Shear-thinning Nature Research Articles

Construction of optimised theoretical model using ANOVA -Taguchi methodology for transient flow of Carreau nanofluid through microchannel prone to radiation

The current study intends to predict the optimised condition to attain the objective of acquiring highest heat transfer rate to develop an efficient model. The transient flow of Carreau nanofluid within a microchannel when channel walls are susceptible to radiation is contemplated. Buongiorno model is employed, which emphasizes the repercussions of Brownian motion and thermophoresis phenomena; also, mixed-convective flow is accounted. The modelled problem gives rise to partial differential equations, which are non-dimensionalized employing non-dimensional quantities. The resultant equations are solved numerically using the finite difference method. Results of analysis demonstrate that the Weissenberg number for n<1 depicts shear thinning nature, and for n>1, depicts shear thickening nature, decreasing velocity. The skin friction coefficient increases when solutal Grashof number rises for the high range of the Reynolds number. The Sherwood number increases when Schmidt number is less for increased value of Reynolds number. Optimization method reveals the highest heat transfer rate of 7.3687 for the considered model. ANOVA results show that the manipulation of Reynolds number is crucial with 57.29% impact and the manipulation of Prandtl number has minor impact of 1.41%on Nusselt number. Shear thinning nature of Carreau fluid finds its application in extrudability, printability and injectability and shear thickening nature is extensively used in industrial polishing, explosion resistance.

Dispersion of a non-uniform solute slug in pulsatile viscoelastic fluid flow

Solute transport in pulsatile viscoelastic fluid flow is relevant in nutrient transport and drug delivery in blood flow. Previous studies have extensively analyzed the effect of the shear-thinning nature of the blood but neglected the elastic property. The present study aims to fill this lacuna by analyzing the role of blood viscoelasticity on solute transport. To accomplish this, we study solute transport for a non-uniformly distributed solute slug in the pulsatile flow of an Oldroyd-B fluid through a tube in the presence of wall absorption. We employ Gill's procedure and Aris' method of moments to compute the transport coefficients Km(t) (m≤4). We also numerically solve the species transport equation using a finite difference scheme to directly determine local solute concentration C(t,z,r). Consistent results for a non-viscoelastic fluid predict a negative convection coefficient K1 and a positive effective diffusivity K2 for realistic values of the parameters. However, the present analysis predicts positive K1 and negative K2 for small tubes due to flow reversal caused by the fluid elasticity. For high Λ1, the amplitude of oscillation for K1 and K2 exhibits scaling K1∼Λ11.5 and K2∼Λ12 indicating an enhancement in the dispersion due to fluid elasticity, where Λ1 is the dimensionless relaxation time. The analysis of the skewness and (excess) kurtosis coefficients reveals inconsistency in previous studies on Newtonian fluids. Thus, we present consistent results not only for a viscoelastic fluid but also for a Newtonian fluid subjected to a pulsatile pressure gradient. In addition, the solute dispersion is significantly influenced by the non-uniformity of a solute slug. As the radius of a slug increases, solute dispersion reduces in short and moderate times; however, at large times, it is independent of the radius of a slug.

Optimizing rheological characterization for extrusion-based additive manufacturing of Zirconia ceramic inks with varied Yttria content stabilization

This study explores the rheological properties of zirconia-based ceramic inks, focusing on TZ-3YSB alongside newer variants such as Zpex, Zpex-4, and Zpex-smile, distinguished by their varying Y2O3 content. Through comprehensive analysis, it was found that these ceramic inks exhibit non-Newtonian behavior, which is notably influenced by the ceramic loading content and particle aggregation. Moreover, the shear-thinning nature observed in these inks proves advantageous, as it enables easier extrusion through smaller nozzles at reduced pressure levels. The implications of these findings are discussed in detail, shedding light on the complex interplay between rheological properties and ceramic ink composition, thus offering valuable insights for optimized three-dimensional printing (3DP) production processes - contributing to strengthening crowns, bridges, and implants, enhancing aesthetics, and ensuring biocompatibility for dental prostheses.

Entropy production associated with magnetohydrodynamics (MHD) thermo-solutal natural convection of non-Newtonian MWCNT-SiO2-EG hybrid nano-coolant

This article investigates the convective thermal and solutal exchange from the active walls of a trapezium chamber which is filled with multi-walled carbon nanotubes (MWCNT)-silicon dioxide (SiO2)-ethylene glycol-water hybrid nano-coolant. The hybrid nano-coolant exhibits non-Newtonian shear-thinning rheology and is modeled by the power-law viscosity as per an exploratory report. The convection is generated by both the thermal and solutal buoyancy forces in the presence of a magnetic field. Thermophysical properties of the particular nano-coolants are estimated from the temperature-dependent empirical correlation. An in-house FORTRAN code based on the finite volume method (FVM) has been utilized to simulate the non-dimensional controlling equations representing the physical model. By systematically varying the strength of the magnetic field (Ha=0−50) and its direction (δ1=0−90), the volume fraction of nano-coolant (ϕ=0−0.04) and solutal-to-thermal buoyancy ratio (N=−2 to 2), we thoroughly analyzed their impact on the flow field, thermal, and solutal transmission behavior. Significant impacts arising from the shear-thinning nature (n<1) of the nano-coolant were observed, influencing both thermal and solutal transfer rates as reflected in the Nusselt number (Nu) and Sherwood number (Sh). The impact of Ha on Nu and Sh is more substantial for n<1 than the case n=1. The investigation exposed that when Ha=30,δ1=30∘ the average Nu (Nu‾) for nano-ccolants (ϕ=2%) is maximally enhanced by 80% for n=0.6 compared to the case n=1.0. For the same nano-coolant with Ha=30 and δ1=90∘, there is a 128% elevation in the average Sherwood number (Sh‾) when n=0.6 compared to n=1.0. The entropy generation (S‾) inherent to the heat and mass transfer process and hence a criterion (ξ=S‾/Nu‾) is computed to address the system thermal performance from the thermodynamics second law. S‾ increased as n was reduced, indicating that the shear-thinning effect contributed strongly to the entropy generation.

Biopolymer-enhanced delivery of reactive sulfide reagents for in-situ mercury remediation of heterogeneous contaminated soils

Mercury pollution from natural and anthropogenic sources demands effective remediation. This study focuses on optimizing a chemical stabilization approach using sulfur-containing compounds to create stable mercury sulfide (HgS) and immobilize elemental mercury in polluted soils. We propose using xanthan gum biopolymer to enhance the in-situ delivery of sulfide microparticles, overcoming soil heterogeneities due to its non-Newtonian behavior. Stability tests indicated that increased biopolymer concentration enhances particle stability due to the viscous and shear-thinning behavior of the polymer solutions. Various combinations (12 solutions) of xanthan polymer, pyrite microparticles, and sulfide-containing reagents were tested in batch experiments. Pyrite microparticles slightly reduced the xanthan solution's viscosity while retaining its non-Newtonian character. All solutions effectively transformed liquid mercury droplets into cinnabar, demonstrating successful mercury stabilization. Notably, solutions containing PIAX and SIPX, xanthate organosulfur compounds, significantly reduced the dissolved concentration of elemental mercury. Column experiments demonstrated xanthan gum's superior performance for in-situ injection of pyrite microparticles and sulfide mixtures into the soil compared to conventional water injection. At a polymer concentration of 4 g/L, a stable displacement front and an 88 % recovery of the initially injected particle-suspension density were achieved. The combined effects of xanthate's floating behavior and xanthan gum's shear-thinning nature substantially enhanced the delivery of pyrite microparticles in porous media for soil mercury remediation. This combination reduced the aqueous elemental mercury concentration in artificially polluted sand by up to 97 %, particularly with the xanthate organosulfur compound, PIAX. Xanthate has a higher potential to react with elemental mercury to form cinnabar compared to sodium thiosulfate. Additionally, the pyrite microparticles, rendered hydrophobic in xanthate solutions, integrated into the mercury droplets, forming a black paste. This study introduces a promising approach for efficient elemental mercury stabilization in contaminated soils by integrating biopolymers, reactive soluble compounds, and pyrite microparticles for sustainable decontamination.

FRESH-based 3D bioprinting of complex biological geometries using chitosan bioink

Traditional three-dimensional (3D) bioprinting has always been associated with the challenge of print fidelity of complex geometries due to the gel-like nature of the bioinks. Embedded 3D bioprinting has emerged as a potential solution to print complex geometries using proteins and polysaccharides-based bioinks. This study demonstrated the Freeform Reversible Embedding of Suspended Hydrogels (FRESH) 3D bioprinting method of chitosan bioink to 3D bioprint complex geometries. 4.5% chitosan was dissolved in an alkali solvent to prepare the bioink. Rheological evaluation of the bioink described its shear-thinning nature. The power law equation was fitted to the shear rate-viscosity plot. The flow index value was found to be less than 1, categorizing the material as pseudo-plastic. The chitosan bioink was extruded into another medium, a thermo-responsive 4.5% gelatin hydrogel. This hydrogel supports the growing print structures while printing. After this, the 3D bioprinted structure was crosslinked with hot water to stabilize the structure. Using this method, we have 3D bioprinted complex biological structures like the human tri-leaflet heart valve, a section of a human right coronary arterial tree, a scale-down outer structure of the human kidney, and a human ear. Additionally, we have shown the mechanical tunability and suturability of the 3D bioprinted structures. This study demonstrates the capability of the chitosan bioink and FRESH method for 3D bioprinting of complex biological models for biomedical applications.

Insight into the electroosmotic vortex modulated reaction characteristics of viscoplastic fluids

Using positively charged patches embedded in the walls of a microreactor, we generated electroosmotic vortices to analyze chemical reactions involving the flow of viscoplastic species. Reactant species A and B undergo a reaction to produce species C, which possesses physical properties suitable for biomedical applications. We developed a modeling framework, extensively validated with the available experimental results as well, to solve relevant transport equations considering pertinent boundary conditions. By varying parameters, such as the Bingham number, diffusive Peclet number, relative concentration of species B, flow-behavior index, and Damkohler number within physically justified ranges, we examined the flow field, species concentration, average product concentration, and generated species flow rate. Our findings indicate that the liquid yield stress and shear-thinning nature strongly influence vortex strength and the structure of yielded and unyielded regions. Notably, electroosmotic vortices enhance product species concentration compared to cases without vortices across the chosen range of diffusive Peclet numbers, providing convective mixing strength for reactants. For lower Bingham number values, product concentration trends increase then decrease with increasing Peclet numbers, whereas for higher Bingham numbers, it exhibits a monotonic decrease. Additionally, lower Bingham numbers lead to increased average product concentration as flow-behavior index decreases, while higher Bingham numbers show the opposite trend. Furthermore, average product concentration increases up to critical Damkohler number values for smaller Bingham numbers but becomes insensitive to Damkohler number changes with greater Bingham numbers. These insights of our analysis pave the way for designing innovative, highly effective microreactors largely used for biochemical and biomedical applications.

A Metabolomics Approach to Establish the Relationship between the Techno-Functional Properties and Metabolome of Indian Goat Yoghurt.

Goat milk has poorer fermentation characteristics due to the absence or only traces of αs1-casein, due to which goat yoghurt contains a less dense gel structure. Moreover, the fermentation characteristics of the milk vary between the breeds of the same species. Therefore, it becomes imperative to explore a few metabolites which could regulate the techno-functional properties of goat yoghurt. This study was aimed at relating the metabolite profile of yoghurt prepared from milk of Barbari, an indigenous goat breed of India, and its techno-functional properties (firmness, whey syneresis, and flow behaviour) using multivariate data analysis and regression models. Goat yoghurt was prepared with two different total solids (TS) levels (12 and 16%) and cultures, namely, commercial culture comprising a thermophilic yoghurt culture (A) and NCDC-263 comprising a mixed yoghurt culture (B). Results demonstrated a significant difference (p < 0.05) in whey syneresis with the increase in the TS level. Flow behaviour of all yoghurt samples showed a decrease in viscosity with an increase in shear rate, which confirmed its non-Newtonian behaviour and shear thinning nature, whereas frequency sweep confirmed its viscoelastic nature. Firmness was the most affected under the influence of different TS and culture levels. It was higher (p < 0.05) for 16-A, followed by 16-3B, and minimum for 12-2B. GC-MS-based metabolomics of the yoghurt revealed a total of 102 metabolites, out of which 15 metabolites were differentially expressed (p < 0.05), including 2-hydroxyethyl palmitate, alpha-mannobiose, and myo-inositol. Multivariate data analysis revealed clear separation among groups using principal component analysis and several correlations using a correlation heat map. Further, regression analysis exhibited methylamine (0.669) and myo-inositol (0.947) with higher regression coefficients (R2 values) exceeding 0.6, thus demonstrating their significant influence on the techno-functional properties, mainly firmness, of the yogurt. In conclusion, A gas chromatography-based metabolomics approach could successfully establish a relationship between the metabolome and the techno-functional properties of the yoghurt.

Effects of elevated ground temperatures on properties of cement grouts for deep rock grouting

AbstractAppropriate determination of the mix ratios of cement grouts is of vital importance to the quality of rock grouting and the risk reduction of groundwater inflow. The behavior of grout, often highly temperature dependent, is likely to be affected by the elevated ground temperature in deep rock masses. This paper aims to experimentally gain insights into the effects of elevated ground temperatures on the properties of cement grout in fresh and hardened states in deep rock grouting. The results revealed that a temperature of 35°C is crucial for changes in the properties of thick cement grout with a water–cement ratio of less than 0.8. When the temperature is up to 35°C, there can be significant improvements in rheological parameters, acceleration of grout setting, and increase in the rheological time dependence of thick cement grout; however, there may also be a slight impact on the initial grout flowability and the nature of shear thinning. The high temperature may still improve the stability of fresh cement grout and also improve the porosity and creep deformation of hardened cement grout considerably. The proposed constitutive model that couples the Burgers model with a fractional derivative‐based Abel dashpot in the series can be used to characterize the creep behavior of hardened cement grout appropriately. The paper provides a valuable reference for optimization of mixture design of cement grouts, thus enhancing deep rock grouting quality and improving safety.

Electroosmosis of viscoelastic fluids in pH-sensitive hydrophobic microchannels: Effect of surface charge-dependent slip length

We analytically investigated the electroosmotic flow characteristics of complex viscoelastic liquids within a charged hydrophobic microchannel, considering the pH and salt concentration-dependent surface charge effects in our analysis. We examined the variation of the electric-double layer (EDL) potential field, the surface charge-dependent slip (SCDS) length, the flow field, the viscosity ratio, and both normal and shear stresses in relation to the bulk pH, bulk salt concentration, and Deborah number of the solution. Our current findings indicate that, under strong flow resistance due to increased electrical attraction on counter ions, a highly basic solution with a high EDL potential magnitude results in a significant decrease in the slip length. Neglecting the effect of SCDS leads to an overestimation of flow velocity, with this overprediction being more pronounced for highly basic solutions. This overestimation diminishes as bulk salt concentration increases, particularly when compared to strongly acidic solutions. Furthermore, a noticeable increase in average velocity is observed as the Deborah number rises for highly basic solutions compared to highly acidic ones. This is attributed to the substantial reduction in apparent viscosity caused by the shear-thinning nature of the liquid at higher shear rates, supported by a larger zeta potential modulated strong electrical force for basic solutions. Additionally, we found that the intensity of shear and normal stresses tends to increase with bulk pH, primarily due to the rise in electric body force at higher zeta potential. These results can potentially inform the design and development of a compact, nonmoving electroosmotic pump for transporting biological species with varying physiological properties, such as solution pH. This technology could be applied in subsequent processes involving mixing, separation, flow-focusing for cell sorting, and other related applications.

Machinability and mechanism of abrasive flow machining ultra-precision surface with orientated grinding marks

The loud noise in electric automobile caused by the overlap between orientated grinding marks with meshing line on ground gear tooth surface becomes a big problem for both drivers and manufacturers. Relying on the excellent self-deformation features and trace material removal, the abrasive flow machining (AFM) process exhibited potential machinability for above ultra-precision ground surface. Benefiting by the pseudo network structure, the abrasive media would possess both excellent elasticity and fluid capability, which could be quantitatively reflected by storage modulus, loss modulus and shear thinning nature in rheological properties. Meanwhile, deriving from the CFD simulation, the media exhibited the steady flow velocity and shear stress at the finishing channel, potentially contributing to the finishing uniformity on the target ground channel, which was subsequently confirmed by the change of ground surface morphology and profiles at the initial and finished state. Most convex peaks and concave valleys have been effectively subdued and whittled, leading to a rather smoother surfaces than initial ones. Besides, on account of the different collision position between grains with convex peaks, the finishing mechanism on ground surfaces with orientated marks could be elaborated as the transition effect from directly fractured material removal on convex peak cusp into plastic deformation on residual convex peaks. Combining with the interaction between continuous matrix and discrete grains in flow field, the mechanics on single grain was systematically investigated to establish the material removal theoretical model. Generally, the AFM technique exhibited the stunning machinability on ultra-precision ground surface.

Optimizing gluten-free pasta quality: The impacts of transglutaminase concentration and kneading time on cooking properties, nutritional value, and rheological characteristics

This study investigated the influence of transglutaminase (TG) concentration and kneading time on gluten-free pasta's quality, texture, and nutritional content. Pasta dough composed of red rice, white quinoa, and tapioca flour was examined under seven treatment conditions. Variations in TG concentration (1%db, 1.5%db, and 2%db) and kneading time (5, 10, and 15 min) were applied. The findings demonstrated that as TG concentration and kneading time increased, cooking properties improved, evidenced by reduced pasta mass loss and increased swelling index and final moisture content. Furthermore, higher TG concentration and extended kneading enhanced pasta firmness to 9.1N, cohesiveness to 0.512, and chewability to 4.7 J. The treatment of 1.5% TG concentration and 10 min of kneading significantly maximized phenolic compound content with an increase from 17.54 mgGAE/100g to 39mgGAE/100g suggesting superior nutritional value. Rheological analysis revealed a distinct transition from Newtonian to non-Newtonian behavior, with the dough's shear-thinning nature becoming more noticeable as TG concentration and kneading time increased. This study provides a crucial understanding of the impacts of TG concentration and kneading time on gluten-free pasta, offering an effective strategy for optimizing pasta production processes.

Reaction characteristics of non-Newtonian species in a microreactor: The role of electroosmotic vortices

With a focus on biochemical applications and utilizing relevant physical properties, the current study numerically analyzes the impact of electroosmotic vortex and fluid rheology on the chemical reaction characteristics of species. This is achieved by installing integrated positively charged patches on the extended region of the microreactor with three inlets for injecting the reactants and generating the electroosmotic vortex. In order to produce species “C” in the extended region of the microreactor, it is presumed that reactant species “A” is injected through the upper and lower inlets and reactant species “B” is injected via the intermediate inlet. To solve the associated transport equations with appropriate boundary conditions, a thorough theoretical framework is developed. The results show that the ability of the reactant species to react is boosted when vortices form in the microreactor, increasing the convective mixing strength for reactant species. Furthermore, the fluid rheology significantly affects the reaction characteristics, which is a noteworthy finding. For fluids exhibiting a higher shear-thinning nature, the average concentration of the produced species follows an increasing–decreasing trend with the Carreau number. Additionally, it becomes apparent that the influence of the Damkohler number on the average generated species concentration is negligible at lower Carreau numbers, but it increases with the Damkohler number at higher Carreau numbers. The study also reveals that both rheological and chemical parameters have a substantial impact on the flow rate of product species. Overall, the findings of this investigation provide valuable insights for the development of technologically advanced electroosmotic microreactor capable of effectively generating the intended product species.

Oscillatory and rotational rheological characterization of jackfruit peel cellulose suspension: Effect of concentration, pH and ionic strength

Jackfruit peel (JP) is considered as an agro-industrial lignocellulosic waste which can be utilized for cellulose isolation. In this work, a yield of 25.6% cellulose was obtained from JP powder through alkali (NaOH) and bleaching (NaClO2) treatment along with the elimination of lignin, hemicellulose and other non-cellulosic constituents. The IR spectroscopy confirmed the existence of cellulose content in the final extracted product. The SEM images and EDX spectra demonstrated the microstructure of cellulose fibrils and their major elemental components as carbon and oxygen, respectively. The XRD data validated the crystalline (69.42%) nature of the cellulose. The various rheological attributes of cellulose suspension like the flow properties and dynamic rheological characteristics were examined at different pH, ionic strength and cellulose concentration. The cellulose suspensions exhibited shear thinning nature for all the pH, ionic concentration and cellulose concentrations. The change in viscoelastic behaviour of the cellulose suspension was noticed with the rise in storage modulus (G′) value with ionic concentration. The pH of the cellulose suspension had a significant impact on its viscoelastic properties due to the modifications in interfibrillar interactions of cellulose fibrils. The temperature ramp test showed that the G’ is independent of the heating of cellulose suspension from 20 °C to 80 °C. The creep and thixotropic recovery test revealed that upon removal of stress, there is the recovery of strain and viscosity up to a certain extent, which is a characteristic property of viscoelastic material.

Rheo‐kinetic study of 4‐(Dimethylsilyl) butyl ferrocene‐grafted HTPB‐based composite propellant and evaluation of casting rate

AbstractThe flow behaviour of 4‐(Dimethylsilyl) butyl ferrocene‐grafted HTPB‐based composite propellant (P01) and basic aluminized HTPB‐based propellant (P02) was investigated using shear rheometer. The experimental data were fitted to ‘power law’ for non‐Newtonian fluid flow, and the rheological parameters were expressed as consistency index (k) and pseudoplasticity index (n). For both the propellant compositions, a shear thinning nature (pseudoplasticity index; n &lt; 1) has been observed. The study categorically showed that the incorporation of 4‐(Dimethylsilyl) butyl ferrocene‐grafted HTPB has resulted in increased consistency index (k) and yield stress as compared to HTPB based compositions. In addition, the time–temperature cure‐kinetics study suggested that the rate of curing reaction is higher with toluene diisocyanate as compared to isophorone diisocyanate and the Arrhenius activation energy (Ea) corroborated with the observed trend. Furthermore, the Haegen–Poisseuille equation modified for non‐Newtonian fluid flow has been employed to determine the theoretical casting rate for 4‐(Dimethylsilyl) butyl ferrocene‐grafted HTPB‐based composite propellant at different temperatures in a vacuum casting setup.

Nanocomposite of binary colloids in effective CO2 utilization in porous media for enhanced oil production and wettability alteration

Carbon dioxide injection is a renowned enhanced oil recovery method, where the inclusion of a novel material is appreciated via mobility control of injected CO2 during flow through porous and permeable oil reservoirs. Therefore, the combination of nanoparticles and their associated additives is recommended for foam flooding schemes. Thus, this study reports the use of nanocomposites of SiO2 (0.1 – 2 wt%) and TiO2 (0.1 wt%) in promoting CO2 utilization in oil recovery projects. The assessment of a foam emulsion is a crucial and interesting task to understand the basic fundamental of three-phase interactions viz., Crude oil (oil phase), nanocomposites (aqueous phase), and CO2 (gas phase) in the context of foam-emulsion, and was examined via microscopic and rheological characterization. CO2 foam showed temperature tolerance capability and a shear-thinning viscoelastic nature due to the inclusion of nanocomposites. Furthermore, wettability alteration was understood via contact angle measurements between CO2 and nanocomposite. Interestingly, the contact angle was reduced to 39° after the inclusion of 0.1 wt% TiO2 and CO2 in the system. Finally, nanocomposite stabilized CO2 foam demonstrated a total cumulative oil recovery of 78 % at (40 °C), higher than the cumulative oil recovery (70 %) associated with nanocomposite without CO2. The results of this study suggest that CO2 utilization for oil recovery can be enhanced by developing its viscous foam, stabilized by a nanocomposite of SiO2 and TiO2 nanoparticles.

Theoretical and numerical analysis on finishing mechanism by rheological properties and flow behaviors of abrasive media in micro-porous structures

As one of the typical micro-porous structures, how to effectively finish the spray nozzles to remove the fabricated defects becomes the key problem to be urgently solved. In virtue of the unique viscoelastic characterization and excellent shear thinning nature, the abrasive media could smoothly penetrate through the micro spray holes and generate desired finishing effect. Through systemically investigating the rheological behaviors, the media obviously exhibited considerable storage modulus (around 33,000 Pa), loss modulus (around 17,000 Pa) and rather low shear viscosity, revealing the positive elasticity and fluidity equipped by media. Despite the existence of stress relaxation behavior (around 60 s), the polymer chains still remained the great stretched state resulting from the shrink of streamline when flowing into spray holes, as demonstrated by simulation results. By synthesizing the micro size effect, rheological behavior and morphology change, the finishing mechanism on spray holes was described in detail and verified by the groves and residual grains in finished surface. Besides, the bulges and burrs in the inlet of spray hole have been completely removed and the volumetric rate of finished nozzles was around 0.824 L/min, meeting the required value. In addition, by means of the yield strain-stress criteria and the grains geometry, most of grains exhibited excellent capability to initiate the plastic deformation, denoted by the critical angle range enough to generate plastic deformation. Considering both the discrete grains phase and continuous polymer phase in media, the forces on single grain were systemically investigated to establish the relevant mechanics model to theoretically describe the finish mechanism.

Exploring the Impact of Nanomaterials on Heat- and Mass-Transfer Properties of Carreau-Yasuda Fluid with Gyrotactic Bioconvection Peristaltic Phenomena

This research aims to investigate the impact of nanomaterials on the heat and mass transfer properties of fluids, with a particular focus on exploring the bioconvection phenomena. To achieve this, the study considers Carreau-Yasuda (CY) fluid, which is known for its shear thickening and thinning nature. The effects of a porous medium, radiation, and viscous dissipation are also considered to analyze heat-transfer rates. Velocity and thermal slip constraints are applied to the wall, while zero-mass flux conditions explain the concentration behavior of nanomaterials at the wall. The governing equations and conditions are simplified using a lubrication approach, and a numerical approach is used to solve the final equations with the help of constraints. The velocity, temperature, and concentration of nanomaterials and gyrotactic microorganisms are analyzed through graphs. The study finds that increasing the thermophoresis parameter leads to an increase in the concentration of nanomaterials. However, the opposite trend is noticed for the concentration of motile microorganisms. The results suggest that the addition of nanomaterials to fluids can significantly impact heat- and mass-transfer properties, and may have implications for biological processes.

Vortex-assisted electroosmotic mixing of Carreau fluid in a microchannel.

Pertaining to the mixing of the non-Newtonian Carreau fluid under electrokinetic actuation inside a plane microchannel, we propose a new design of micromixer that involves inserting a two-part cylinder bearing zeta potential of the same sign but different magnitude in the upstream and downstream directions. We numerically solve the transport equations to predict the underlying mixing characteristics. We demonstrate that a substantial momentum difference between the microchannel's plane wall and cylinder leads to the development of a vortex in the flow pathway, which in turn, enhances mixing substantially. As shown, for a fluid having a highly shear-thinning nature, the vortex-assisted convection mixing strength increases with diffusivity of the candidate fluids. Moreover, it is shown that for the higher shear-thinning nature of the candidate fluid, an increase in cylinder radius enhances mixing efficiency and flow rate simultaneously, resulting in a "quick and efficient" mixing condition. Additionally, the fluid rheology significantly alters the kinetics of shear-induced binary aggregation. Our findings show that the shear-induced aggregation characteristic time sharply increases with increasing shear-thinning behavior of the fluid.

Multi-scale analysis of solute dispersion in non-Newtonian flows in a tube with wall absorption

This study presents the two-dimensional concentration distribution of a solute cloud for non-Newtonian fluid in a tube flow with wall absorption. The non-Newtonian fluid models, such as the Carreau–Yasuda and Carreau fluid models, are helpful in investigating solute dispersion in the bloodstream and have also been effective in understanding hemodynamics. The multi-scale method of homogenization is used here to analyze the dispersion of solute through a straight tube for Carreau–Yasuda and Carreau fluids, which represents the shear-thinning nature. Most of the previous studies are mainly focused on determining the dispersion coefficient and mean concentration distribution for non-Newtonian fluids. Apart from those in our study, we also derived analytical expressions for the two-dimensional concentration distribution for Carreau–Yasuda and Carreau fluids. As the exact peak position of the two-dimensional concentration is a concern in real-life applications rather than that of mean concentration, the effects of wall absorption parameter (α*), the Weissenberg number (We), Yasuda parameter (a), and power-law index (n) on solute concentration distribution are discussed. Comparison between the present results and previous results of solute dispersion for non-Newtonian as well as Newtonian fluids are also enclosed in this study. Results reveal that the mean concentration decreases with increasing values of We because of an increase in the dispersion coefficient. Carreau–Yasuda and Carreau fluids act like Newtonian fluid for very small values of We. At the initial stage, the solute concentration exhibits transverse non-uniformity and then becomes uniform over a larger timescale. The effects of non-Newtonian parameters such as We, a, and n on transverse variation are also studied. It is noted that parameters n, We, and a have no significant impacts on the non-uniformity of the transverse concentration variation on both sides of the tube centroid, but that is not the case for the wall absorption parameter. It is observed that wall absorption results in significant transverse concentration non-uniformity across the tube cross section even after large times.