, microstructure and fractal dimensions of the citrus fiber-oil dispersion. Different concentrations of citrus fiber (1.5%, 2.0%, and 2.5% w/w) were keeping the oil concentration at 0% (control) and 0.75% w/w. The dispersions were produced through high-pressure homogenization (HPH) at two pressures (80 and 160 MPa). The HPH process significantly increased the apparent viscosity, storage and loss moduli. But, the HPH reduced the activation energy associated with temperature dependence of apparent viscosity of dispersions. The microstructure of citrus fiber was significantly altered by the HPH process. The fractal dimension of dispersions produced through the HPH was close to 3.00 indicating that these dispersions were homogeneous and stable. These citrus fiber-oil dispersions produced using HPH will be preferentially used in food and pharmaceutical industry in the future.

Numerical Investigation of the Apparent Viscosity Dependence on Darcy Velocity During the Flow of Shear-Thinning Fluids in Porous Media

The viscosity exhibited by shear-thinning fluids within the interstices of a porous medium differs depending on pore dimensions and injection velocity. Therefore, predicting the macroscopic value of viscosity required as input to Darcy’s law is challenging and needs accurate identification of the characteristic microscopic dimensions dominating global pressure losses. The most common approach consists of defining an apparent “in situ” shear rate which can be used in the bulk constitutive equation of the fluid to predict viscosity during flow through the porous medium. The dependence of this apparent shear rate on Darcy velocity has traditionally been assumed to be linear, which is appropriate in the case of Newtonian fluids and power-law fluids. However, yield stress and plateau viscosities that can potentially affect such dependence are not captured by power-law model, so the linear assumption may lead to inaccurate viscosity predictions. For this reason, a set of two-dimensional (2D) flow problems were considered and solved numerically to assess the effects of the shear rheology model, the pore size distribution and the microstructural complexity on the value of the apparent shear rate. In order to facilitate the analysis, the microscopic features of all the investigated porous media were well characterized through pore network modelling. The present results prove the inability of traditional approaches to predict the macroscopic viscous pressure losses generated during the creeping flow of widely used Herschel–Bulkley and Carreau fluids. In particular, the existence of a yield stress or a plateau viscosity induces significant deviations from linearity in the relationship between apparent shear rate and Darcy velocity. The importance of these deviations is, in turn, shown to be highly affected by the dispersion of the pore size distribution and the degree of shear thinning. Moreover, the reasons for such observations are discussed using an analytical approach.

Rheological behaviour of chocolate at different temperatures

The rheological behaviour of the chocolate at different temperatures was studied using a concentric cylinder viscometer with precision small samples adapter, temperature sensor and standard spindle. BIO chocolate (100% organic cocoa) has been used for the whole types of experiments. At the first, the range of temperature has been chosen 36 °C, 38 °C, 40 °C, 42 °C, and 44 °C. The shear deformation rate was established from the 0.1 s-1 up to 68 s-1. Rheological behaviour was non-Newtonian (plastic) with inconsiderable yield stress in all temperatures. The chocolate unambiguously demonstrated plastic behaviour and flow curves were fitted by the power law model (Herschel-Bulkley model), Bingham model, and Casson model with taking into account the coefficient of determination R2. The obtained results of rheological behaviour of chocolate can be best described as Casson fluid. Exactly coefficients of models can be used for modelling of flow velocity, volume flow, friction factor, Reynolds number, two dimensional and three dimensional velocity profiles and much more for flow in the real technical elements e.g. pipes, trough, tubes. Finally, temperature dependence of apparent viscosity of chocolate was also continuously measured in the range from 35 °C up to 62 °C. The apparent viscosity decreased in the temperature range. This decrease was fitted using power law equation. The knowledge of the plastic flow behaviour of chocolate is very important, because it is not quite common flow behaviour of foodstuffs.

Ultrasound-assisted extraction of polysaccharides from Rhododendron aganniphum: Antioxidant activity and rheological properties

In this study, we aimed to optimize the extraction of polysaccharides from the leaves of Rhododendron aganniphum and investigate its rheological properties and antioxidant activity. After optimizing the operating parameters using a Box-Behnken design (BBD), the results showed that the optimal ultrasound-assisted extraction conditions were as follows: extraction temperature, 55°C; liquid-solid ratio, 25:1; extraction time, 2.2h; and ultrasound treatment power, 200W. The optimized experimental yield of polysaccharides by ultrasound-assisted extraction (PUAE) was 9.428%, higher than that obtained by hot water extraction (PHWE) for 12h at the same liquid-solid ratio and extraction temperature. In the in vitro antioxidant activity tests, PUAE had higher positive radical scavenging activity for hydroxyl, superoxide and 1,1-diphenyl-2-picrylhydrazyl (DPPH) radicals than PHWE. However, PUAE and PHWE solutions had similar intermolecular interactions in the steady-shear flow and dynamic viscoelasticity tests, resulting in similar macroscopic behaviour. With respect to the apparent viscosity, storage modulus (G′) and loss modulus (G″) of PUAE were lower at the same shear rate or angular frequency. All PUAE solutions exhibited non-Newtonian shear-thinning pseudoplastic behaviour that was accurately described by the Carreau model but was better fit by the power-law model at high shear rates (≥1/s), which demonstrated that the variation in the apparent viscosity dependence was greater at higher concentrations and shear rates. The G′ and G″ of the solutions increased as the experimental frequency increased from 0.05 to 500rad/s under all experimental concentrations, and the modulus crossover point decreased gradually with increasing PUAE concentration. The above results demonstrated that the ultrasound-assisted extraction methods gave a higher yield of polysaccharides from the leaves of R. aganniphum with a shorter extraction time than the hot water extraction method, which could affect the apparent viscosity and dynamic viscoelasticity. PUAE presented good radical scavenging activity for DPPH, superoxide and hydroxyl radicals in vitro and could be used as a natural antioxidant in the food and medical industries.

Thixotropic Behavior of Honey fromEucalyptusspp

Honey is a solution with high viscosity and most types of honey exhibit Newtonian behavior. However, some types show non-Newtonian features (thixotropy or dilatancy), which exerts influence on processing of the honey. The aim of this study was to evaluate the rheological properties of honey from Eucalyptus spp. The investigated samples of eucalypt honey originating from Italy or Australia were analyzed by the following methods: melissopalynological analysis, color on the Pfund scale, optical activity, water content and electrolytic conductivity. Rheological tests were carried out on a highly accurate device. The dependence of apparent viscosity on temperature and time was measured, and hysteresis loop tests were run. The dependence of shear rate on shear stress was described in accordance with the Herschel-Bulkley mathematical model. The rheological tests revealed the following: all samples exhibited non-Newtonian behavior and all were determined as thixotropic fluids. These results are discussed in relation to previous findings on the dilatant behavior of eucalypt honey. Practical Applications Knowledge of rheological properties of foodstuff is important for handling, processing and storing. The description of flow properties can indirectly offer information about the structure of the tested liquid. Most honeys behave as Newtonian fluids. However, there are exceptions such as heather or manuka honey. Eucalypt honey is also among these exceptions. Studies dealing with rheological properties of eucalypt honey are more than 60-years old. This study focused on rheological behavior of this type of honey and revised current knowledge.

An experimental study of rheological properties and stability characteristics of biochar-glycerol-water slurry fuels

The rheological behaviour and stability characteristics of biochar-glycerol-water slurry fuels were experimentally investigated, emphasising the effect of glycerol addition. A pine sawdust biochar with a size fraction of <32μm and a median particle size (D50) of approximately 12μm was used. A biochar-glycerol-water slurry fuel was prepared by dispersing biochar particles in a premixed glycerol/water solution as the suspending medium with glycerol content varying from 0 to 100wt%. 2wt% lignosulfonic acid sodium salt (LASS) (on the basis of dry weight of biochar) was added to the suspending medium as a dispersant. The effect of glycerol content on the rheological properties and stability characteristics of the slurry fuels were studied. The yield stress was measured with a Brookfield vane viscometer and the dependence of apparent viscosity and shear stress on the shear rate was characterised using a Haake VT550 cone and plate viscometer. The stability characteristics of the slurry fuels were characterised by using a “drop rod” method. As glycerol content increased, the maximum biochar loading decreased from 50 to 10wt% while the calorific values of the slurry fuels first increased and then decreased, reaching a maximum of 21MJkg−1 at 90wt% glycerol content. For a given biochar loading, increasing glycerol content increased the viscosity of the suspending medium and therefore the viscosity of the slurry fuels, displaying higher yield stress, more apparent shear-thinning behaviour and higher stability due to the enhanced flocculation of biochar particles.

Rheological Properties of Plastisols Based on Low-Toxicity Plasticizers

The rheological properties of plastisols based on low-toxicity plasticizers have been evaluated using a DV-79+ pro coaxial cylinder viscometer by steady shearing. The effect of plasticizer and temperature on the shearing rate dependence of apparent viscosity, non-Newtonian index ( n ) , as well as apparent activation energy ( Ea ) was investigated. The results indicate that all the plastisols prepared in this experiment show shear thinning pseudoplastic behavior before and after aging process. The plastisols prepared by DOTP shows an obvious shear thinning behavior than that of plastisols prepared by ATBC and DINCH. The dependence of viscosity properties on temperature of plastisols accord with Arrhenius formula except DOTP-based system, and the apparent activation energy of plastisols prepared by DINCH is bigger than that of plastisols prepared by ATBC.

Rheological and Textural Characteristics of Date Paste

The rheological properties of two commercial date pastes were investigated in the temperature range of 20–70°C. From typical flow behavior curves, it was observed that date pastes exhibited pseudoplastic behavior. The shear stress-shear rate data were fitted using six common rheological models. The Casson model best described the experimental data at all temperatures. The Arrhenius model described successfully the temperature dependence of apparent viscosity of date pastes (R2 > 0.99) with an Ea value in the range of 25,392.6–25,485.7 kJ/kmol. The textural attributes measured were: hardness, springiness, gumminess, cohesiveness, chewiness, and adhesiveness for the texture profile analysis test, and firmness, adhesive force, mean load, and total positive area for the Ottawa test. There was a significant difference in textural attributes between two varieties of date paste studied. Texture profile analysis results showed that all parameters obtained for black date pastes were higher than golden date pastes except for springiness and cohesiveness. However, the Ottawa results showed that golden date pastes were firmer and less adhesive than black date pastes.

A consistent dimensional analysis of gas–liquid mass transfer in an aerated stirred tank containing purely viscous fluids with shear-thinning properties

This paper deals with gas–liquid mass transfer in an aerated stirred tank containing Newtonian or shear-thinning fluids. The aim is to demonstrate that, for a given mixing system, an unique dimensionless correlation gathering all the mass transfer rates (150 kla measurements) can be obtained if and only if the variability of the rheological material parameters is correctly considered when implementing the theory of similarity. More particularly, it is clearly illustrated that a too gross simplification in the relevant list of the parameters characterizing the dependence of apparent viscosity with shear rates leads to pitfalls when building the π-space set. This is then a striking example showing that a robust predictive correlation can be established when the non-constancy of fluid physical properties ceases to be neglected.

Terpolymers as Flow Improvers for Mexican Crude Oils

A series of copolymers derived from styrene (S), n-butyl acrylate (BuA), and vinyl acetate (VA) monomers were prepared by emulsion polymerization to improve some physical properties of Mexican crude oils (MCOs). Once obtained, the copolymers were characterized by Fourier transform infrared (FTIR) spectroscopy, size-exclusion chromatography (SEC), and thermogravimetric analysis (TGA). Later, they were dissolved in toluene and were added to both light and heavy MCOs; the pour point temperature and apparent viscosity of these mixtures were carefully evaluated. Results indicate that styrene and vinyl acetate (SVA) copolymers show a good pour point depressant performance for both types of crude oils. The apparent viscosity dependence on temperature for light and heavy crude oils, mixed with copolymers, was also established. It was observed that, in general, the addition of copolymers decreases the apparent viscosity of both light and heavy crude oils above 35 °C.

Effect of hydroxypropylation on physical and rheological properties of sweet potato starch

Sweet potato starches (SPS) were hydroxypropylated to evaluate the effect of molar substitution (MS, 0.042–0.153) on the rheological properties, thermal properties, freeze-thaw stability, paste clarity, and gel strength of hydroxypropylated sweet potato starches (HPSPS). The swelling power and solubility values of HPSPS were higher than those of native sweet potato starch (SPS) and increased with an increase in MS. The transition temperatures ( T o, T p, and T c), and enthalpy (Δ H) of gelatinization of HPSPS were lower than those of native SPS, and significantly decreased with an increase in MS.Rheological properties of HPSPS pastes were measured under the conditions of steady and dynamic shear. Their consistency index (K), apparent viscosity ( η a,100), Casson yield stress ( σ oc), complex viscosity ( η*), and dynamic moduli ( G′ and G″) values decreased with an increase in MS, while their flow behavior index ( n) and tan δ (ratio of G″/ G′) values increased. The dependence of apparent viscosity on temperature followed the Arrhenius model for all samples. The paste clarity of HPSPS paste was more pronounced with increasing MS of hydroxypropyl groups. The HPSPS gels showed lower gel strength and also better freeze-thaw stability with a significant decrease in syneresis (g/100 g) compared to native SPS.

Rheological and Ultrastructural Properties and Particle Size Distribution of Soymilk as Affected by Processing Methods

Soymilk was prepared from boiled and unboiled comminuted suspensions of dehulled soybean and water using pressurized homogenization (one pass and two pass). Particle size showed significant differences between soymilks homogenized by one pass and two pass. Apparent viscosities and total solid contents showed significant differences between boiled and unboiled treatments. Soymilks exhibited pseudoplastic and thixotropic behavior and Arrhenius model was fitted to express temperature dependence of apparent viscosity. Microscopic images showed hydrated, separated, uniformly distributed, and homogeneous particles in boiled two-pass soymilk as they were disrupted easily and it was selected as the best treatment for processing soymilk containing all of the soybean solids.

Characterization of the Dextran Produced by Leuconostoc mesenteroides from Date Fruit Extract

In the present study, the production of dextran from date extract and sucrose as carbon sources by the bacterium Leuconostoc mesenteroides NRRL B512 (f) was investigated. In comparison to blue dextran (Mw≈2000 Da), dextran molecular weight was reduced (Mw2000 KDa). Flow behavior indices of dextran solutions from date extracts were investigated and rheological parameters were evaluated at concentrations of 1.5, 2.5, 5, together with 10% total solids at 25˚C using a Brookfield rotational viscometer as well as a cone and plate geometry. The experimental results followed the power law model for the best fit and the values of flow behavior index (n) were less than unity (0.49 .93) at all concentrations, revealing the shear thinning nature of the produced dextran. Furthermore, dependence of apparent viscosity on concentration was confirmed using the power law model.

Copolymers as Flow Improvers for Mexican Crude Oils

A series of copolymers derived from styrene (S), n-butyl acrylate (BuA), and vinyl acetate (VA) monomers were prepared by emulsion polymerization to improve some physical properties of Mexican crude oils (MCOs). Once obtained, the copolymers were characterized by Fourier transform infrared (FTIR) spectroscopy, size-exclusion chromatography (SEC), and thermogravimetric analysis (TGA). Later, they were dissolved in toluene and were added to both light and heavy MCOs; the pour point temperature and apparent viscosity of these mixtures were carefully evaluated. Results indicate that styrene and vinyl acetate (SVA) copolymers show a good pour point depressant performance for both types of crude oils. The apparent viscosity dependence on temperature for light and heavy crude oils, mixed with copolymers, was also established. It was observed that, in general, the addition of copolymers decreases the apparent viscosity of both light and heavy crude oils above 35 °C.

RHEOLOGICAL PROPERTIES OF CORIANDER AND MINT LEAF PUREE

ABSTRACT Rheological behavior of coriander and mint leaf puree was determined at temperatures of 30 to 80C. Applicability of various rheological models available in the literature was evaluated. The Herschel–Bulkley model provided a good description of the flow behavior of coriander and mint leaf puree over the temperature range of 30–80C. The Arrhenius model successfully described the effect of temperature on consistency index of coriander and mint puree. The temperature dependence of apparent viscosity of mint puree however did not obey the Arrhenius model. The activation energy of flow for coriander and mint puree was 23.99 and 32.62 kJ/mol, respectively.PRACTICAL APPLICATIONSFlow properties of foods are determined for a number of purposes, such as quality control, understanding the structure, process engineering applications and correlation with sensory evaluation (Cepeda et al. 2002; Nindo et al. 2005). Knowledge of the rheology of suspensions contributes to a better understanding of the underlying mechanisms of momentum and heat transfer process (Telis‐Romero et al. 1999; Nindo et al. 2005). Rheological properties are also important for the design of related processing systems, including filling in bottles/cans and appropriate piping arrangements (Steffe 1992; Bhattacharya 1999). Krokida et al. (2001) recently assembled additional data on rheological properties of fruit and vegetable puree. Limited information is available in the literature on the rheological characteristics of herb purees. Herbal purees vary widely in their rheological characteristics and it is necessary to investigate each product separately. Results of this study would be useful in the quality control and design of processing equipment for processing coriander‐ and mint‐based products.

Comparison of Rheological Behaviour of Salad Sauces

Seventeen commercial salad sauces, made by different manufacturers, were studied to examine their rheological properties. Rheological studies include determination of the following: (a) flow curves with a controlled shear rate or shear stress, and (b) curves showing the time and temperature dependence of apparent viscosity. Apparent viscosity was correlated using the power-law model. The flow behaviour index, n, and the consistency index, K, were calculated and their variation with the temperature (between 20 and 40°C) was studied. Their values varied between 0.19 and 0.51, for n, and between 2.39 and 60.5, for K.

Kinetic Study of Thermal Z to E Isomerization Reactions of Azobenzene and 4‐Dimethylamino‐4′‐nitroazobenzene in Ionic Liquids [1‐R‐3‐Methylimidazolium Bis(trifluoromethylsulfonyl)imide with R=Butyl, Pentyl, and Hexyl

Thermal Z to E isomerization reactions of azobenzene and 4-dimethylamino-4'-nitroazobenzene were examined in three ionic liquids of general formula 1-R-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (R = butyl, pentyl, and hexyl). The first-order rate constants and activation energies for the reactions of azobenzene measured in these ionic liquids were consistent with those measured in ordinary organic solvents, which indicated that the slow isomerization through the inversion mechanism with a nonpolar transition state was little influenced by the solvent properties, such as the viscosity and dielectric constant, of ionic liquids. On the other hand, the rate constants and the corresponding frequency factors of the Arrhenius plot were significantly reduced for the isomerization of 4-dimethylamino-4'-nitroazobenzene in ionic liquids compared with those for the isomerization in ordinary organic molecular solvents with similar dielectric properties. Although these ionic liquids are viscous, the apparent viscosity dependence of the rate constant could not be explained either by the Kramers-Grote-Hynes model or by the Agmon-Hopfield model for solution reactions. It is proposed that the positive and the negative charge centers of a highly polar rotational transition state are stabilized by the surrounding anions and cations, respectively, and that the ions must be rearranged so as to form highly ordered solvation shells around the charge centers of the reactant in the transition state. This requirement for the orderly solvation in the transition state results in unusually small frequency factors of 10(4)-10(7) s(-1).