Infinite Shear Viscosity Research Articles

Analysis of compressible bubbly flows. Part I: construction of a microscopic model

In this note, we introduce a microscopic model for the motion of gas bubbles in a viscous fluid. By interpreting a bubble as a compressible fluid with infinite shear viscosity, we derive a pde/ode system coupling the density/velocity/pressure in the surrounding fluid with the linear/angular velocities and radii of the bubbles. We provide a 1D analogue of the system and construct an existence theory for this simplified system in a natural regularity framework. The second part of the paper is a preparatory work for the derivation of an averaged or macroscopic model.

Estimation of Drag Reduction by Polymer Additives at High Reynolds Numbers Using Rheological Measurements

In industrial applications such as hydraulic water fracking, polymers are added at dilute concentrations to the flow causing significant drag reduction (DR) and leading to a massive reduction to pump energy cost. In recent years, an alternative approach that is based on rotational flow has shown capabilities of measuring DR based purely on rheological testing. Nonetheless, there are some limiting assumptions in this approach that can lead to inaccurate interpretation of the data, especially for non-Newtonian polymer solutions, where the Reynolds number (Re) is evaluated at the infinite-shear or solvent viscosities. However, it is well known that the apparent viscosity of the polymer solutions is higher than that of a solvent at a stable region and lower than infinite shear viscosity at an unstable one. In this study, we propose a theoretical form of the DR expression that is based on the Re, which is estimated at the apparent local viscosity measure. The work establishes a promising approach for screening DR agents using rheological measurements. Moreover, the study presents new theoretical findings and analyses for estimating DR and extrapolating the results to high Re. Two polymer solutions of xanthan gum (XG) and partially hydrolyzed polyacrylamide (HPAM) in distilled water are tested at concentrations between 5 and 150 ppm using a concentric double-gap cylinder. The proposed approach is found to be more consistent with the theory of linear flow (i.e., flow loop), where the DR in the stable region is found to be identically zero. The transition from stable to unstable regions is also consistent with the existing linear flow theory. This enhances the role of rheological testing for DR measurements and DR agent screening, which provides a platform for the application of simple and cost-effective rheometry in the DR industry.

Steady shear rheological properties, microstructure and stability of water in water emulsions made with basil seed gum and waxy corn starch or high pressure-treated waxy corn starch

The water in water (W/W) emulsions were prepared by mixing basil seed gum (BSG) with waxy corn starch (WCS) or high pressure-treated waxy corn starch (HWCS) at different concentrations. Increasing the concentration of WCS or HWCS increased the zeta potential, consistency index, infinite shear viscosity, and apparent viscosity, while it decreased the Z-average droplet size, polydispersity index, separation index, and flow behavior index of the W/W emulsions. After increasing the concentration of WCS and HWCS, the micrographs captured by an optical microscope indicated that the number of follicular droplets increased more than individual droplets. However, coalescence did not occur due to electrostatic repulsion. When the concentration of WCS and HWCS was increased from 0.5 to 2 wt% (at a constant concentration of 0.25 wt% and 0.2 wt% of BSG, respectively), the consistency index of the emulsions was increased significantly (p < 0.05) from 0.109 to 0.436 Pa. sn and from 0.032 to 0.743 Pa. sn, respectively. The results simply revealed the capability of 0.2 wt% BSG+ 0.5, 1, or 2 wt% HWCS and 0.25 wt% BSG+ 0.5, 1, or 2 wt% WCS for being utilized as stable W/W emulsions; these emulsions were stable for at least a week.

Infinite shear rate aspect of the cross-nanofluid over a cylindrical channel with activation energy and inclined magnetic dipole effects

The posture of fluid flow at a high or low shear rate is characterized by the infinite shear viscosity concept based on the Cross-fluid (CF). This dynamical system has some characteristics to examine the extreme levels of the fluid along with the effects of inclined magnetic dipole mechanics. The current research is examines the infinite shear rate based on the CF past over the cylindrical channel. The velocity through an inclined magnetic field, based on the cylindrical geometry and the activation energy, is provided using mass transport along with the chemical reactions. Moreover, the thermophoresis effects, Brownian motion based on the nanoparticles, and binary chemical procedures are also provided in this study. The CF model is provided through the tensor of Cauchy stress along with the partial differential equations (PDEs). Similarity transformations have been used to convert the PDEs into ordinary differential equations. The numerical performances of the obtained system have been obtained by using the bvp4c method.

Evaluation of L-ascorbic acid as a green low dosage hydrate inhibitor in water-based drilling fluid for the drilling of gas hydrate reservoirs

Hydrate plug formation in the drilling fluid flow line is a significant issue in the oil and gas industry. Green hydrate inhibitors have recently gained much interest in flow assurance problems as they are being used as alternatives for existing hydrate inhibitors. The present study described that L-ascorbic acid (LA), a natural organic compound, has been identified as a Low Dosage Hydrate Inhibitor and has exhibited better results than Polyvinylcaprolactum (PVCap) and Polyvinylpyrrolidone (PVP). The temperature-augmented visual method and a self-fabricated set-up have been used to determine the first hydrate crystal formation in the tetrahydrofuran (THF)-water hydrate system. LA has shown a better inhibition effect in terms of induction time (i.e., >1440 min) than PVCap (119.67–180.67 min) and PVP (85.33–240.67 min). Carboxymethyl cellulose (CMC), polyanionic cellulose (PAC), xanthan gum (XG), and potassium chloride (KCl) are mixed with water to make the water-based drilling fluids used in this study. The R2 values showed a good agreement with the Herschel-Bulkley Model (R2 ranges from 0.993 to 0.999 for 0.5 w/v% PVCap and 0.1 w/v% PVP-containing fluids) than Bingham Plastic Model (R2 ranges from 0.836 to 0.952 for 0.1 w/v% PVP and base fluids). The MPE values are less for Herschel-Bulkley Model (From 1.418 to 6.015 for 0.5 w/v% PVCap and 0.1 w/v% PVP) than for Bingham Plastic (From 9.985 to 29.718 for 1.0 w/v% PVP and 0.1 w/v% PVP). Cross Model is also used to determine the zero and infinite shear viscosities for the formulated fluid system, which showed the viscosities are in the permissible range. These observations suggest that L-ascorbic acid (LA) may be an effective hydrate inhibitor in drilling fluids.

Activation Energy and Inclination Magnetic Dipole Influences on Carreau Nanofluid Flowing via Cylindrical Channel with an Infinite Shearing Rate

Background: The infinite shear viscosity model of Carreau fluid characterizes the attitude of fluid flow at a very high/very low shear rate. This model has the capacity for interpretation of fluid at both extreme levels, and an inclined magnetic dipole in fluid mechanics has its valuable applications such as magnetic drug engineering, cold treatments to destroy tumors, drug targeting, bio preservation, cryosurgery, astrophysics, reaction kinetics, geophysics, machinery efficiency, sensors, material selection and cosmology. Novelty: This study investigates and interprets the infinite shear rate of Carreau nanofluid over the geometry of a cylindrical channel. The velocity is assumed to be investigated through imposing an inclined magnetic field onto cylindrical geometry. Activation energy is utilized because it helps with chemical reactions and mass transport. Furthermore, the effects of thermophoresis, the binary chemical process and the Brownian movement of nanoparticles are included in this attempt. Formulation: The mathematics of the assumed Carreau model is derived from Cauchy stress tensor, and partial differential equations (PDEs) are obtained. Similarity transformation variables converted these PDEs into a system of ordinary differential equations (ODEs). Passing this system under the bvp4c scheme, we reached at numerical results of this research attempt. Findings: Graphical debate and statistical analysis are launched on the basis of the obtained computed numerical results. The infinite shear rate aspect of Carreau nanofluid gives a lower velocity. The inclined magnetic dipole effect shows a lower velocity but high energy. A positive variation in activation energy amplifies the concentration field.

Polymer-Induced Drag Reduction in Dilute Newtonian and Semi-Dilute Non-Newtonian Fluids: An Assessment of the Double-Gap Concentric Cylinder Method.

Polymer-induced drag reduction (DR) in fluids was studied using a rotational rheometer with double-gap concentric cylinder geometry. Although both polymers (polyacrylamide (PAM) and 2-acrylamido-2-methylpropane sulfonic acid (SPAM)) had molecular weights of several MDa, the contrasting polymer charge, nonionic and anionic, led to different polymer overlap concentrations (c*), PAM ≫ SPAM, and fluid rheology, with PAM fluids mostly Newtonian and SPAM fluids non-Newtonian (shear-thinning). Based on these differences, it was important to account for the infinite shear viscosity and normalize the polymer concentration by the intrinsic concentration (cint) so that the DR performance of the two polymer fluids could be accurately compared. Both polymers induced DR, and the maximum DR by SPAM (DR% = 28) was slightly higher than that by PAM (DR% = 22) when Rep ∼ 1700. For PAM, the loss of DR with time diminished at higher polymer concentrations (≥100 ppm, at Rep = 3149) but was found to be sensitive to high Rep, with polymer chain scission the likely cause of the reduced performance. For the semi-dilute SPAM fluids, the shear stability contrasted that of PAM, showing negligible dependence on the polymer concentration and Rep. The apparent rapid loss of DR was predominantly attributed to a time-dependent effect and not polymer degradation. In pipe flow, the maximum DR for SPAM was higher than that measured by rheometry and was attributed to differences in the flow conditions. However, changes in the normalized DR/c with polymer concentration were found to be consistent between the two flow geometries. Furthermore, the high fluid stresses in pipe flow (at high Rep) led to drag reduction losses consistent with PAM, as the time-dependent effect was not seen.

Rheological characterization of cemented paste backfills containing superabsorbent polymers (SAPs)

The addition of superabsorbent polymers (SAP) to cemented paste backfill (CPB) made from tailings slurries may offer a good alternative to the dewatering components of the conventional CPB production owing to their high-water absorption and retention capacities. Therefore, an experimental program was implemented to characterize the rheological behavior of CPB incorporating an SAP. Two types of binder comprising a general use Portland cement (GU) and a blended binder (GUSL) consisting of 80% ground granulated blast furnace slag (GGBFS) and 20% GU were used. Two different binder proportions, Bw (=100 × Mbinder/Mdry-tailings) of 4.5 and 7% were tested. An SAP dosage (ratio of the dry mass of SAP to the volume of the tailings slurry) of 30 and 34 kg/m3 was assessed in this study. Results showed that the SAP addition distinctly reduced the yield stress (τ0) and the infinite shear viscosity (μ∝) and increased the small cone (H = 150 mm) slump height (s) of such mixtures over time. Moreover, The SAP-thickened tailings CPB (SAP-TT CPB) showed a severe shear-thinning behavior marked by a negative flow index (n < 0) and moderate to extremely low yield stress (τ0 in the range 21–78 Pa), while the corresponding reference CPB without SAP added (Ref) exhibited a normal shear-thinning behavior with moderate to slightly high yield stress (τ0 in the range 76–206 Pa).

Buffered λ-DNA solutions at high shear rates

We study buffered aqueous solutions of deoxyribonucleic acid isolated from bacteriophage lambda (λ-DNA) at shear rates up to 105 s−1. The shear rates are accessed with a narrow-gap rheometer at gap widths down to 20 μm. At lower shear rates, our data merge with the literature values. At high shear rates, the viscosity levels off into an infinite-shear viscosity plateau. Hence, the viscosity functions of buffered aqueous DNA solutions are now available for the entire shear-rate range from the first Newtonian plateau to that of infinite-shear viscosity. The latter hardly differs from the solvent viscosity. For the normal-stress differences, we observe a power-law dependence on the shear rate close to previous findings up to shear rates of about 104 s−1. Beyond this shear-rate range, we observe a stepwise change with the shear rate. By means of agarose gel electrophoresis, we confirm that the λ-DNA is not fragmented during our rheometric study at high shear rates. Yet, at the highest shear rates studied, shear-induced changes in the DNA to structures not being able to travel through the gel appear.

Temperature-Dependent Rheological Behaviors of Binary Eutectic Mixtures of Sugar Alcohols for Latent Heat Storage: A Comparative Study with Pure Sugar Alcohols

The temperature-dependent rheological behaviors of five selected binary eutectic mixture sugar alcohols, with great potential for latent heat storage in the range of 353.15 K to 523.15 K, were investigated. It was found that the rheological behaviors of the mixture sugar alcohols depend on those of the pure compounds as well as their molar ratios. The two mixtures of xylitol (75 mol%)+erythritol and erythritol (84 mol%)+d-mannitol behave like pseudoplastic fluids with typical non-Newtonian shear-thinning behaviors, as indicated by the power law index of 0.99 (<1). The mixture of d-mannitol (70 mol%)+d-dulcitol is a nonlinear Bingham fluid, exhibiting a slight yield stress (0.001 Pa to 0.01 Pa) at low shear rates. The rest two mixtures containing the cyclic-structured inositol behave like Herschel-Bulkley fluids. The infinite shear viscosities of the eutectic mixtures over the entire temperature range appear to be higher than those of their respective pure compounds, except for inositol. The mixture of xylitol (75 mol%)+erythritol at its melting point shows higher dynamic viscosity of about 0.546 Pa·s than the values of about 0.396 Pa·s and 0.035 Pa·s for xylitol and erythritol, respectively. In addition, the activation energies of viscous flow of the mixtures, as determined by fitting the dynamic viscosity-temperature curves using the Arrhenius model, also exhibit higher values than those of their pure compounds. The activation energy of viscous flow of the mixture xylitol (75 mol%)+erythritol was determined to be about 92 400 J/mol in the supercooled liquid state, while the supercooled liquid xylitol and erythritol have much lower values of 83 500 J/mol and 51 900 J/mol, respectively. Both the increased dynamic viscosities and activation energies of viscous flow can result in deteriorated crystallization performance during latent heat retrieval.

Rheology by Design: A Regulatory Tutorial for Analytical Method Validation.

The increasing demand for product and process understanding as an active pursuit in the quality guideline Q8 and, more recently, on the draft guideline on quality and equivalence of topical products, has unveiled the tremendous potential of rheology methods as a tool for microstructure characterization of topical semisolid dosage forms. Accordingly, procedure standardization is a dire need. This work aimed at developing and validating a methodology tutorial for rheology analysis. A 1% hydrocortisone cream was used as model cream formulation. Through a risk assessment analysis, the impact of selected critical method variables (geometry, temperature and application mode) was estimated in a broad range of rheological critical analytical attributes—zero-shear viscosity, upper-shear thinning viscosity, lower-shear thinning viscosity, infinite-shear viscosity, rotational yield point, thixotropic relative area, linear viscoelastic region, oscillatory yield point, storage modulus, loss modulus, and loss tangent. The proposed validation of the approach included the rheometer qualification, followed by the validation of numerous operational critical parameters regarding a rheology profile acquisition. The thixotropic relative area, oscillatory yield point, flow point and viscosity related endpoints proved to be highly sensitive and discriminatory parameters. This rationale provided a standard framework for the development of a reliable and robust rheology profile acquisition.

Effect of polymer solutions on the propagation and structure of freely translating vortex rings

We experimentally study the propagation of vortex rings in aqueous solutions of polyethylene oxide (PEO400) and hydrolysed polyacrylamide (PAMH25). We study the canonical vortex ring as a caricature problem to the phenomenon of turbulent polymer drag reduction. PAMH25 has a similar infinite shear viscosity, ten times the zero shear viscosity and a thousand times the relaxation time of PEO400. We study the vortex rings generated by the trapezoidal motion of a piston-cylinder mechanism using PIV and PLIF at constant impulse. We see that PAMH25 drastically affects the propagation properties and the structure of the vortex ring, while PEO400 shows a behaviour similar to water. We conclude that PAMH25 retards the roll-up process of the ring, due to both the large range of plateau viscosities and large relaxation time. We surmise that the behaviour of the vortex ring observed might be used to unravel the mechanism of polymer drag reduction.

Experimental investigation of vortex ring evolution in polymer solutions

Results on formation and propagation of vortex rings, in water and different concentration of the turbulent-drag reducing polymer (PAMH - hydrolyzed polyacrylamide) solutions are presented. Adding PAMH changes solvent viscosity, elasticity and relaxation time. Vortex-ring properties such as ring-velocity, circulation, enstrophy, kinetic energy and vorticity are measured using Particle Image Velocimetry (PIV). We show that, at constant impulse, vortex ring properties in PAMH solution deviate from that in Newtonian-fluid, water. We further perform experiments in water by matching the limiting Reynolds numbers of the PAMH solution corresponding to zero-shear and infinite-shear viscosities. While the circulation of PAMH solutions lie between the circulation of the two limiting Reynolds numbers of water experiments, however, enstrophy and peak vorticity do not follow this trend. We attribute the deviation of PAMH-rings to the modification of vorticity distribution. PLIF experiments show the phenomenon of ring-reversal, we attribute this to the elastic properties of the polymer-solution.

Bioactive amorphous magnesium phosphate-polyetheretherketone composite filaments for 3D printing

ObjectiveThe aim of this study was to develop bioactive and osseointegrable polyetheretherketone (PEEK)-based composite filaments melt-blended with novel amorphous magnesium phosphate (AMP) particles for 3D printing of dental and orthopedic implants. Materials and methodsA series of materials and biological analyses of AMP-PEEK were performed. Thermal stability, thermogravimetric and differential scanning calorimetry curves of as-synthesized AMP were measured. Complex viscosity, elastic modulus and viscous modulus were determined using a rotational rheometer. In vitro bioactivity was analyzed using SBF immersion method. SEM, EDS and XRD were used to study the apatite-forming ability of the AMP-PEEK filaments. Mouse pre-osteoblasts (MC3T3-E1) were cultured and analyzed for cell viability, proliferation and gene expression. For in vivo analyses, bare PEEK was used as the control and 15AMP-PEEK was chosen based on its in vitro cell-related results. After 4 or 12 weeks, animals were euthanized, and the femurs were collected for micro-computed tomography (μ-CT) and histology. ResultsThe collected findings confirmed the homogeneous dispersion of AMP particles within the PEEK matrix with no phase degradation. Rheological studies demonstrated that AMP-PEEK composites are good candidates for 3D printing by exhibiting high zero-shear and low infinite-shear viscosities. In vitro results revealed enhanced bioactivity and superior pre-osteoblast cell function in the case of AMP-PEEK composites as compared to bare PEEK. In vivo analyses further corroborated the enhanced osseointegration capacity for AMP-PEEK implants. SignificanceCollectively, the present investigation demonstrated that AMP-PEEK composite filaments can serve as feedstock for 3D printing of orthopedic and dental implants due to enhanced bioactivity and osseointegration capacity.

Change in internal energy of Carreau fluid flow along with Ohmic heating: A Von Karman application

This article examine the impact of internal energy change in steady, Carreau incompressible electrically conducting fluid flow due to a porous Von Karman problem under the effects of transverse magnetic field and Ohmic heating. The nonlinearities generated by the rheological fluid model declines the numerical convergence of outcome results, that is why infinite shear viscosity is assumed to be zero. The basic mathematical model (system of PDEs) is converted into nonlinear ODEs by applying Von Karman similarity transformations. Numerical solutions of the resultant equations are achieved by utilizing (fifth order Runge–Kutta–Fehlberg method) along with shooting technique. Detailed variations of radial and tangential components of the velocity as function of Ha number, power law index, Reynold number and We number have been computed for further analysis. Phenomena of heat and mass transfer depends on thermal-diffusion and diffusion-thermo aspects. So, Soret and Dufour effects are also added in this analysis.

Unidirectional large-amplitude oscillatory shear flow of human blood

Blood is a non-Newtonian suspension of red and white cells, platelets, fibrinogen, and cholesterols in Newtonian plasma. To assess its non-Newtonian behaviors, this work considers a newly proposed blood test, unidirectional large-amplitude oscillatory shear flow (udLAOS). In the laboratory, we generate this experiment by superposing LAOS onto steady shear flow in such a way that the shear rate never changes sign. It is thus intended to best represent the unidirectional pulsatile flow in veins and arteries. To model human blood, we consider the simplest model that can predict infinite-shear viscosity, the corotational Jeffreys fluid. We arrive at an exact analytical expression for the shear stress response of this model fluid. We discover fractional harmonics comprising the transient part of the shear stress response and both integer and fractional harmonics, the alternant part. By fractional, we mean that these occur at frequencies other than integer multiples of the superposed oscillation frequency. We generalize the corotational Jeffreys fluid to multimode to best represent three blood samples from three healthy but different donors. To further improve our model predictions, we consider the multimode Oldroyd 8-constant framework, which contains the corotational Jeffreys fluid as a special case. In other words, by advancing from the multimode corotational Jeffreys fluid to the multimode Oldroyd 8-constant framework, five more model parameters are added, yielding better predictions. We find that the multimode corotational Jeffreys fluid adequately describes the steady shear viscosity functions measured for three different healthy donors. We further find that adding two more specific nonlinear constants to the multimode corotational Jeffreys fluid also adequately describes the behaviors of these same bloods in udLAOS. This new Oldroyd 5-constant model may find usefulness in monitoring health through udLAOS.

The Role of Grease Composition and Rheology in Elastohydrodynamic Lubrication

Grease lubrication is inherently complicated due to its non-Newtonian flow dynamics. The flow behavior of grease is difficult to determine under tribological shear rates as these shear rates are often extremely high, and therefore, are not accessible on a regular rheometer. In this work, we demonstrate the use of shear rate-concentration superposition method to extrapolate the data measured with a rheometer to tribologically relevant shear rates. This method is similar to the other superposition methods routinely employed by rheologists for predicting flow behavior beyond the measurement range of rheometer. In this method, a data master curve, which extends over a broad range of shear rates, is constructed by superposing individual flow curves for greases with different thickener concentrations. The master curve is utilized to determine infinite shear viscosity of grease which is then used for the film thickness estimation. Furthermore, the grease samples are tribologically tested using a four-ball tester to identify the individual and interactive roles of the thickener type, concentration and base oil in lubrication behavior. A change in thickener concentration or type influences frictional torque and wear scar size through modification in infinite shear viscosity and structural stability of grease. The SEM images show deposition of thickener particles on the contact surface, which also apparently affect friction and wear during the test. The lubrication performance is strongly influenced by base oil, which points towards the importance of its role in dictating flow resistance and film-forming behavior of grease inside elastohydrodynamic contact.

Whey protein stabilized nanoemulsion: A potential delivery system for ginsenoside Rg3 whey protein stabilized nanoemulsion: Potential Rg3 delivery system

In the current research, we systematically investigated the physicochemical stability of the nanoemulsions that were formulated with 90% (v/v) whey protein isolate (WPI) aqueous phase and 10% (v/v) medium chain triglyceride oil phase at neutral pH using high intensity ultrasonication. We measured the physicochemical properties of nanoemulsions stabilized by WPI at different concentrations, including particle size, zeta potential, turbidity, centrifugal stability, and rheological behavior. Besides, we also evaluated the influence of processing conditions (ionic strength, freeze-thaw cycle and thermal treatment) on the nanoemulsion stability. The particle size of WPI nanoemulsions increased by approximately 5% at 25 °C and 8% at 37 °C after 7 weeks’ storage, while the particle size and zeta potential of the nanoemulsions at 4 °C were changed. The 1% WPI stabilized nanoemulsion was very sensitive to Na+ (0.1–0.5 mol/l) and freeze-thaw treatment (3 cycles) with significant increase in particle size and decrease in the absolute value of zeta potential. The turbidity of nanoemulsions decreased by over 50% after freeze-thaw cycles, especially the 1% WPI stabilized nanoemulsion. All samples were still stable under thermal conditions. Among them, the 5% WPI stabilized nanoemulsion showed the best ionic, freeze-thaw, and thermal stability. All tested nanoemulsions showed typical shear-thinning behavior, and the infinite shear viscosity of 5% WPI stabilized nanoemulsions was highest. In conclusion, the 5% WPI stabilized nanoemulsion has the best physicochemical stability under different processing conditions during storage, which has high potential in use as a delivery system for bioactive substances like ginsenoside Rg3 in food technology.

Rheological behaviors of sugar alcohols for low-to-medium temperature latent heat storage: Effects of temperature in both the molten and supercooled liquid states

As potential candidates of solid−liquid phase change materials (PCM) for latent heat storage in the low-to-medium temperature range (80–250 °C), the temperature-dependent rheological behaviors of five select sugar alcohols were characterized over a wide range of shear rates from 10−3 s−1 to 104 s−1. It was found that the four linear-structured sugar alcohols, i.e., xylitol, erythritol, d-mannitol, and d-dulcitol, are Newtonian fluids above their respective critical shear rates, in both the molten and supercooled liquid states, and that they exhibit typical shear thinning behaviors below the critical shear rates. In particular, d-mannitol and d-dulcitol, with relatively higher melting points, behave like Herschel-Bulkley fluids, which experience slight yield under small yield stresses (0.0001–0.0099 Pa s and 0.0078–0.0528 Pa s for d-mannitol and d-dulcitol, respectively). Inositol, the only cyclic-structured sugar alcohol with the highest melting point (497.65 K), also behaves like a Herschel-Bulkley fluid in both the molten and supercooled liquid states. The dynamic viscosity curves of inositol were found to agree with the Cross model, leading to determination on its zero shear and infinite shear viscosities. An Arrhenius-type dynamic viscosity-temperature curve was observed for inositol over the entire temperature range at the highest shear rate of 104 s−1.

Infinite-shear viscosity plateau of salt-free aqueous xanthan solutions

We study aqueous xanthan solutions at shear rates up to about 105 s−1. At these shear rates, the salt-free solutions show an infinite-shear viscosity plateau. Depending on the xanthan concentration, we find two different regimes with scaling laws well known for the zero-shear viscosity of dilute and semidilute solutions: The crossover concentration is considerably higher than in the first Newtonian branch, which can be related to the orientation of the polyelectrolytes. In the second regime, the normal stress differences increase with an exponent of about 1, indicating that the polymer solution behaves like nematic liquid crystals or rigid fiber suspensions. In the first regime, the exponent is smaller suggesting that the polyelectrolytes behave more flexible.