Increasing Shear Rate Research Articles

Modification of Xanthan Gum with Methyl Methacrylate and Investigation of Its Rheological Properties

Xanthan gum modification is considered a significant step in improving shearing, thermal degradation performance, and rheological properties. This paper investigates the rheology properties of the grafted copolymer based on xanthan gum and methyl methacrylate (XG-g-MMA), including shear stress and viscosity versus shear rate. The grafted copolymer XG-g-MMA was synthesized with different composition ratios of methyl methacrylate (MMA) (1:1.6, 1:5, and 1:8 wt.%) in the presence of a potassium persulphate initiator. Fourier transform infrared spectroscopy (FTIR) characterized the obtained grafted xanthan gum (XG) to confirm the grafting process. The results of the rheology analysis show that grafted XG exhibited higher shear stress and viscosity than pure XG. However, increasing the MMA ratio increases shear stress and viscosity with increasing shear rate. In addition, the rheology measurement of the grafted copolymer showed non-Newtonian shear thinning behavior for XG and XG-g-MMA. These results can further its application in different fields, such as oil recovery and pharmaceuticals.

Two dimensional computational model coupling myoarchitecture-based lingual tissue mechanics with liquid bolus flow during oropharyngeal swallowing

Biomechanical relationships involving lingual myoanatomy, contractility, and bolus movement are fundamental properties of human swallowing. To portray the relationship between lingual deformation and bolus flow during swallowing, a weakly one-way solid-fluid finite element model (FEM) was derived employing an elemental mesh aligned to magnetic resonance diffusional tractography (Q-space MRI, QSI) of the human tongue, an arbitrary Lagrangian-Eulerian (ALE) formulation with remeshing to account for the effects of lingual surface (boundary) deformation, an implementation of patterned fiber shortening, and a computational visualization of liquid bolus flow. Representing lingual tissue deformation in terms of its 2D principal Lagrangian strain in the mid-sagittal plane, we demonstrated that the swallow sequence was characterized by initial superior-anterior expansion directed towards the hard palate, followed by sequential, radially directed, contractions of the genioglossus and verticalis to promote lingual rotation (lateral perspective) and propulsive displacement. We specifically assessed local bolus velocity as a function of viscosity (perfect slip conditions) and observed that a low viscosity bolus (5 cP) exhibited maximal displacement, surface spreading and local velocity compared to medium (110 cP, 300 cP) and high (525 cP) viscosity boluses. Analysis of local nodal velocity revealed that all bolus viscosities exhibited a bi-phasic progression, with the low viscosity bolus being the most heterogeneous and fragmented and the high viscosity bolus being the most homogenous and cohesive. Intraoral bolus cohesion was depicted in terms of the distributed velocity gradient, with higher gradients being associated with increased shear rate and bolus fragmentation. Lastly, we made a sensitivity analysis on tongue stiffness and contractility by varying the degree of extracellular matrix (ECM) stiffness through effects on the Mooney-Rivlin derived passive matrix and by varying maximum tetanized isometric stress, and observed that a graded increase of ECM stiffness was associated with reduced bolus spreading, posterior displacement, and surface velocity gradients, whereas a reduction of global contractility resulted in a graded reduction of obtainable accommodation volume, absent bolus spreading, and loss of posterior displacement. We portray a unidirectionally coupled solid-liquid FEM which associates myoarchitecture-based lingual deformation with intra-oral bolus flow, and deduce that local elevation of the velocity gradient correlates with bolus fragmentation, a precondition believed to be associated with aspiration vulnerability during oropharyngeal swallowing.

Strength Criterion of HTPB Composite Solid Propellant under Tension‐Shear Loading at Low Temperature

AbstractThe strength limits of composite solid propellants are different at different temperatures and loading states. To study the ultimate bearing capacity of Hydroxyl‐terminated polybutadiene (HTPB) propellant, the tensile‐shear loading fixture and propellant specimens were designed, and the tensile‐shear tests of HTPB propellant at different temperatures (223–298 K) and strain rates (0.01–1.00 s−1) were carried out. The variation of ultimate load of HTPB propellant with loading conditions was analysed. Based on the twin shear unified strength theory, the strength criterion of HTPB propellant under low temperature tension‐shear load was established, and the variation of mechanical parameters and stress limit surface with temperature and strain rate were analysed. The results show that the twin shear unified strength theory can be well applied to the strength analysis of propellants. The ultimate bearing capacity of HTPB propellant is the smallest near the loading angle of 45°. The shape of strength limit surface is an equilateral semi‐infinite hexahedron. With the decrease of temperature and the increase of shear rate, the strength limit surface of HTPB propellant expands outward.

Dewetting Dynamics of Sheared Thin Polymer Films: An Experimental Study.

An experimental investigation is reported on the effect of shear on the bursting of molten ultrathin polymer films embedded in an immiscible matrix. By use of an optical microscope coupled with a shearing hot stage, the dewetting dynamics, i.e., the growth of dewetting holes, is monitored over time at various shear rates. It is observed that their circularity is modified by shear and that for all temperatures and thicknesses studied the growth speed of the formed holes rapidly increases with increasing shear rate. A model balancing capillary forces and viscous dissipation while taking into account shear thinning is then proposed and captures the main features of the experimental data, such as the ellipsoid shape of the holes and the faster dynamics in the direction parallel to the shear. This research will help to understand the instabilities occurring during processing of layered polymeric structures, such as multilayer coextrusion.

Injectable laminin-biofunctionalized gellan gum hydrogels loaded with myoblasts for skeletal muscle regeneration

Moderate muscular injuries that exceed muscular tissue's auto-healing capacity are still a topic of noteworthy concern. Tissue engineering appeared as a promising therapeutic strategy capable of overcoming this unmet clinical need. To attain such goal, herein we propose an in situ-crosslinking gellan gum (GG)-based hydrogel tethered with a skeletal muscle-inspired laminin-derived peptide RKRLQVQLSIRTC(Q) and encapsulated with skeletal muscle cells (SMCs). Pre-hydrogel solutions presented decreasing shear viscosity with increasing shear rate and shear stress, and required low forces for extrusion, validating their injectability. The GGDVS hydrogel was functionalized with Q-peptide with 30% of efficiency. C2C12 were able to adhere to the developed hydrogel, remained living and spreading 7 days post-encapsulation. Q-peptide release studies indicated that 25% of the unbound peptide can be released from the hydrogels up to 7 days, dependent on the hydrogel formulation. Treatment of a chemically-induced muscular lesion in mice with an injection of C2C12-laden hydrogels improved myogenesis, primarily promoted by the C2C12. In accordance, a high density of myoblasts (α-SA+ and MYH7+) were localized in tissues treated with the C2C12 (alone or encapsulated in the hydrogel). α-SA protein levels were significantly increased 8 weeks post-treatment with C2C12-laden hydrogels and MHC protein levels were increased in all experimental groups 4 weeks post-treatment, in relation to the SHAM. Neovascularization and neoinnervation was also detected in the defects. Altogether, this study indicates that C2C12-laden hydrogels hold great potential for skeletal muscle regeneration. Statement of significanceWe developed an injectable gellan gum-based hydrogel for delivering C2C12 into localized myopathic model. The gellan gum was biofunctinalized with laminin-derived peptide to mimic the native muscular ECM. In addition, hydrogel was physically tuned to mimic the mechanical properties of native tissue. To the best of our knowledge, this formula was used for the first time under the context of skeletal muscle tissue regeneration. The injectability of the developed hydrogel provided non-invasive administration method, combined with a reliable microenvironment that can host C2C12 with nominal inflammation, indicated by the survival and adhesion of encapsulated cells post-injection. The treatment of skeletal muscle defect with the cell-laden hydrogel approach significantly enhanced the regeneration of localized muscular trauma.

Elevated shear rate-induced by exercise increases eNOS ser1177 but not PECAM-1 Tyr713 phosphorylation in human conduit artery endothelial cells

ABSTRACT Although evidence demonstrates the fundamental role of shear stress in vascular health, predominantly through the release of nitric oxide (NO), the mechanisms by which endothelial cells (EC)s sense and transduce shear are poorly understood. In cultured ECs tyrosine phosphorylation of PECAM-1 has been shown to activate eNOS in response to shear stress. However, in the human skeletal muscle microcirculation PECAM-1 was not activated in response to exercise or passive leg movement. Given this contradiction, this study aimed to assess the effect of exercise on conduit artery PECAM-1 and eNOS activation in humans. Eleven males were randomised to two groups; 30 min of handgrip exercise (n = 6), or a time-control group (n = 5). Protein content of eNOS and PECAM-1, alongside eNOS Ser1177 and PECAM-1 Tyr713 phosphorylation were assessed in ECs obtained from the radial artery pre- and post-intervention. Handgrip exercise resulted in a 5-fold increase in mean shear rate in the exercise group, with no change in the control group (group*time, P < 0.001). There was a 54% increase in eNOS Ser1177 phosphorylation in the exercise group, when compared to control group (group*time, P = 0.016), but no change was reported in PECAM-1 Tyr713 phosphorylation in either group (group*time, P > 0.05). eNOS and PECAM-1 protein content were unchanged (group*time, P > 0.05). Our data show that exercise-induced elevations in conduit artery shear rate increase eNOS Ser1177 phosphorylation but not PECAM-1 Tyr713 phosphorylation. This suggests PECAM-1 phosphorylation may not be involved in the vascular response to acute but prolonged elevations in exercise-induced shear rate in conduit arteries of healthy, active men.

Influence of freeze–thaw cycles and shear rate on sandstone-concrete interfacial bond strength: Experiment and degradation model

In the construction of tunnel engineering in cold regions, the good bonding between shotcrete and surrounding rock is the premise to ensure the stability of engineering support. However, the interface bonding between shotcrete and surrounding rock will be degraded by the freeze–thaw (F-T) cycles and the blasting vibration generated in the construction process of drilling and blasting method. Therefore, Firstly, the interfacial shear mechanical properties tests with different F-T cycles (i.e., 0, 5, 10, 15, and 20) and different shear rates (i.e., 0.25, 1.0, 2.0 and 4.0 mm/min) were carried out. Secondly, the effects of F-T cycles and shear rate on the variation of stress-displacement curve, the peak strength and interfacial failure mode of sandstone-concrete interface were analyzed. Finally, an interface degradation model for evaluating the effects of the above two factors was proposed. The primary conclusions are as follows: (1) With the increase of F-T cycles, the interfacial peak strength decreases gradually, while the adhesion area of sandstone on the concrete side increases gradually. The interfacial shear failure caused by F-T actions mostly occurs on the sandstone side. (2) With the increase of shear rate, the peak strength and the shear stiffness of sandstone-concrete interface increase gradually. The shear deformation of the interface is mainly reflected in the damage form of “abrasion, extrusion and shearing” between particles. (3) The greater the strength difference of rock materials on both sides, the side with weaker rock strength is the key area for interfacial F-T deterioration and debonding. (4) A new interface degradation model of rock-concrete interface shear strength considering F-T actions and shear rate was established, and the reliability of the theoretical model was verified. The study provides experimental and theoretical reference for exploring the interfacial debonding evolution mechanism of shotcrete in tunnels in cold regions.

Hydrothermal synthesis of boehmite nanorods from alumina sols

Boehmite nanorods (BNRs) were synthesized via the sol-gel process and hydrothermal method from alumina sols. Four influence factors, i.e. hydrothermal temperature and time, acetic acid contents, alcohol contents and stirring patterns, were explored to understand the reasons of BNRs growth. Scanning electron microscopy (SEM), transmission electron microscope (TEM), Fourier transform infrared (FT-IR) spectra and X-ray diffraction (XRD) were used to investigate the micromorphology, functional groups and phase composites of BNRs. The results show that the hydrothermal temperature and the contents of acetic acid play important parts in the one-dimension (1D) growth of BNRs. However, the hydrothermal time and the contents of alcohol have little effects. The growth mechanism of BNRs is related to the formation, growth and directional assembling of boehmite crystallites. After the simulation of dissipative particle dynamics (DPD), the increase of shear rate is beneficial to the 1D growth of BNRs.

Natural Antioxidant Extracted Waste Cooking Oil as Sustainable Biolubricant Formulation in Tribological and Rheological Applications.

Developing eco-friendly formulations using waste cooking oil as renewable biomass is of great interest and commercial importance in the fuels and lubricant industry. This manuscript reports novel study on preparing a biolubricant formulations as WCO-1, WCO-2 and WCO-3 by blending the curcumin extracted soybean waste cooking oil in three different compositions viz 10%, 20%, 30% v/v with the mineral base oil N-150. Curcumin was extracted as a natural antioxidant in 0.5 wt% waste cooking oil to inhibit thermal oxidation. This study comprises a detailed analysis in terms of tribological, rheological and thermophysical characteristics such as viscosity, viscosity index, pour point and flash point parameters of the biolubricant by standard ASTM methods. Further, tribological and rheological analysis was done by the four-ball wear tester and Anton Paar, MCR-72, respectively. The thermophysical evaluation of WCO formulated biolubricant has shown excellent properties. The viscosity index of the formulated biolubricant increases with an increase in the concentration of waste cooking oil. In contrast, the pour point has also been depressing at lower temperature conditions. Thus, WCO based biolubricant was found to be more effective at extreme temperature conditions than the mineral base oil (N-150). Rheological studies have indicated the non-Newtonian behaviour of the biolubricant with an increase in shear rate. Whereas, tribological analysis demonstrates that wear scar diameter has significantly reduced from 0.685 to 0.573 mm, and the coefficient of friction decreased from 0.117 to 0.080 with respect to the mineral base oil. Thus, a straightforward green approach has been discovered by directly utilizing waste cooking oil for biolubricant formulation.Graphical abstract

Effect of lubricant shear thinning behaviour on major functioning parameters of a pad bearing operating in hydrodynamic lubrication region

Type of lubricant used for fluid film bearings is one of the most important factors to consider. Bearing characteristics have to maintain steady throughout a wide range of conditions. However, viscosity, which is one of the primary lubricant properties, highly deviates depending on environmental and operational conditions. Macro-molecular micro-structure of lubricants is strongly correlated to temperature and shear rate, leading to a shear thinning behaviour. This work aims in studying a pad bearing lubricated by a shear thinning oil in hydrodynamic region. Hydrodynamic wedge was modelled for a small fixed pad bearing of 8.5 mm inner radius, 14.5 mm outer radius, 40° angle and 50 μm inlet – outlet film thickness difference. Variety of cases were studied for several runner rotational velocities and minimum film thickness. Lubricant was modelled as a carreau fluid. Load carrying capacity, power losses, friction coefficient, mass flow rate, temperature and viscosity were evaluated. From the aspect of load carrying capacity, this specific pad bearing is optimally operating for rotational velocities of up to 100 krpm. Above this threshold, viscosity highly downgrades due to increase in temperature and shear rate, causing a negative impact in load capacity. Shear thinning behaviour of lubricants is of high importance and should not be considered negligible.

The effect of Bruton's tyrosine kinase inhibitor ibrutinib on atherothrombus formation under stenotic flow conditions

BackgroundBruton's kinase (Btk) is critical for collagen-triggered platelet signal transduction. The Btk inhibitor ibrutinib has been shown to selectively block platelet adhesion to atherosclerotic plaque material under laminar arterial flow. However, this has not been studied under a shear gradient, which is characteristic for atherothrombosis. ObjectiveTo determine the effect of ibrutinib treatment on in vitro thrombus formation on collagen and atherosclerotic plaque material in the absence or presence of a shear gradient. MethodsBlood was obtained from patients with chronic lymphocytic leukemia, mantle-cell lymphoma and Waldenström macroglobulinemia with and without ibrutinib treatment and perfused through a microfluidic channel with(out) 60% stenosis over Horm type I collagen or human atherosclerotic plaque homogenate. ResultsAt a constant shear rate of 1500 s−1, platelet deposition was significantly decreased in blood from haematological malignancy patients treated with ibrutinib as compared to untreated patients, on atherosclerotic plaque material but not on collagen. However, thrombus size, stability, and height, were reduced on both plaque material and collagen. An increase in shear rate up to 3900 s−1, as induced by 60% stenosis, resulted in decreased platelet deposition and thrombus parameters on plaque material but not on collagen when compared to a laminar shear of 1500 s−1. Ibrutinib treatment decreased platelet deposition and thrombus parameters even further around the stenosis. ConclusionTreatment of patients with haematological disorders with the Btk inhibitor ibrutinib reduces in vitro platelet deposition, thrombus size and contraction on human atherosclerotic plaque around a stenosis when compared to patients not receiving ibrutinib.

Effect of Solid Volume Concentration on Rheological Properties of Chengdu Clay Slurry

The determination of rheological model about the debris flow is the basis of the simulation of mud flow impact distance and sedimentary fan. By using a mcr301 rheometer, rheological experiments of Chengdu clay slurry with different solid volume concentrations were carried out and the effect of solid volume concentration on shear stress were analyzed. Then the rheological process of Chengdu clay slurry with different solid volume concentration was fitted on the basis of the power law model, the Bingham model and the H–B model. The conclusions are drawn as follows: Chengdu clay mud is a typical shear-thinning non-Newtonian body. The influence of solid concentration on the flow curve is different. When the solid volume concentration is not less than 34% and the shear rate is less than 1.0 s−1, the shear stress increases rapidly as the shear rate increases. Meanwhile, when the shear rate is greater than 1.0 s−1 the shear stress decreases with the increase in the shear rate. When the solid volume concentration is less than 31.6% and the shear rate is less than 1.0 s−1, the shear stress increases with the increase in the shear rate, while when the shear rate is more than 1.0 s−1, the shear stress is less affected by shear rate. In the range of low shear rate (less than 1.0 s−1), the increase amplitude of shear stress (slope of semi logarithmic coordinate flow curve) increases as the solid volume content increases. The flow curve of Chengdu clay mud can be reflected in the whole process by using the Herschel and Bulkley model. It is the best mathematical model to fit the rheological process of Chengdu clay mud. According to the above results, the effect of solid volume concentration on the yield stress of the H–B model is analyzed.

Formulation and production of persimmon milk drink and evaluation of its physicochemical, rheological, and sensorial properties.

One of the effective ways for increasing milk intake in a diet is producing flavored milk. In the present study, flavored persimmon milk drinks were formulated and produced. Rheological, sensorial, and physicochemical properties of the drinks were evaluated. Different amounts of persimmon (5, 10, 20, and 30% W/V), gum Arabic (0.1 and 0.2% W/V), and sugar (3 and 5% W/V) were used to produce persimmon milk. All the experiments were done in a completely randomized design (CRD) in three replicates. First, persimmons were mixed thoroughly in a blender then, according to the formulation, whole milk was added to it and mixed again. The obtained mixture was heated up to 50 ᵒC then sugar and the gum were added and mixed completely for 3 min. The drink was pasteurized at 90 ᵒC for 1 min. Sensorial analysis revealed that the most acceptable persimmon milk was related to 0.1% gum Arabic, 5% sugar, and 10% persimmon. Flow behavior of the drinks with 20 and 30% persimmon was Non‐Newtonian, while 10% persimmon samples with and without gum showed Newtonian behavior. The drinks with 20 and 30% persimmon were pseudoplastic, and their apparent viscosity increased by increasing shear rates. By applying a proper content of persimmon in milk, we can produce a nutritious flavored milk drink with acceptable taste, stability, and consistency. As this drink has high nutrient contents like phenol, dietary fiber, vitamins, antioxidants, etc., it can help promote health, especially for children.

Physical-chemical characteristics of “Red Meal”, a novel non-defatted additive in the fish feed from cracked biomass of Haematococcus pluvialis

Haematococcus pluvialis (HP) astaxanthin is widely used in the aquaculture industry to improve the pigmentation of salmon, shrimp, and egg yolk, also this pigment has an important physiological role in animal health and reproduction. The “Red Meal” (RM) is the whole cracked biomass of HP homogenized in vegetable oil to form a non-defatted meal product. This study aimed to determine the physical and chemical characterization of a novel non-defatted meal feed product (“Red Meal”, so-called by the production company). RM behavior was shear-thickening fluid at 40 °C, whereas, at 5, 10, 25, 30, and 60 °C shear-thinning fluid was observed; thus, viscosity was decreased with the increase of shear rate. On the other hand, the RM presented a 14.5 ± 0.1, 62.5 ± 9.6, 17.6 ± 2.7, 3.7 ± 0.1, and 1.5 ± 0.4% of protein, lipids, carbohydrates, ash, and moisture, respectively. The fatty acid profile of RM was 51.1% of linoleic acid C18:2(c9c12), 25.4% of oleic acid C18:1(c9), 9.5% of palmitic acid C16:0, 7.9% of heneicosylic acid C21:1%, and 2.8% of stearic acid C18:0, where the linoleic acid and oleic acid represented 76.5% of the total fatty acid profile. Additionally, the most abundant polyunsaturated fatty acid was ω-6 (51.40%), followed by ω-9 (25.40%); whereas a small amount of omega-3 (0.88%) was reported. The total carotenoid content in the RM was 17.19 mg/g of dry biomass; in which the main pigment was astaxanthin esters (55.13%), followed by lutein (5.67%), free astaxanthin (5.54%), β-carotene (2.76%), and canthaxanthin (2.65%).

Reduced and increased flow resistance in shear-dominated flows of Oldroyd-B fluids

We present a comprehensive analytical and numerical study of shear-dominated flows of Oldroyd-B fluids. Starting from transient ideal Couette flow, we show that less work is required to increase the shear rate than to decrease it. Generalizing this observation to non-homogeneous steady flows, we show that reduced flow resistance is present around streamlines with increasing shear rate and increased flow resistance is present around streamlines with decreasing shear rate. We demonstrate this effect in smoothly converging or diverging Couette and Poiseuille flows. Finally, we show that the reduced flow resistance observed in the flow past a cylinder in a straight channel is caused by the contraction-expansion-like flow that takes place at the sides of the cylinder. Our findings are validated by a wide parametric analysis regarding the geometrical characteristics of the flow domains and the material parameters of the Oldroyd-B model. • Shear-thinning and shear-thickening effects can be predicted by the Oldroyd-B model. • Reduced flow resistance is present along streamlines with increasing shear rate. • Increased flow resistance is present along streamlines with decreasing shear rate. • The variations in pressure drop and drag force in viscoelastic flows are explained.

Print fidelity evaluation of PVA hydrogel using computational fluid dynamics for extrusion dependent 3D printing

This study presents a practical method of print fidelity evaluation for an extrusion-dependent technique of 3D printing. Simulation through computational fluid dynamics (CFD) tool has been used for evaluating the fidelity of printing. The polyvinyl alcohol (PVA) based hydrogel was prepared with deionized (DI) water and PVA powder using a magnetic stirrer at 90 °C for 3D printing. Rheological tests were carried out for checking the viscosity at various shear rates. CFD simulation was done by employing the Bird-Carreau modelusing rheological values. Velocity, pressure, shearing rate, and viscosity distributions through nozzle were obtained. From the shear rate and viscosity results, the increase in shear rate and decrease in gel’s viscosity for both the nozzles prove that the material can be extruded. It was seen that the nozzle with a diameter of 0.51mm shows better results than the 0.41mm diameter, which was concluded from the values of maximum shear rate at the edges of the nozzles. The maximum shear rate value has reached a maximum of up to 326.5102s –1 whereas for a 0.41 mm diameter nozzle, it is 623.8037s –1 increasing the chances of developing wavy edges in a 0.41mm diameter nozzle than a 0.51mm diameter nozzle concluding that the nozzle with 0.51mm diameter gives far better results than the 0.41mm diameter nozzle.

Simulation and experimental investigation of dielectric and magnetic nanofluids in reduction of oil viscosity in reservoir sandstone

High demand in the reduction of viscosity of heavy oil from reservoir sandstone has been a great interest with the applications of electromagnetic (EM) assisted for the enhanced oil recovery. Therefore, the conversion of EM waves properties into the reservoir region must be taken into consideration and the interaction between the reservoir fluids and the solid phases. In this study, the rheological and adsorption effect of Fe 3 O 4 , ZnO, Al 2 O 3, SiO 2, and CuO at high temperature and pressure on reservoir sandstone have been simulated using Biovia material studio and experimentally investigated with the effect of electromagnetic waves. The measurement of the viscosity are at a different shear rate for dielectric and magnetic nanofluids. The viscosity of the crude oil varies over a range of shear rates (100–2000 s −1 ) and temperatures (25–120 °C), the crude oil exhibited extremely high viscosity at a low shear rate and low temperature, and gradually drifts to lower viscosity at the reservoir conditions (2000 s −1 - 119 °C). It was revealed from the result that Fe 3 O 4 Nanofluid exhibits better performance compares to ZnO, and Al 2 O 3 at a high shear rate (2000, 1500, and 1000 s −1 ) at reservoir condition. Nanofluid shows Newtonian behavior with an increase in shear rate and the viscosity of the oil decrease with an increase in temperature. As the dispersion of the particles increases, the interactions between the components of sandstone crude Oil and nanoparticles also increased, that favors viscosity reduction which in turn increase the fluid mobility. • The mechanism behind the viscosity reduction caused by Nanofluid is explained. • Different Nanofluid (Fe 3 O 4 , ZnO, Al 2 O 3 , SiO 2 , and CuO) at high temperature and high pressure were investigated. • Oil recovery prediction using Multiple linear regression model are explained. • Modelling of reservoir properties using geo-electric and petrophysical properties were estimated.

Modeling of viscosity of unstable crude oil–water mixture by characterization of energy consumption and crude oil physical properties

When oilfield development enters the middle and late stages, the crude oil–water mixture (COWM) produced from oil wells often has a high water cut and cannot form a stable emulsion. The traditional viscosity model of an emulsion is not suitable for this unstable mixture. Mastering the viscosity characteristics of the unstable crude oil–water mixture with high water cut (UCMH) for pipeline transportation of such mixtures is important. The apparent viscosities of UCMH (water cut of mixture ranging from 0.70 to 0.90) for 16 crude oils were determined via the stirring viscometric method. The results showed that the apparent viscosity of UCMH decreased with increasing shear rate, water cut of mixture, and temperature, demonstrating the property of shear thinning. The apparent viscosity of UCMH did not depend on the content of single surfactants such as resins, asphaltenes, waxes, and mechanical impurities but was closely related to the content of the above-mentioned combinatorial surfactants. The parameter exergy loss rate of shear that describes energy consumption was determined to characterize the external shear action on UCMH, which can fully reflect the essence of the mechanical energy consumption in the emulsifying process under different shearing conditions. A new viscosity model for UCMH was established by the quantitative characterization of the energy consumption and crude oil physical properties (i.e., saturate content, aromatic content, surfactant content, acid value, and crude oil viscosity). In light of the statistical results of 336 groups of validation experimental data from four crude oils, the average relative deviation between the apparent viscosity calculated by the new model and the measured apparent viscosity of UCMH was 5.3%, which is considerably better than the traditional emulsion viscosity models, that is, the Einstein, Vand, Taylor, and Richardson models.

Flow-induced crystallization of polylactides

In this work, the flow-induced crystallization of two polylactides (PLAs) with different microstructures (different l-lactic acid contents) is studied using simple shear, uniaxial extension and capillary flow experiments. In a simple shear and capillary flow, an increase in shear rate and a decrease in temperature were found to enhance the crystallization kinetics particularly for Weissenberg numbers (based on the reptation relaxation time, Wi) greater than 1 (strong flow causing chain stretching). On the other hand, in a uniaxial extensional flow, once a critical Hencky strain is achieved, crystallization starts independently of strain rate and temperature. The amount of mechanical work per unit volume imposed/dissipated onto the polymers during flow to initialize crystallization was also calculated in the simple shear, capillary, and extensional flow. The critical mechanical work for the onset of flow-induced crystallization was found to be independent of temperature and degree of molecular chain stretch (Wi) as Wi becomes greater than 1. The critical mechanical work for the onset of flow-induced crystallization in an extensional flow was found to be much smaller than that in a shear flow. The PLA sample with higher content of PLLA showed slightly higher zero-shear viscosity and a smaller thermodynamic barrier for the onset of crystallization. Finally, the degree of crystallinity increases linearly from 0% at the start of the flow-induced crystallization region and reaches a plateau at Wi equals to around 1.

Stability and Deformation of Vesicles in a Cylindrical Flow.

In this work, we used dissipative particle dynamics to study the stability, deformation, and rupture of polymer vesicles confined in cylindrical channels under the flow field. The morphological evolution, elongation, and rupture of vesicles and the corresponding mechanisms were intensively investigated. Bullet-like vesicles, leaking vesicles, spherical micelles, hamburger-like micelles, and bilayers were observed by changing the degree of confinement and dimensionless shear rate. We found that increasing the dimensionless shear rate and the degree of confinement can cause the deformation or rupture of polymeric vesicles. The asphericity parameter was utilized to describe the degree of elongation of vesicles deviating from the sphere in the direction of the flow. The results show that the aggregates are more likely to be spherical when the confinement is weak, while they become elongated bullet-like shapes when the confinement is strong. The investigation of dynamics reveals that the degree of confinement and the dimensionless shear rate can affect the chain stretching and reorganization during the process of vesicle elongation. Furthermore, the rupture time of the vesicle shows a nonlinear decrease with an increase in the dimensionless shear rate, and the confinement also contributes to the rupture. The results are very useful for guiding the application of vesicles in a flow environment.