Korea-Australia Rheology Journal最新文献

The settling stability of magnetorheological fluid (MRF) is an important aspect of magnetorheological research and an important indicator of MRF quality. The discrete element method (DEM) was proposed to study the multi-particle settling process of particles dispersed in silicon oil with different iron powder content, particle size, base viscosity, and added magnetic field. Then by preparing MRF, the zero-field viscosity, dynamic magnetic field viscosity, and settling stability of various MRF were measured and analyzed. The results show that the average kinetic energy of MRF settling decreases as particle content, particle size, and base fluid viscosity increase. With 50% iron powder content, 300 nm particle size, and 5% bentonite additive, MRF has the highest viscosity under zero field; under a dynamic magnetic field, the larger the particle size, the larger the viscosity; the MRF settling rate decreases by 18% with a change in iron powder content, decreases by 22.5% with a change in particle size to 300 nm, and decreases by 22% with a change in bentonite content. Under the application of a magnetic field, MRF hardly settles. The final experimental and simulation results are comparable, indicating that the MRF settlement characteristics can be predicted to some extent with the help of DEM simulation.

The main objective of food rheology is to identify food structure and texture by rheological measurements, thereby reducing the requirement for sensory analysis in evaluating food products. However, determining food texture and structure exclusively from rheological measurements can be challenging because of the complicated composition and structure of food, as well as the complexities of factoring in the changes that occur during food mastication. This article provides a comprehensive review of the current experimental, computational and machine learning techniques used in food rheology to probe the structure and texture of food products. The textural attributes and structural information that can be inferred from each measurement technique is discussed and recent studies that carried out the measurements are highlighted. Also presented in this review are the recent progress in the experimental techniques and challenges.

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Bacterial biofilms, as viscoelastic materials, have significant implications in various fields of human life encompassing health, manufacturing, and wastewater treatment. The detailed rheological characterization of mechanical properties, viscoelastic characteristics, and shear behaviors of biofilms is crucial for both scientific insight and practical applications. This review provides an exhaustive examination of bacterial biofilm formation and growth through rheological techniques, representing a critical intersection between microbiology and materials science. It explores different rheological methods, geometries, and devices, offering a comprehensive understanding of how rheological measurements can be applied to study biofilms. The advantages, limitations, and challenges of rheological techniques are also analyzed, emphasizing the importance of choosing appropriate methods for specific applications.

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Particulate flows occur in various natural and technological settings. Understanding what influences the flow characteristics and how they can be manipulated is significant from scientific and engineering perspectives. In this paper, we review the lattice Boltzmann method combined with the smoothed profile method (LBM–SPM), one of the promising simulation methods for studying particle-containing systems. We present the background theory and numerical schemes of the LBM–SPM, then review several applications of this method for particulate flows; suspension rheology, deposition and clogging of particles within the flow, and the dynamics of particles in non-Newtonian media and at the fluid interface. Finally, we confirmed the versatility and feasibility of LBM–SPM for investigating particulate flows.

Computer simulation and modeling have proven to be powerful tools in the fields of engineering and polymer science. These computational methods not only enable us to verify experimentally observed behaviors, but also provide answers to unsolved phenomena. This review addresses the current status and trends of computational and theoretical studies in polymer blends. We briefly discuss the fundamental aspects of polymer blends, including experimental observations, theories, and a variety of molecular simulations and models for mixtures of two or more polymeric materials. In particular, this study deals with the description of coarse-grained techniques that can offer perspectives into the collective behavior and properties of complicated systems. Additionally, a detailed analysis of their structural, rheological, and mechanical properties via computation is also examined. Lastly, we summarize important findings and highlight points to be carefully considered in modeling polymer blends system accompanied by an outlook on the extension of current studies to complicated systems of many blending types.

The double-lumen cannula (DLC) is the most critical component of extracorporeal membrane oxygenation (ECMO) because of its narrow cross-section, thereby developing the highest shear stress in the entire ECMO circuit. To measure blood damage in a DLC, the Eulerian approach is generally used without contemplating exposure time or history of blood exposure to shear stresses. Alternatively, Lagrangian approach has also been recently employed for a Newtonian blood flow through a DLC, thereby leaving a research gap on the impact of variable shear rate in case of non-Newtonian blood flow. In the present study, the hemodynamic performance of DLC is investigated using different non-Newtonian models by applying Lagrangian approach. Moreover, the motion of RBC was tracked inside the cannula to predict its behavior during the motion. The results showed that the return lumen had higher pressure, velocity, and shear stress values than other parts of the DLC. In addition, recirculation was observed due to the mixing of blood coming from different inlets and found increase with increasing flow rate of blood. Moreover, it was found that the blood damage increased with increasing flow rate. There was more blood damage in the Newtonian model than in the other non-Newtonian models at higher flow rates. However, the Carreau model showed more blood damage at lower flow rates than the other models. The Cross model showed DLC’s higher efficacy in delivering oxygenated blood to the tricuspid outlet because it showed the least blood damage among all other models. It was also concluded that the efficacy of the DLC to deliver oxygenated blood to the tricuspid outlet decreases with increasing blood flow rate.

The rheological and electrical properties of polyvinyl alcohol (PVA)/silver nanowire (AgNW) suspensions and films are investigated with increasing AgNW concentrations, employing AgNWs with two different aspect ratios, namely 714 and 1000 (referred to as Ag714 and Ag1000, respectively). To estimate the effect of the aspect ratio on the rheological and electrical percolation behavior, the linear rheological properties of suspensions and the electrical properties of the resulting films are systematically assessed. The microstructure of the suspensions and the surface morphology of the films are visualized using optical microscope (OM) and field emission scanning electron microscope (FE-SEM), respectively. Observations from OM analyses reveal that suspensions containing higher aspect ratio AgNW (Ag1000) exhibit larger flocculated clusters, resulting from the entanglement of the nanowires. As results, PVA/Ag1000 suspensions show higher linear viscoelasticity (as indicated by G′ and G″) when compared to PVA/Ag714 suspensions. However, unlike linear viscoelasticity, the electrical conductivities of PVA/Ag1000 films are lower than those of PVA/Ag714 films. This observation is attributed to the alignment of AgNWs during coating process providing substantial deformation and rapid alignment. Furthermore, SEM images of the films confirm the importance of retaining the flocculated clusters to achieve the desired electrical properties.

In this study, we investigated the electrorheological characteristics of a fibrous hydrated magnesium silicate, sepiolite suspension. The sepiolite nanoparticles were heat-treated between 150 and 900 °C, and 2 wt% sepiolite was dispersed in silicone oil. The structural change of the baked particles was analyzed. The effects of the particle loading and applied voltage were evaluated. It was found that the heat-treated sepiolite suspension showed relatively higher viscosity, storage modulus and loss modulus. In addition, as the applied voltage increased, the shear yield stress increased. When a 9 kV/mm direct current (DC) field was applied, a shear yield stress of 16.8 kPa was measured.

Yam is a vegetable that is widely grown around the world. Yam mucilage contains a high mucin concentration that can be useful for supporting the swallowing process. Although the shear and extensional rheology of yam mucilage is essential to its flow, they have not received much attention. Using a commercial rheometer and a filament stretching rheometer, the rheological properties of the mucilage in yam were examined. Yam mucilage exhibits shear-thinning behavior and viscoelastic behavior. In addition, yam mucilage also exhibits stretching phenomena and shows high extensional viscosity. However, the elasticity of yam mucilage decreased when the shear increased. The extensional rheological behavior of the yam mucilage can be predicted by two models, including the Giesekus model and global function. However, the agreement between the model and the experimental data decreases gradually when the Hencky strain increases, even though the model can predict the shear viscosity data well.

This paper presents a comprehensive review of the partitioned pipe mixer (PPM) and its design variants: the barrier-embedded partitioned pipe mixer (BPPM) and the groove-embedded partitioned pipe mixer (GPPM). These mixers utilize chaotic advection as their mixing mechanism in the laminar flow regime. The review first focuses on the flow and mixing characteristics of these mixers, considering the influence of the operating conditions and design variables. The advantages and flexibility of the BPPM and GPPM over the original PPM are highlighted. The investigation covers mixing performance in both the creeping and non-creeping flow regimes. In addition, this review examines the impact of thixotropy and fluid inertia on mixing performance of the mixers, revealing irregular trends. It emphasizes the importance of carefully considering thixotropy and inertia when selecting appropriate mixing protocols and operating conditions. Furthermore, the potential use of chaotic mixing by the BPPM in filtration processes is briefly reviewed. In conclusion, the review summarizes the limitations of the previous studies and suggesting future research directions. Further studies are expected to explore the potential of these types of mixers in improving mixing performance in various industries, particularly those dealing with rheologically complex fluids.

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