Rheological Properties Of Fluid Research Articles

Exploring double-diffusive nanofluid flow in divergent/convergent nondarcy porous space: A machine learning numerical approach with zero mass flux

In this study, authors address the problem of analyzing the Jeffrey–Hamel nanofluid flow within a nonparallel channel under the influence of a thermally balanced non-Darcy permeable medium. Our objective is to explore the behavior of the nanofluid, employing the Buongiorno nanofluid model, and considering factors such as zero mass flux conditions, variable rheological fluid properties, and the presence of temperature jump phenomena through ANN-PSO-NNA. To tackle this intricate issue, propose a novel approach using Artificial Neural Networks (ANN) integrated with particle swarm optimization (PSO) hybrid with neural network algorithm (NNA). This combined technique is referred to as ANN-PSO-NNA. The governing flow equations based on the Jeffrey–Hamel analysis are first transformed into dimensionless forms. To establish the efficacy of our approach compare it with the widely used NDSolve method. Furthermore, the study presents the absolute error analysis for four distinct cases offering a quantitative assessment of the accuracy of ANN-PSO-NNA. The absolute error between the NDsolve and the proposed ANN-PSO-NNA is given for four different cases, ranging from 1.95E-06 to 1.18E-08. The biases and weights obtained through proposed method range from −10 to 10. This enables us to gauge the performance of the ANN-PSO-NNA minimum values of the fitness function 2.37E-08, 2.30E-08, 3.92E-08, and 1.22E-08 from multiple independent runs, which are showcased to be convergent, underscoring the robustness of the ANN-PSO-NNA approach. Employing graphical representations, explores the influence of various parameters on the velocity and temperature profiles. Our integrated approach offers a comprehensive understanding of the underlying dynamics, paving the way for optimized designs and enhanced efficiency across these diverse engineering applications.

Bingham plastic fluids flow analysis in multimembranes fitted porous medium

A mathematical analysis is presented for the flow of a Bingham plastic fluid propelled by a multi-membrane pumping mechanism through porous media. Two successive membranes with different amplitude, diameter, and phase lag, are fitted at the upper wall of the channel and the lower wall is stationary. Due to the simultaneous propagation of both membranes, the pressure is generated at the membrane position, which helps in propelling the fluids in forward and backward directions depending upon the contraction and expansion cycle of the membranes. The low Reynolds number assumption and lubrication theory are utilized to linearize the governing equations which are further analytically derived by finding the complementary function and particular integral and then employing MATLAB codes to compute the illustrations for the interpretation of the results. The effects of key parameters like plug flow region, pore size and diameter of membranes on the velocity field, wall shear stress, pressure gradient, fanning friction factor, head loss and particle trajectories, are analysed in the microchannel. Results of the present model conclude that the geometrical properties of membranes, rheological properties of fluids and porosity of the medium significantly alter the flow and pumping characteristics which give valuable insights for the design of micro-valve less pumping actuators aimed at controlling microscale transport processes in various medical diagnoses and treatments.

Influence of rheological parameters on the performance of the aerated coaxial mixer containing a pseudoplastic fluid

Gas dispersion in non-Newtonian fluids has numerous applications in many chemical and biochemical applications. However, the effect of the power-law model constants describing the rheological behavior of the pseudoplastic fluid has never been investigated. Thus, a numerical model was developed to simulate the hydrodynamics of gas dispersion in non-Newtonian fluids with a coaxial mixer. Then, a set of experiments was conducted to assess the mass transfer efficacy of a coaxial mixer to benchmark the numerical model. In this regard, various methods, including dynamic gassing-in and electrical resistance tomography methods, were used to quantify the mass transfer and gas hold-up profiles. The influence of fluid rheological properties, gas flow number, and rotating mode on the power consumption, mass transfer coefficient, bubble size profile, and hydrodynamics were examined both experimentally and numerically. The response surface model (RSM) was employed to explore the individual effects of power-law model constants on mass transfer. The RSM model utilized five levels for the consistency index (k), five levels for the flow index (n), and three levels for the gas flow number. The statistical model proposed that the absolute model constants for the flow and consistency indices were 0.0012 and 0.0010, respectively, for the co-rotating mixer. Conversely, for the counter-rotating mixer, these constants were 0.0010 and 0.0013, respectively. Therefore, this study revealed that the co-rotating coaxial mixer was well-suited for dispersing gas within a fluid with high consistency. In contrast, the counter-rotating mixer proved effective in enhancing gas dispersion within a fluid with a lower flow index.

Study of Lactobacillus plantarum coated with Tremella polysaccharides to improve its intestinal adhesion.

The adhesion of probiotics to the intestine is crucial for their probiotic function. In previous studies, Tremella polysaccharides (TPS) (with sodium casein) have shown the potential to encapsulate probiotics and protect them in a simulated gastrointestinal tract. This study explored the effect of TPS (with sodium casein) on the adhesion of probiotics. Lactobacillus plantarum was coated with TPS and sodium casein in different proportions, and was freeze-dried. The rheological properties of the mixture of probiotics powder and mucin solution were determined by static and dynamic rheological analysis. Aqueous solutions of probiotic powder and mucin mixture exhibited pseudoplastic fluid rheological properties. The higher the proportion of TPS content, the higher the apparent viscosity and yield stress. The mixed bacterial powder and mucin fluid displayed thixotropy and was in accordance with the Herschel-Bulkley model. The TPS increased the bio-adhesive force of the probiotic powder and mucin. When using TPS as the only carbon source, the adhesion of L. plantarum to Caco-2 cells increased by 228% in comparison with glucose in vitro. Twelve adhesive proteins were also detected in the whole-cell proteome of L. plantarum. Among them, ten adhesive proteins occurred abundantly when grown with TPS as a carbon source. Tremella polysaccharides therefore possess probiotic properties and can promote the intestinal adhesion of L. plantarum. © 2024 Society of Chemical Industry.

The Effects of Organically Modified Lithium Magnesium Silicate on the Rheological Properties of Water-Based Drilling Fluids.

To address the problem of insufficient temperature and salt resistance of existing polymer viscosity enhancers, we designed an organic-inorganic hybrid composite as a viscosity enhancer for water-based drilling fluids, named LAZ, and it was prepared by combining a water-soluble monomer and lithium magnesium silicate (LMS) using an intercalation polymerization method. The composite LAZ was characterized using Fourier transform infrared spectroscopy, transformed target X-ray diffractometry, scanning electron microscopy, and thermogravimetric analysis. The rheological properties of the composite LAZ were evaluated. The composite LAZ was used as a water-based drilling fluid viscosity enhancer, and the temperature and salt resistance of the drilling fluid were evaluated. The results showed that the composite LAZ presented a complex reticulation structure in an aqueous solution. This reticulation structure intertwined with each other exhibited viscosity-enhancing properties, which can enhance the suspension properties of water-based drilling fluids. The aqueous solution of the composite LAZ has shear dilution properties. As shear rate increases, shear stress becomes larger. The yield stress value of the aqueous solution increases as the composite LAZ's concentration increases. The aqueous solution of the composite LAZ exhibits strong elastic characteristics with weak gel properties. The addition of the composite LAZ to 4% sodium bentonite-based slurry significantly increased the apparent viscosity and dynamic shear of the drilling fluid. The drilling fluids containing the composite LAZ had good temperature resistance at 150 °C and below. The rheological properties of brine drilling fluids containing the composite LAZ changed slightly before and after high-temperature aging at 150 °C.

Investigating the efficacy of novel organoclay as a rheological additive for enhancing the performance of oil-based drilling fluids

Oil-based drilling fluids (OBDFs) are extensively used in the drilling industry due to their superior performance in challenging drilling conditions. These fluids control wellbore stability, lubricate the drill bit, and transport drill cuttings to the surface. One important component of oil-based drilling fluids is the viscosifier, which provides rheological properties to enhance drilling operations. This study evaluates the effectiveness of Claytone-IMG 400, a novel rheological agent, in enhancing the performance of OBDFs under high-pressure and high-temperature (HPHT) conditions. A comparative analysis was conducted with a pre-existing organoclay (OC) to assess the improvements achieved by Claytone-IMG 400. The OCs were analyzed using X-ray diffraction (XRD), X-ray fluorescence (XRF), scanning electron microscopy (SEM), and particle size distribution (PSD) to identify their mineral and chemical compositions, morphologies, and particle sizes. The drilling fluid density, electrical stability, sagging tendency, rheological properties, viscoelastic properties, and filtration properties were studied to formulate a stable and high-performance drilling fluid. The results confirmed that the novel OC does not affect the drilling fluid density but enhances the emulsion stability with a 9% increment compared with the drilling fluid formulated with MC-TONE. The sagging experiments showed that Claytone-IMG 400 prevented the sagging issues in both static and dynamic conditions. Also, Claytone-IMG 400 improved the plastic viscosity (PV), yield point (YP), and apparent viscosity (AV). The PV, YP, and AV were improved by 30%, 38%, and 33% increments respectively compared with the drilling fluid formulated with MC-TONE. The YP/PV ratio increased with a 6% increment from 1.12 to 1.19. Moreover, the gel strength (GS) was significantly increased, and the filtration properties were enhanced. The filtration volume was reduced by 10% from 5.0 to 4.5 cm3, and the filter cake thickness had a 37.5% reduction from 2.60 to 1.89 mm. The novelty of this study is highlighted by the introduction and evaluation of Claytone-IMG 400 as a new rheological additive for safe, efficient, and cost-effective drilling operations. The results indicate that Claytone-IMG 400 significantly improves the stability and performance of OBDFs, thereby reducing wellbore instability and drilling-related problems.

Towards Semi-Solid Organic Redox Flow Batteries: Material Screening, Electrochemical Performance, and Reactor Design Optimization

As our society transitions to cleaner sources of energy, the need for stationary electricity storage becomes increasingly important. In this context, redox flow batteries (RFBs) have emerged as a promising solution to provide electricity storage at full scale, due to their high scalability and flexibility. However, despite the growing research interest, there is still a urgent need of novel batteries, which are able to operate at high energy densities while relying on sustainable, abundant, and cost-effective electrolytes.In this work we report the development of novel semi-solid RFBs based on cost-effective and environmentally friendly organic materials. We have systematically screened different classes of organic molecules, to identify suitable redox couples that can operate under stable conditions (i.e., >5,000 cycles) in a wide pH range. Therefore, we have experimentally investigated the most promising redox couples in a 10-cm2 electrochemical cell, to understand the behavior of the systems under different carbon and active molecule loadings. Finally, we have simulated the performance of the battery under dynamic and steady-state conditions, aiming to quantify the influence of fluid dynamics and rheological properties of the carbon slurry on the electrochemical performance. Based on our simulations results, we have identified new reactor designs for the RFB, aiming to optimize both fluid dynamics and electrochemical performance of the battery. Such designs represent an important first step towards future upscaling strategies.

Experimental Investigations on Thermophysical, Tribological and Rheological Properties of MoS2 and WS2 Based Nanolubricants with Castor Oil as Base Lubricant

Molybdenum disulfide (MoS2) and Tungsten disulfide (WS2) nanoparticles addition to castor oil produce nano lubricants of novel properties. These nanomaterial additives are dispersed thoroughly in the liquid phase and are intended to boost the base fluid's thermo-physical, rheological, and tribological properties. All these properties have been studied by varying concentrations of nanoparticles from 0.05 to 2.5%. The size of both nanoparticles are in the range of <20nm. The density of nano lubricants was found to change with respect to nanoparticle concentration and temperature. The density increases from 0.06 to 0.6% with respect to the increase in concentration and decreases by 4%, for increasing temperature from 25 to 100 o C. A significant (15 %) increase in thermal conductivity with MoS2 nanoparticles in lubricants could be observed while with WS2 nanoparticles only 8 % enhancement was observed. The rheological study suggests that nano lubricants have better dynamic viscosity and shear stress than neat castor oil. A tribology study showed improved lubrication properties of the nanolubricants as compared with base castor oil. The addition of MoS2 and WS2 nanoparticles in castor oil decreased the friction coefficient by 53 % and 42 %, respectively, and reduced the wear scar diameter by 24% and 20 %, respectively, as compared to base castor oil. This study was done to develop nonedible vegetable oil based nanolubricants exploring their potential as emerging lubricants.

Particle-wall hydrodynamic effects on optical trapping viscometry

Optical tweezers are a versatile setup used to measure forces in soft materials and characterize the rheological properties of fluids and gels. An accurate measurement of these forces is complicated by the interaction between the optically trapped materials and nearby substrate walls. This work presents a comprehensive Brownian Dynamic (BD) model that accounts for the hydrodynamic interactions between an optically trapped particle and a nearby boundary. The model is based on a midpoint algorithm, which simplifies accounting for diffusion gradients that arise from hydrodynamic interactions. Experiments using an optical tweezer and a quadrant position detector (QPD) are performed to validate these experiments. We conduct experiments by varying input laser current from 100 mA to 300 mA. Our experiments show that measured viscosity at 100 mA is ∼19% higher than the value expected for room temperature water (0.89 mPa-s). The discrepancy diminishes to 4% when a 300 mA current is used. Simulations performed with the BD model show that, for a nominal spring constant of ks=4.332×10−4IlaserpN/μm, the discrepancy can be explained via hydrodynamic interactions that influence the measured effective viscosity. Wide variability in confidence interactions observed in our data can be replicated by using a range of diameters in our simulation. This is consistent with DLS measurements of the particles used in this study, which show that the mean diameter was (1.63 ± 0.28) μm. This work has implications for measuring Newtonian media viscosities up to ∼63 mPa-s, as determined by a scaling analysis of limitations for our measurement system.

High efficiency regulating sedimentation and rheological properties of copper tailings using polycarboxylate superplasticizers

The recovery of low grade and fine particle copper ore usually requires sufficient dissociation, which reduces the particle size to the submicron level, presenting new challenges in subsequent copper tailings disposal. Flocculants can improve tailings sedimentation efficiency, but they also change the rheological properties of the slurry, resulting in low efficiency and high energy consumption during long-distances pumping. To address this issue, this study introduced polycarboxylate ether (PCE) superplasticizers as auxiliary additives for tailings treatment to improve fine particles sedimentation efficiency while enhancing slurry flowability. The results showed that compared to non-ionic polyacrylamide (NPAM) treated slurries, the synergistic effects of PCE and NPAM increased the initial sedimentation rate (ISR) by up to 3.4 times while decreasing the yield stress by up to 8 times and the thixotropic loop area by 10.5 times. DLVO theory calculations showed that PCE mainly affects particle interactions through a significant decrease in electrostatic repulsion. By in-situ monitoring with a focused beam reflectance measurement (FBRM) device, it was demonstrated that the synergistic effect of PCE improved the flocculation ability, strength, and regrowth ability of flocs. Furthermore, strong correlations were found between floc properties and fluid rheological properties. Overall, this study indicated that PCE additive was a promising reagent for fine particles slurry rapid settling and flowability enhancement, providing a new approach for copper tailings disposal.

Longitudinal wave propagation in an elastic cylinder embedded in a viscoelastic fluid

Abstract A novel analytical investigation of longitudinal wave propagation in an elastic cylinder embedded in a viscoelastic fluid is proposed. The Maxwell model is used to describe the viscoelastic fluid behavior. With appropriate boundary conditions, a complex dispersion equation of longitudinal wave has been established. The aim of this paper is to study the effect of the fluid rheological properties on the longitudinal wave characteristics (attenuation and velocity). It is shown that the attenuation is the sum of a viscous and non viscous component. The viscosity induced attenuation is predominant at low frequencies. On the other hand, the effect of the liquid amount and elastic cylinder radius on the attenuation and velocity are studied. A critical normalized liquid thickness is highlighted. Beyond this critical value, the influence of the outer boundary condition can be neglected. At last, among other interesting phenomena, it is highlighted that if the Deborah number increases, the attenuation decreases. This variation characterize a stiffening of the viscoelastic medium. In addition, the obtained results show that the viscosity measurement should be performed at low frequencies using small elastic cylinder radius. Accordingly, these investigations are novel and can be applied in geophysics, food industry, medicine, non-destructive testing of materials, design and development of fluid sensors.

Soy protein isolate-guar gum-goose liver oil O/W Pickering emulsions that remain stable under accelerated oxidation at high temperatures.

Goose liver oil (GLO) is a solid-liquid mixture, rich in polyunsaturated fatty acids and high in nutritional value, but poor in fluidity and easily oxidized. Therefore, oil-in-water (O/W) Pickering emulsions of three polysaccharides and soy protein isolate (SPI) with GLO were prepared to improve the stability of it. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), Fourier-transform infrared spectroscopy, and zeta potential revealed that the SPI and complexes with konjac glucomannan, pectin, and guar gum (GG) ranged from 17 to 75 kDa, with the site of action being the -OH stretch and the amide group, and bound by hydrogen bonding. Adding konjac glucomannan and GG significantly increased the water contact angle of the SPI to 74.1° and 59.0°, respectively. Therefore, the protein-polysaccharide complexes could enhance the emulsion stability. In addition, the O/W Pickering emulsions with GLO had near-Newtonian fluid rheological properties with a significant increase in apparent viscosity and viscoelasticity, forming a dual network structure consisting of a ductile and flexible protein network and a rigid and brittle polysaccharide network. The microstructure observation indicated that the O/W emulsions were spherical and homogeneous. The highest emulsification activity was observed for the SPI-GG-GLO emulsions, without significant delamination or flocculation and high oxidative stability after 7 days in storage. These results demonstrate that the construction of SPI-GG-GLO O/W Pickering emulsions can stabilize GLO even at high temperatures that promote oxidation. © 2023 Society of Chemical Industry.

A New Approach for Predicting the Rheological Properties of Oil-Based Drilling Fluids under High Temperature and High Pressure Based on a Parameter-Free Method

Under different temperatures and pressures, the physical parameters of drilling fluid will change, resulting in inaccurate drilling hydraulic calculations. Aiming to address the problem of the traditional rheological prediction method needing to first determine the rheological model, this paper proposed a method for first predicting the readings of the rheometer and then determining the rheological model. The model established in this paper adopted a parameter-free method, which expands the application range of the model. Rheology experiments were carried out on the three types of oil-based drilling fluids collected at the well site. The model in this paper was verified based on the experimental data. The results showed that, compared with the traditional drilling fluid rheological prediction method, the model established in this paper had a better prediction effect, with an average error of 4.85%, and the average error reduction ranges from 3.8% to 8.3%. The model established in this paper is able to provide theoretical support for accurate hydraulic calculation.

Dynamics of drop formation and characterization of additive manufactured CS/AgNP/PVA composite membranes

AbstractThis study investigated the dynamics of drop formation and the printability of chitosan/silver nanoparticles composite fluid (CS/AgNP) modified with polyvinyl alcohol (PVA) using an inkjet 3D printer. It specifically investigated the relationship between rheological properties and fluid mechanical properties in determining the minimum drop velocity for 3D printing of modified CS ink. Proper matching of modified CS fluid rheological properties to the established physical parameters generated adequate droplets on glass substrates and formed membrane composites. The dynamic viscosity of the CS ink decreased with an increase in the concentration of PVA, which resulted in the disruption of existing molecular forces within the CS/AgNP polymer chains, suggesting that the solvent (PVA) was responsible for reducing the shear stress, surface tension, and viscosity of the composite membranes and subsequently improving the flow rates of the CS matrix at the nozzle orifice. Optimized drop velocity of 1.77 m/s yielded adequate formation of the CS/AgNP/PVA membrane composite with enhanced surface morphology, while an increase in drop velocity to 2.5 m/s brought about the formation of satellite droplets with irregular surface structures in printed CS composites. Therefore, adherence to minimum fluid drop velocity is fundamental to effective inkjet printing of composite membranes.

Effect of Nanoparticles on Rheological Properties of Water-Based Drilling Fluid.

Nano-water-based drilling fluids (NWBDFs) are prepared using nano-copper oxide (CuO) and multiwalled carbon nanotubes (MWCNTs) as modification materials. The effects of the temperature and concentration of the nanoparticles (NPs) on the rheological properties are studied using a rotational rheometer and viscometer. Also, the influence of two NPs on the filtration properties is studied using a low-pressure and low-temperature filtration apparatus, as well as a scanning electron microscope (SEM). It is found that MWCNTs with a concentration of 0.05 w/v% have the most obvious influence on the NWBDFs, which improve the stability of the gel structure against temperature and also decrease the filtration rate. Finally, a theoretical model predicating the yield point (YP) and the plastic viscosity (PV) as a function of the temperature considering the influence of the NPs is developed based on DLVO theory.

A Novel Model for the Real-Time Evaluation of Hole-Cleaning Conditions with Case Studies

The main challenge in deviated and horizontal well drilling is hole cleaning, which involves the removal of drill cuttings and maintaining a clean borehole. Insufficient hole cleaning can lead to issues such as stuck pipe incidents, lost circulation, slow rate of penetration (ROP), difficult tripping operations, poor cementing, and formation damage. Insufficient advancements in real-time drilling evaluation for complex wells can also lead to drilling troubles and an increase in drilling costs. Therefore, this study aimed to develop a model for the hole-cleaning index (HCI) that could be integrated into drilling operations to provide an automated and real-time evaluation of deviated- and horizontal-drilling hole cleaning based on hydraulic and mechanical drilling parameters and drilling fluid rheological properties. This HCI model was validated and tested in the field in 3 wells, as it was applied when drilling 12.25″ intermediate directional sections and an 8.5″ liner directional section. The integration of the HCI in Well-A and Well-B helped achieve much better well drilling performance (50% ROP enhancement) and mitigate potential problems such as pipe sticking due to hole cleaning and the slower rate of penetration. Moreover, the HCI model was also able to identify hole-cleaning efficiency during a stuck pipe issue in Well-C, which highlights its potential usage as a real-time model for optimizing drilling performance and demonstrates its versatility.

H2S scavenging performance and rheological properties of water-based drilling fluids comprising ZIF-67

Exposure to the toxic hydrogen sulfide (H2S) gas during oilfield operations carries serious health and safety concerns, in addition to significant economic losses resulting from the corrosion and potential failures of the handling equipment. Although there are several H2S scavengers reported in the literature or commercially available, they have their own limitations in terms of efficacy, toxicity, and/or environmental impact, among others. Thus, we report herein, for the first time, the H2S scavenging performance of Zeolitic Imidazolate Framework-67 (ZIF-67) nanoparticles (NPs) and its effect on the rheological and fluid loss properties of water-based drilling mud. The synthesized ZIF-67 material was characterized using different characterization techniques. The incorporation of the ZIF-67 NPs into the drilling fluids was found to significantly enhance the H2S scavenging performance, where the breakthrough and saturation capacities in the presence of 1 wt.% ZIF-67 NPs were more than 2300 and 495%, respectively, higher than those obtained using the base drilling mud. The remarkable H2S scavenging performance of the ZIF-67 NPs in the drilling fluid can be attributed to their unique structural properties, abundant uncoordinated open metal (Co(II)) sites, high surface area, and the presence of active surface nitrogen functional groups. The fluid loss and rheological properties of the base drilling mud were not compromised by the addition of ZIF-67 NPs. Contrarily, the addition of ZIF-67 improved the plastic viscosity (PV), apparent viscosity (AV), yield point (YP), carrying capacity, and gel strength (GS) of the based mud. To the best of our knowledge, there are no published studies so far on H2S scavenging using any ZIF material while submerged in a liquid phase or incorporated into a drilling fluid, highlighting the novelty and significance of this work.

Semi-active structural vibration control with magnetorheological damper based on hybrid fuzzy sliding mode controller

Recently, structural vibration control has proved its capacity to save lives and keep structures safe during earthquakes. Furthermore, there is a wealth of research in both numerical and experimental studies. As a result, due to its simplicity and performance in mitigating structural vibrations generated by ground motions, semi-active control played a significant role in the majority of these studies. Nonetheless, the magnetorheological damper is the most often used semi-active device. In particular, the rheological fluid properties have gained adequate attention in earthquake energy dissipation and structural vibrations management, particularly in the civil engineering field. The semi-active control of three scaled excited structures is addressed in this study. A magnetorheological damper operated by a hybrid fuzzy sliding mode controller ensures the proposed control. However, to provide the appropriate current for the damper to operate, this proposed intelligent controller is combined with a clipped optimum algorithm. Otherwise, the numerical simulation results of the seismic excited scaled structure demonstrate the resilience of the suggested controller. As a result, four time-scaled seismic data are applied to the tested structure. Finally, the usefulness of the suggested semi-active control technique in mitigating earthquake structural vibration is demonstrated clearly in the compared controlled and uncontrolled responses.

Particle Image micro-Rheology (PIR) using displacement probability density function

We present a novel approach to perform passive microrheology. A method to measure the rheological properties of fluids from the Brownian motion of suspended particles. Rheological properties are found from the particles' mean square displacements (MSDs) as a function of measurement time lag. Current state-of-the-art approaches find the MSD by tracking multiple particles' trajectories. However, particle tracking approaches face many limitations, including low accuracy and high computational cost, and they are only applicable to low particle seeding densities. Here, we present a novel method, termed particle image rheometry (PIR), for estimating the particle ensemble MSD from the temporal evolution of the probability density function of the displacement as a function of measurement time lag. First, the probability density function (PDF) of the particle displacements for each time lag is found using a generalized ensemble image cross-correlation approach that eliminates the need for particle tracking. Then, PDFs are used to calculate the MSD from which the complex viscosity of the solution is measured. We evaluate the performance of PIR using synthetic datasets and show that it can achieve an error of less than 1% in passive microrheology measurements, which corresponds to a twofold lower error than existing methods. Finally, we compare the measured complex viscosity from PIR with bulk rheometry for a polymeric solution and show agreement between the two measurements.

A Methodical Approach to Scaling Up an Aerated Coaxial Mixer Containing a Shear-Thinning Fluid: Effect of the Fluid Rheology

The evolution of the rheological behavior of the fluid is one of the primary challenges encountered in the scale-up of the most aerated reactors. In fact, mixing efficiency diminishes because of the changes in the fluid rheological properties. Under these circumstances, it is challenging to keep the mass transfer constant upon scale-up. A thorough literature review revealed that no scale-up study of aerated coaxial mixers has considered the effect of varying fluid rheological properties. Therefore, to analyze the scale-up of these aerated mixing systems, the effects of the impeller speed and type, fluid rheology, and aeration rate on the gas hold-up, local mass transfer coefficient, bubble size distribution, hydrodynamics, and specific power consumption were explored. Electrical resistant tomography, dynamic gassing-in, and computational fluid dynamics methods were employed. For the first time, a systematic approach based on a constant volumetric mass transfer has been proposed for the scale-up of aerated coaxial reactors at different fluid rheological properties.