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Background: Synovial fluid (SF) is often used for diagnostic and research purposes as it reflects the local inflammatory environment. Owing to its complex composition, especially the presence of hyaluronic acid, SF is usually viscous and non-homogeneous. The presence of high-molar-mass hyaluronan in this fluid gives it the required viscosity for its function as a lubricant. Viscosity is the greatest major hydraulic attribute of the SF in articular cartilage. Methods: Empirical modeling of previously published results was performed. In this study, we explored the flow of a non-Newtonian fluid that could be used to model the SF flow. Analyzing the flow in a simple geometry can help explain the model's efficacy and assess the SF models. By employing some viscosity data reported elsewhere, we summarized the dynamic viscosity values of normal human SF of the knee joints in terms of time after injecting hyaluronidase (HYAL) at 25°C. The suggested quadratic behavior was obtained through extrapolation. For accurate diagnosis or prediction, the comparison between three specific parameters (ai, t0, and ln η0) was made for normal and pathological cases under the same experimental conditions for treatment by addition of HYAL and for investigation of the rheological properties. A new model on the variation of viscosity on the SF of knee joints with time after injection of HYAL with respect to normal and postmortem samples at different velocity gradients was proposed using data previously reported elsewhere. Results: The rheological behavior of SF changes progressively over time from non-Newtonian to a Newtonian profile, where the viscosity has a limiting constant value (η0) independent of the gradient velocity at a unique characteristic time (t0 ≈ 8.5 h). The proposed three-parameter model with physical meaning offers insights into future pathological cases. The outcomes of this work are expected to offer new perspectives for diagnosis, criteria, and prediction of pathological case types through comparisons with new parameter values treated under the same experimental conditions as HYAL injection. This study also highlights the importance of HYAL treatment for better intra-assay precision. [ABSTRACT FROM AUTHOR]

BackgroundSynovial fluid (SF) is often used for diagnostic and research purposes as it reflects the local inflammatory environment. Owing to its complex composition, especially the presence of hyaluronic acid, SF is usually viscous and non-homogeneous. The presence of high-molar-mass hyaluronan in this fluid gives it the required viscosity for its function as a lubricant. Viscosity is the greatest major hydraulic attribute of the SF in articular cartilage.MethodsEmpirical modeling of previously published results was performed. In this study, we explored the flow of a non-Newtonian fluid that could be used to model the SF flow. Analyzing the flow in a simple geometry can help explain the model’s efficacy and assess the SF models. By employing some viscosity data reported elsewhere, we summarized the dynamic viscosity values of normal human SF of the knee joints in terms of time after injecting hyaluronidase (HYAL) at 25°C. The suggested quadratic behavior was obtained through extrapolation. For accurate diagnosis or prediction, the comparison between three specific parameters (ai, t0, and ln η0) was made for normal and pathological cases under the same experimental conditions for treatment by addition of HYAL and for investigation of the rheological properties. A new model on the variation of viscosity on the SF of knee joints with time after injection of HYAL with respect to normal and postmortem samples at different velocity gradients was proposed using data previously reported elsewhere.ResultsThe rheological behavior of SF changes progressively over time from non-Newtonian to a Newtonian profile, where the viscosity has a limiting constant value (η0) independent of the gradient velocity at a unique characteristic time (t0 ≈ 8.5 h). The proposed three-parameter model with physical meaning offers insights into future pathological cases. The outcomes of this work are expected to offer new perspectives for diagnosis, criteria, and prediction of pathological case types through comparisons with new parameter values treated under the same experimental conditions as HYAL injection. This study also highlights the importance of HYAL treatment for better intra-assay precision.

A study has been made of the flow of a non-Newtonian polymer medium in a plane channel and of heat transfer in it with boundary conditions of the first kind for small Reynolds numbers and a large Péclet number with the Ellis rheological model with a viscosity dependent on the temperature, pressure, and degree of chemical conversion of the medium. Consideration was given to the flow of a high-viscosity medium with chemical reactions leading to an abrupt increase in its viscosity for whose mathematical description the authors used a model that included the kinetic chemical-reaction equation and the energy equation with a dissipative term. Significant influence of various factors on the formation and rate of growth of the solidified wall layer in such flow has been shown. The problem has been solved numerically by the finite-diff erence method according to the iterative scheme. [ABSTRACT FROM AUTHOR]

Abstract This work attempted to conduct an experimental study which demonstrates the effect of the initial concentration of solute on the apparent viscosity of ice slurry in a horizontal circular pipe. The study was conducted on ice slurry based on propylene glycol, varying from 5 to 24% with different ice mass fractions varying from 5 to 25%. During the experiments, the initial concentration of the propylene glycol, ice concentration, and flow rate was modified as parameters. The flow tests were performed on laminar flows. The results of the investigation revealed that the ice slurry behaved like a non-Newtonian fluid, while it sometimes behaved like a Newtonian fluid. The rheological behavior of the ice slurry is reflected by its viscosity. For the shear-thickening behavior, the apparent viscosity increases with increasing the shear rate, and for the shear-thinning behavior, the viscosity decreases with increasing the shear rate, while for the Newtonian behavior, the viscosity remains almost constant. Then it was revealed that the viscosity of the mixture became too high for low shear rates at high ice mass fractions by increasing the concentration of the solute. The power law was used to establish a relationship between the apparent viscosity and the indexes of flow and consistency of ice slurry.

This work attempted to conduct an experimental study which demonstrates the effect of the initial concentration of solute on the apparent viscosity of ice slurry in a horizontal circular pipe. The study was conducted on ice slurry based on propylene glycol, varying from 5 to 24% with different ice mass fractions varying from 5 to 25%. During the experiments, the initial concentration of the propylene glycol, ice concentration, and flow rate was modified as parameters. The flow tests were performed on laminar flows. The results of the investigation revealed that the ice slurry behaved like a non-Newtonian fluid, while it sometimes behaved like a Newtonian fluid. The rheological behavior of the ice slurry is reflected by its viscosity. For the shear-thickening behavior, the apparent viscosity increases with increasing the shear rate, and for the shear-thinning behavior, the viscosity decreases with increasing the shear rate, while for the Newtonian behavior, the viscosity remains almost constant. Then it was revealed that the viscosity of the mixture became too high for low shear rates at high ice mass fractions by increasing the concentration of the solute. The power law was used to establish a relationship between the apparent viscosity and the indexes of flow and consistency of ice slurry. [ABSTRACT FROM AUTHOR]

In this article, we consider the boundary layer two-dimensional Carreau fluid flow induced by a heated inclined flat plate. The flow having variational viscosity of Carreau fluid is considered. The dependence of thermo-physical properties on temperature and concentration is also discussed. Using the Falkner-Skan solution, the governing equations are converted into a system of ordinary differential equations, which have been solved by RK-five integration scheme along with a shooting method. Solutions are calculated for fluid with thermo-physical properties of shear-thinning (viscosity decreases with increasing shear-rate) and thickening (viscosity increases with increasing shear-rate) effects. Physical interpretation and discussion are presented regarding the base flow, temperature and concentration profiles. Boundary layer thickness engages inversely with pressure gradient m , whereas temperature profile shows a significant increase for higher values of ε 1. [ABSTRACT FROM AUTHOR]

Blood is a shear-thinning non-Newtonian fluid in which the viscosity reduces with the shear rate. When simulating arterial flow, it is well established that the non-Newtonian nature is important in the smallest vessels; however, there is no consistent view as to whether it is required in larger arteries, such as the carotid. Here, we investigate the importance of incorporating a non-Newtonian model when applying a plaque deposition model which is based on near-wall local haemodynamic markers: the time-averaged near wall velocity and the ratio of the oscillatory shear index to the wall shear stress. In both cases the plaque deposition was similar between the Newtonian and non-Newtonian simulations, with the observed differences being no more significant than the differences between the selected markers. More significant differences were observed in the haemodynamic properties in the stenosed region, the most significant being that lower levels of near-wall reverse flow were observed for a non-Newtonian fluid. [ABSTRACT FROM AUTHOR]

The poor mixing caused by zinc powder deposition in purification process is a serious problem which can't be avoided in treatment of zinc-containing solid waste. Here, to enhance the purification efficiency of zinc-containing solid waste treatment reactor, two kinds of multi-blade combined stirring systems are compared with single layer four straight-blade and double-layer straight-blade (DFB) stirring systems which are traditionally chosen by industry. This study simulated and explored the flow field characteristics and purification effects of these four kinds of stirred-tank reactor, further proposes the unit ion purification energy (UIPE) as a criterion for purification energy consumption and effect evaluation. The results show that multi-blade combined (MBC) stirring system enhances axial flow by 12.56% in water. Meanwhile it effectively inhibits the growth of isolated mixing region which scope has decreased by 56.25%. In high viscosity Carboxymethylcellulose sodium solution, the fluid axial speed can be increased by up to 1407 times with MBC. MBC can increase the purification rate by 24.79% while the UIPE decreases by 29.45% compared with DFB which is used in industrial purification process. MBC paddle has exhibited a wide range of fluid viscosity applicability and axial velocity improvement effect. The improvement increases collisions between the impurity particles and the zinc powder particles, which increased rate of substitution reactions. The application of MBC solves the purification problem in the process of treating zinc-containing solid waste. [ABSTRACT FROM AUTHOR]

This paper discusses the existence and uniqueness of local strong solution for a class of 1D non-Newtonian fluids with non-Newtonian potential and damping term. Here we allow the initial vacuum and viscosity term to be fully nonlinear. [ABSTRACT FROM AUTHOR]

The rheological behavior of aqueous solutions of polyvinyl alcohol at 4, 6, 8 and 10% by weight has been studied and evaluated at temperatures of 20, 25, 30 and 35 °C, using five non-Newtonian fluid models independent of time: Ferrys, Robertson-Stiff, Williamson, Sisko, and Ellis de Haven. The classical method consists in carrying out regression analysis. Using a comparative procedure of determination coefficients and variances, the model that most appropriately adjusts the experimental data to said model is selected. From the statistical point of view, the Sisko and Robertson-Stiff models present better regression parameters; to better specify the choice of the respective rheological model, a new factor has been proposed in the literature, the viscosity factor (VF), which expresses the relationship between apparent and dynamic viscosity. The analysis of this factor for the five models confirms the greater stability of the Ellis de Haven model in terms of the coefficient of variation of the VF. The value of VF fluctuates between 1 and 2 for all ranges of temperature and concentration experienced for vinyl alcohol solutions. As a consequence of the above, for the choice of the non-Newtonian fluid model associated with the rheology of the aqueous solution of polyvinyl alcohol, it is necessary to analyze the statistical parameters and the VF factor simultaneously. [ABSTRACT FROM AUTHOR]

In this paper, a mathematical model of forward roll for coating a thin viscoplastic fluid onto a moving porous web is developed when the web passes through a small gap between the two rigid rolls. The conservation equations in the light of lubrication approximation theory are non-dimensionalized and solutions for the velocity profile, flow rate, pressure distribution are calculated numerically by using Range-Kutta-Fehlberg's method. It is found that by changing (increasing/decreasing) the material parameters, one can really control the engineering quantities like velocity distribution, flow rate, pressure distribution, and penetration depth The velocity graphs show that the gap between the velocity curves decrease, as fluid moves toward the separation point. This has a significant effect on the final volume of fluid flowing as at the separation point the fluid splits evenly. It was also found that the degree of fluid penetration is affected by the web flexibility and permeability. It has also been found that viscoelastic parameter and ratio of viscous to elastic forces have great impact on the emerging parameters, furthermore, the pressure gradient has been significantly affected with the variation in permeability and deformability. It is worth mentioning that the present study is a quick reference for the engineer working in coating industries and to compare the results with experimental data. Some results are shown graphically. [ABSTRACT FROM AUTHOR]

The filling of a plane gap with a non-Newtonian fluid under non-isothermal conditions is considered by assuming viscous dissipation and curing reaction induced by the heat supplied through the walls of the gap. The rheology of the medium is described by the modified Cross-WLF model accounting for the effect of temperature, strain rate intensity, and the extent of a chemical reaction on the viscosity. The curing reaction kinetics is determined by the equation based on the n-th order reaction with self-acceleration. The problem is solved numerically using an original computational technique. The curable fluid flow structure is revealed to include three characteristic zones during the filling process: a fixed layer on the solid wall with a high degree of curing; a central "core" with an almost uniform distribution of characteristics; and a transition zone serving as a "lubricating" layer between two abovementioned zones. The structure is governed by heating of the fluid through the wall, since the heating affects the rheological characteristics of the medium and the rate of the cured layer formation. Analysis of the similarity criteria for the considered flow conditions shows that the fluid flows in a creeping regime (Re < 0.01); the temperature distribution is mainly affected by convective heat transfer (Pe > 100); the influence of dissipative heating and exothermic effect of the curing reaction is insignificant. The effect of curing on the mass distribution of the liquid portions entering through the inlet section is shown. The variation of the pressure distribution is analyzed at various flow conditions. [ABSTRACT FROM AUTHOR]

Non-isothermal non-Newtonian fluid flow implemented during filling a coaxial channel in the gravity field is investigated with regard to the dissipative heating, the temperature dependence of the effective viscosity, and the presence of the free surface. The rheological behavior of the medium is described by the Сross-WLF model. The problem is solved numerically using the original computational technology based on the control volume approach and the method of invariants for satisfying the boundary conditions on the free boundary. The flow characteristics in the process of filling are demonstrated for various values of the constitutive parameters. [ABSTRACT FROM AUTHOR]

For propulsion systems using gel fuels, reducing the gel fuel viscosity is essential for achieving better atomization and combustion. In this paper, we investigate the flow and heat transfer in a water-gel with a temperature and shear dependent viscosity. We consider several different channels, mimicking the transport of gelled fuels in propulsion systems, and we also look at corrugation, which is a way of enhancing fluid mixing and thus improving the heat transfer characteristics. The rheological parameters in the constitutive model of the gel are fitted with experimental data. The influence of different corrugation profiles, corrugation configuration parameters and the Reynolds number on the mean apparent viscosity and the pressure drop are investigated. It was found that the flow recirculation formed in the valley of the corrugations enhances the heat transfer and thus the temperature of the main flow. We also noticed an increase in the pressure drop due to the stronger viscous dissipation. Furthermore, it was observed that the sinusoidal corrugation can achieve lower viscosity with a lower pressure drop compared with triangular and trapezoidal corrugations. A shorter wavelength and a deeper wave amplitude of the corrugation seemed to be better for reducing the gel fuel viscosity, while we must consider the adverse consequence of increased pressure drop. A larger Reynolds number was helpful for both lowering the pressure drop and for reducing the viscosity. In addition, compared with a smooth straight pipe, a Y-shape corrugated channel with a constant inlet velocity reduced the mean apparent viscosity by 70.8%, and this value increased to 72.6% by further applying a pulsed inlet velocity, which can greatly enhance the gel fuel atomization and thus improve the combustion efficiency. [ABSTRACT FROM AUTHOR]

The characterization of the rheological behaviors of polymer-surfactant binary mixtures is important in several applications and industrial processes. In this paper, rheological behaviors of partially hydrolyzed polyacrylamide (PHPAM) polymer and sodium dodecyl sulfate (SDS) surfactant solutions have been investigated through viscosity measurement and then mathematical regression modeling. The effects of salt (CaCl2) and alkali (NaOH) on the viscosities of these polymer-surfactant solutions have also been experimentally investigated and theoretically modeled. All polymer-surfactant systems are found to exhibit shear-thinning non-Newtonian behavior. The experimental investigations revealed that addition of salt extensively reduced the viscosity of polymer-surfactant solutions by reducing the hydrodynamic size of polymer and this peculiar effect has been explained in terms of electrical double layer (EDL). The non-Newtonian polymer-surfactant solutions became almost Newtonian when the concentration of CaCl2 exceeded some threshold value (≥4.5 × 10−2 mol.L−1 or 0.5 wt%). Presence of NaOH also reduced the viscosity significantly and explained using the theory of molecular dynamics. The Herschel–Bulkley power law model through mathematical regression fitting procedure has been used to estimate the yield stress (τ0), the consistency index (k) and the flow behavior exponent (n) and analyze the rheology results. [ABSTRACT FROM AUTHOR]

Many scientific research papers report that jet-like flow during speech is a potent route for viral transmission in the COVID-19 pandemic. Droplet emission occurs during breaking, speaking, singing, coughing and sneezing, which could be affected by the shear-thinning rheology of the liquid. Here we test the viscosity of simple liquid system in many-body dissipative particle dynamics model under different driven forces, which illustrates that the simple liquid system interestingly has shear-thinning property. Based on this, we simulate the process of jet-like flow and capture the rupture of liquid cylinder and the process of drop generation, which implies the jet-induced liquid pinchoff and drop generation can be regulated by initial driven force and its temperature. The results show that larger pressure pulse could generate longer liquid cylinder and larger drops, as well as at lower force frequency. This work can provide an insight in liquid jet-like flow with shear-thining property and yield a better understanding of virus spreading via salivary droplets. [ABSTRACT FROM AUTHOR]

An experimental investigation is conducted to study the influence of shear‐thickening behavior on the primary breakup process of suspension jets. The primary breakup morphologies of cornstarch–water suspension are observed via a high‐speed camera. The unique hardened breakup mode only occurs when the suspension exhibits discontinuous shear thickening (DST). During hardened breakup mode, the oscillating portion of the suspension jet becomes perpendicular to the air direction and keeps cylindrical instead of deforming into a thin sheet or membrane structure. The suspension jets break off into large pieces rather than tiny droplets. The dimensionless number N is established to describe the relative magnitude of the increment of the viscous force and aerodynamic force during the primary breakup process. The primary breakup regime map of Newtonian fluids and shear‐thickening suspensions is also promoted based on the dimensionless number N and the Weber number We. [ABSTRACT FROM AUTHOR]

Copyright of Revista Brasileira de Engenharia Agricola e Ambiental - Agriambi is the property of Revista Brasileira de Engenharia Agricola e Ambiental and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Challenges in classical and non-Newtonian fluid mechanics are abundant, particularly when viewed from a mathematical perspective. Classical fluid mechanics, based on Newtonian principles, deals with the behavior of simple fluids like water and air. However, challenges arise when dealing with complex fluids that do not follow Newton's linear relationship between stress and strain rate. One significant challenge is the mathematical description of non-Newtonian fluids, which often require sophisticated constitutive equations to capture their behavior accurately. These equations must account for shear-thinning, shear-thickening, viscoelasticity, and other complex rheological properties. Finding appropriate mathematical models that can predict these behaviors under various conditions is a formidable task. Additionally, solving the governing equations of fluid mechanics, the Navier-Stokes equations, poses significant mathematical challenges, especially in the context of non-Newtonian fluids. These equations are notoriously difficult to solve analytically and often require numerical methods, which can be computationally intensive. Understanding the stability and turbulence of non-Newtonian flows is another mathematical challenge. Turbulent flows of complex fluids exhibit unique characteristics that differ from those of Newtonian fluids, requiring advanced mathematical tools to analyze and predict their behaviour. [ABSTRACT FROM AUTHOR]

• Radial displacement of Newtonian-Non-Newtonian fluids in Hele-Shaw cell was studied. • Paraffin and carboxymethyl cellulose were Newtonian and Non-Newtonian fluids. • Tip-splitting and dendritic patterns were observed during the interfacial developments. • In contrast with literature, interfacial instability decreased in low concentration of CMC solution. • Low interfacial tension and high zero-shear viscosity were the main reasons for this contradiction. We report on experimental study of interfacial instability in immiscible Newtonian-Non-Newtonian radial displacement occurs in Hele-Shaw cell where liquid paraffin was injected to displace carboxymethyl cellulose (CMC) solution. For the benchmark system, tip-splitting pattern was observed. Results indicated that the maximum change in the shear rate and viscosity of CMC solution occurs in the very early stage of the displacement process. The comparison between Newtonian-Non-Newtonian and Newtonian-Newtonian interfacial development, showed higher number of fingers for Newtonian displacement, but wider and longer fingers for non-Newtonian system. Investigation of concentration effect indicated that the interfacial instability decreased in displacing of 0.5%wt CMC solution. In contrast with literature, the instability increased significantly for 1.5%wt CMC solution, and dendritic pattern emerged instead of tip-splitting. This was due to the significant reduction in interfacial tension and rise in viscose forces. Moreover, the results showed that increasing the initial injection radius led to increment in fingers number and reduction in velocity of the dominant fingertip. Additionally, increasing the injection flowrate resulted in fingering pattern change from tip-splitting to dendritic type. Finally, comparing the number of the observed fingers with literature, suggested that using average capillary number; Ca ≤ 10−3, Paterson's theory may be followed by the experimental results. [Display omitted] [ABSTRACT FROM AUTHOR]

Based on the couple-stress theory, the elastohydrodynamic lubrication (EHL) contact is analyzed with a consideration of the size effect. The lubricant between the contact surface of a homogeneous coated half-plane and a rigid punch is supposed to be the non-Newtonian fluid. The density and viscosity of the lubricant are dependent on fluid pressure. Distributions of film thickness, in-plane stress, and fluid pressure are calculated by solving the nonlinear fluid-solid coupled equations with an iterative method. The effects of the punch radius, size parameter, coating thickness, slide/roll ratio, entraining velocity, resultant normal load, and stiffness ratio on lubricant film thickness, in-plane stress, and fluid pressure are investigated. The results demonstrate that fluid pressure and film thickness are obviously dependent on the size parameter, stiffness ratio, and coating thickness. [ABSTRACT FROM AUTHOR]

Computational hemodynamic (CHD) is an engineering tool and a good approach that helped many physicians to obtain much information about the situation of the patient in a lot of diseases like cardiovascular disease, even surgery, etc. The dispersion of blood cells in the plasma is heterogeneous. Therefore, the blood fluid is a multi-phase mixture of non-Newtonian fluid. Numerical calculation of non-Newtonian viscosity models of blood flow parameter includes Reynolds number; different wall heat fluxes in three situations of the body (sleeping, standing and running), etc. are investigated. To construct a 3D model of the kidney blood vessel, an open-source software program using Digital Imaging and Communications in Medicine (DICOM) and Magnetic Resonance Image (MRI) is used. Additionally, the vessel wall is considered solid. The finite volume approach and SIMPLE scheme are used. The non-Newtonian blood flow is considered as a laminar flow. All of these heat fluxes generated by the body in different situations have their impact on the reported parameters in this paper. The reported parameters included dimensionless numbers like pressure drop, average wall shear stress, heat transfer coefficient, and temperature. The power-law non-Newtonian viscosity model makes the velocity gradient more than other non-Newtonian viscosity models. Also, the power-law model represents a higher heat transfer. [ABSTRACT FROM AUTHOR]

Most traditional mold fluxes are Newtonian fluids, and their constant viscosity has certain limitations in continuous casting. A new non-Newtonian fluid mold flux with shear-thinning behavior, i.e., a mold flux with a relatively high viscosity at lower shear rates and a relatively low viscosity at higher shear rates, is required to satisfy the mold-flux performance requirements for high-speed continuous casting. The addition of a certain amount of B2O3 to a CaO–SiO2–Na2O-based mold flux can result in a shear-thinning property. To obtain an improved understanding of the mechanism of this characteristic, a molecular-dynamics simulation method was used to study the microstructural changes of the mold flux. Structural changes of mold-flux samples were analyzed and verified by Raman spectroscopy. The results of the two methods were almost the same, both resulted from the addition of B2O3 and changed the microstructure and degree of polymerization of the mold flux, which resulted in the shear-thinning property of the mold flux. This non-Newtonian fluid mold flux was used in square-billet casting tests, and the quality of the slab was improved effectively.

The Meter model (a four-parameter model) captures shear viscosity–shear stress relationship (S-shaped type) of polymeric non-Newtonian fluids. We devise an analytical solution for radial velocity profile, average velocity, and volumetric flow rate of steady-state laminar flow of non-Newtonian Meter model fluids through a circular geometry. The analytical solution converts to the Hagen–Posseuille equation for the Newtonian fluid case. We also develop the formulations to determine effective viscosity, Reynolds number, and Darcy's friction factor using measurable parameters as available rheological models do not correctly define these parameters for a given set of flow condition in circular geometry. The analytical solution and formulations are validated against experimental data. The results suggest that the effective Reynolds number and effective friction factor estimated using the proposed formulation help characterize non-Newtonian fluid flow through a circular geometry in laminar and turbulent flows. [ABSTRACT FROM AUTHOR]

The aim of this work is improving the efficiency of chemical technology processes implemented in high viscosity or non-Newtonian fluids by evaluating modes and conditions of ultrasonic action, which provide an increase in the volume of the formed cavitation area. As a result of the research, a theoretical model of cavitation area formation in the non-Newtonian medium has been developed. The analysis of the model allows to calculate the optimal intensity of ultrasonic action (for linear-viscous fluids, the optimal intensity ranges from 1.6 to 80 W/cm2; for nonlinear-viscous fluids up to 120 W/cm2) and the distance (60-125 cm) between the irradiating surface and the reflecting boundary providing the maximum cavitation area volume. Last stage of presented studies the model was confirmed experimentally. [ABSTRACT FROM AUTHOR]

We consider a Casson's model describing the blood flow through vessels with a rough microstructure. Precise analytical formulas and some apriori estimates on relation between velocity, viscosity and stress of flow were derived for stationary blood flow. We compare different flow states depending on relation between vessels' diameters and wavelength of vessel walls. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Jilin University (Science Edition) / Jilin Daxue Xuebao (Lixue Ban) is the property of Zhongguo Xue shu qi Kan (Guang Pan Ban) Dian zi Za zhi She and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The back extrusion (BE) method is a well‐known translational concentric cylinder viscometry that can analyze viscosity from the force–time curve of a cylindrical plunger pushed into a cylindrical cup filled with a sample fluid. It can analyze Newtonian, power‐law, and Herschel–Bulkley flows. However, the plunger must be moved 100 mm or more from the sample surface toward the cup bottom, any sample fluid adhering to the plunger must be removed. Moreover, given the complexity of the calculation steps, the BE method is not as widely. The short back extrusion (SBE) method proposed in this study is an improved immersed‐type BE method. By setting the measurement position inside the sample, the upflow in the annular space is smooth even over a short distance (5–15 mm). Measurement over a short distance decreases the amount of sample adhered to the plunger, mitigating the need to remove any sample from the plunger after each measurement, thereby facilitating repeated measurements. A program automatically determines flow type and, using novel mathematical formulas, it calculates the measured characteristics of the flow. In addition, the greatest advantage of the SBE method is that it can measure samples containing solids. It can be measured in a state in which a person usually eats, because the larger the stress required for the flow, the wider the gap. Moreover, its measurement accuracy is comparable to cone‐plate analysis, and the linear region of the analysis area is wide with less destructive movement. [ABSTRACT FROM AUTHOR]

Summary: In this paper, we present a simplified lattice Boltzmann method for non‐Newtonian power‐law fluid flows. The new method adopts the predictor‐corrector scheme and reconstructs solutions to the macroscopic equations recovered from the lattice Boltzmann equation through Chapman‐Enskog expansion analysis. The truncated power‐law model is incorporated into this method to locally adjust the physical viscosity and the associated relaxation parameter, which recovers the non‐Newtonian behaviors. Compared with existing non‐Newtonian lattice Boltzmann models, the proposed method directly evolves the macroscopic variables instead of the distribution functions, which eliminates the intrinsic drawbacks like high cost in virtual memory and inconvenient implementation of physical boundary conditions. The validity of the method is demonstrated by benchmark tests and comparisons with analytical solution or numerical results in the literature. Benchmark solutions to the three‐dimensional lid‐driven cavity flow of non‐Newtonian power‐law fluid are also provided for future reference. [ABSTRACT FROM AUTHOR]

A series of theoretical analysis and experimental measurements were done to analyze the characteristic of the apparent viscosity of oil-water unstable mixtures which display the similar distributions as the mixtures in pipeline flow. Based on the experimental results, it can be concluded that the unstable oil-water dispersed mixtures are always show the characteristic of non-Newtonian fluid. The shear rate has a great influence on the apparent viscosity, particular for the water-in-oil mixtures. The effect of dispersed phase volume fraction on the apparent viscosity of the unstable mixtures displays the similar rules as the stable emulsions. Also, the influences of the dispersed phase distribution and viscosity on the apparent viscosity were studied through the corresponded experiments systematically. Furthermore, a new kind of prediction model was obtained in the present study. The unstable and non-Newtonian fluid characteristics of oil-water two-phase dispersed mixtures were considered in this model to improve their range of application and the prediction accuracy. Moreover, this kind of apparent viscosity prediction model was validated by using the experimental data from some other literatures including different kinds of oils such as white oil and crude oil, and the average deviation was always less than 9% which was a great accuracy of apparent viscosity prediction. [ABSTRACT FROM AUTHOR]

Differences in the rheology and friction factor of natural food hydrocolloid gels were studied in this paper. The practical importance of the knowledge of the rheological parameters is quite evident. The experimental data were carried out using a concentric cylinder rotary viscometer. It was prepared 1% hydrocolloid solutions (hydrogels). Hydrogels of the natural gums extracted from the seeds of the plants and plant tubers have been used - carob gum (from the seeds of Ceratonia siliqua), guar gum (from the seeds of Cyamopsis tetragonoloba) and tara gum (from the seeds of Caesalpinia spinosa). Rheological behaviour has non-Newtonian pseudoplastic character and the flow curves were fitted using the Otswald - de Waele (power law) model and Herschel - Bulkley model. The hydrogels exhibit shear thinning behaviour. The meaning of the rheological parameters on the friction factors during flow of hydrocolloid gels in the tube has been shown. Information on time dependent behaviour of tested liquids has been also obtained. Time dependent curves were fitted by the Gaussian model. Preliminary results obtained for a constant shear rate showed the thixotropic and time-dependent behaviour of the hydrogels. These parameters can be especially used in much software dealing with a numerical simulation of the flow problems.

Rheological characterization and development of models for glucose syrup production process obtained from selected agricultural crops were studied. Glucose syrups were produced at 60°C, 80°C and 100°C. The rheological properties of the glucose syrups were investigated and the effect of temperature on viscosity was determined. Also, the effect of shear rate on viscosity was determined at spindle speeds of 10, 20, 50 and 100 rpm. Data obtained were fitted into Power Law model for analyzing the viscosity and for fluid classification. The starch yields were 71.7%, 85.3% and 91.5% and the syrup yields were 78.82%, 86.35% and 88.65% for maize, rice and cassava respectively. Viscosities of the syrups showed an inverse relationship with temperature and shear rates. The Power Law index (n) was found to be between 0 and 1 and the Power Law model plots showed distinct characteristics of pseudo-plastic behaviour under the classification of non-Newtonian fluid. [ABSTRACT FROM AUTHOR]

Highlights • Newtonian fluid model underestimates wall shear stress compared to non-Newtonian. • Non-Newtonian fluid models experience reduced disturbed flow compared to Newtonian. • Non-Newtonian fluid predicts reduced exposure to low and oscillatory shear stress. • Regions of high oscillatory shear index demarcate regions of flow recirculation. Abstract The development of atherosclerosis at the carotid bifurcation is impacted by local variations in wall shear stress (WSS) magnitude and direction, as well as flow complexity within the vessel. In this study, stereoscopic particle image velocimetry (PIV) was used to investigate multidirectional WSS and disturbed flow for idealized models of the carotid bifurcation with varying eccentric stenosis of the internal carotid artery (ICA) and both Newtonian (N-fluid) and non-Newtonian (nN-fluid) blood analogues. Turbulence intensity (TI) was reduced with the nN-fluid compared to N-fluid for mild to moderate stenosis, and comparable for more severely stenosed (70%) models. Differences in maximum TI due to viscosity model ranged from 0.02 m/s to 0.06 m/s compared to much larger differences due to geometry of up to 0.29 m/s between mild and severe stenosis. The level of time-averaged WSS (TAWSS) increased with stenosis severity from 5 Pa to 32 Pa, and nN-fluid led to higher WSS on average than N-fluid counterparts. Regions of elevated oscillatory shear index (OSI) demarcated recirculation regions, and mean OSI in the ICA branch was reduced for nN-fluid models by 9–19% compared to N-fluid. Transverse WSS (transWSS) increased with WSS magnitude and again was higher in nN-fluid models. Surface area exposure to shear metrics indicated that a Newtonian viscosity assumption predicted larger regions of low and oscillatory WSS, while predicting reduced regions of high transWSS, in comparison to the more physiological shear thinning fluid. [ABSTRACT FROM AUTHOR]

This paper focuses on the mathematical analysis of a self-suggested model arising from biology, consisting of dynamics of oxygen diffusion and consumption, chemotaxis process and viscous incompressible non-Newtonian fluid in a bounded domain Ω ⊂ Rd, with d = 2,3. The viscosity of the studied fluid is supposed to be non constant and depends on the shear-rate |Dv| as well as the cell density mm and the oxygen concentration c. Nonlinearities are also considered in the diffusion terms for the convection-diffusion equations corresponding to m and c. Under the choice of suitable structures and convenient assumptions for the nonlinear fluxes, we prove global existence of weak solutions, in the case of a smooth bounded domain subject to Navier's slip conditions at the boundary and for large range of initial data. [ABSTRACT FROM AUTHOR]

Transporting slurry is a difficult task and industries use a kinetic or centrifugal pump or a screw or progressive cavity pump to deliver it. On the other hand, approximation models can help predicting performance and avoiding the expensive experiments of pumps with slurries. In this work, bentonite-based slurries were prepared and pumped by a centrifugal pump and a progressive cavity pump. The experimental facilities were developed in-house and artificial neural network-based approximation models were developed to predict performances. The approximation models say that it can eliminate the expensive testing to draw performance curve a pump. The relative merits of the pumps show that the progressive cavity pump has a better capability to handle the slurries or high viscosity fluids. [ABSTRACT FROM AUTHOR]

[Display omitted] • Onset of internally heated convection is constrained for power-law viscosity. • Localized convection is possible for power-law viscosity. • Thresholds for the onset of localized and widespread convection are similar. We use two-dimensional numerical simulations to investigate the finite-amplitude onset of convection in internally heated, infinite Prandtl number fluids with strongly temperature-dependent, power-law viscosity. We focus on the stagnant-lid regime which is relevant to planetary interiors. We find that convection can occur in both the usual, widespread convection planform, where the convection cells form in the entire layer, as well as the localized convection planform characterized by a single upwelling surrounded by a nearly stationary fluid. The critical Rayleigh number for the onset of convection by finite-amplitude perturbations is nearly independent of the convection planform in a broad range of the spacings between upwellings, from of the order of the depth of the layer to up to infinity. A simple heuristic analysis suggests scaling relationships which fit the numerical results in the stagnant-lid regime for an arbitrary power-law exponent, n > 1. The results of this study provide new fluid dynamical constrains on the threshold for convection in planetary interiors. [ABSTRACT FROM AUTHOR]