Article
Chemistry, Multidisciplinary
Sun Wanpeng, Zhu Chunying, Fu Taotao, Ma Youguang
Summary: This study numerically investigated the shape deformation of three bubbles rising in shear-thinning non-Newtonian fluids, revealing that bubble diameter, initial distance, and formation frequency significantly affect the aspect ratio of the bubbles.
IRANIAN JOURNAL OF CHEMISTRY & CHEMICAL ENGINEERING-INTERNATIONAL ENGLISH EDITION
(2021)
Article
Engineering, Marine
Zhen-Yu Hu, Shuai Li, Shi-Ping Wang, A-Man Zhang
Summary: In this study, the nonlinear bubble-plate interaction and the effect of fluid-structure interaction are investigated using boundary integral simulations and experiments. Different bubble collapse patterns and the impact of FSI on jet velocity and pressure are identified. Two scaling laws for plate motion with respect to geometry parameters are proposed.
Article
Mechanics
Andrea Aquino, Davide Picchi, Pietro Poesio
Summary: In this study, the dynamics of confined Taylor bubbles moving in an inelastic shear-thinning fluid were investigated through numerical simulations. The recent lubrication theory by Picchi et al. (2021) was validated and a general scaling that holds for both zero-shear-rate and shear-thinning effects was identified. Fluid rheology strongly influenced the shape of the Taylor bubble, competing with the capillary number. The viscosity fields analysis revealed an interplay between zero-shear rate and shear thinning effects in different regions of the bubble, including the formation of recirculating vortexes.
JOURNAL OF NON-NEWTONIAN FLUID MECHANICS
(2023)
Article
Engineering, Chemical
Kingsley Ezeji, Jaroslav Tihon
Summary: The study investigates the wall shear rate induced by large air bubbles rising in inclined rectangular channels using a two-strip electrodiffusion probe. Synchronized high-speed camera recordings provide additional information on bubble shapes and movements, while measurements are conducted over a wide range of operation parameters and inclination angles. The study aims to elucidate the influence of individual operating parameters on the bubble induced wall shear rate profile.
CHEMICAL ENGINEERING SCIENCE
(2022)
Article
Chemistry, Physical
Q. Chen, F. Restagno, D. Langevin, A. Salonen
Summary: Research shows that in micellar solutions, the rise velocity of bubbles decreases with increasing bubble volume fraction in low NaSal concentration Newtonian solutions, following the Richardson-Zaki prediction. However, in shear thinning viscoelastic solutions, bubble clustering leads to faster rise velocities and a weaker dependence on the bubble volume fraction. The peculiar dependence of rise velocity on bubble volume fraction in shear thinning viscoelastic solutions can have important implications in flotation.
JOURNAL OF COLLOID AND INTERFACE SCIENCE
(2022)
Article
Polymer Science
Vladimir Neverov, Vladimir Shelukhin
Summary: The processing of experimental data on particle settling in shear-thinning polymer solutions has led to the development of a mathematical model consisting of two continua. The model, which is consistent with basic thermodynamics laws, includes a correlation formula for gravitational mobility. The model has been validated through comparison with experimental and analytical data. The study also provides an explanation for the Boycott effect and demonstrates that sedimentation is enhanced in a 2D inclined vessel.
Article
Mechanics
Bo Yang, Mehdi Jafarian, Navid Freidoonimehr, Maziar Arjomandi
Summary: This study experimentally investigates the rising trajectory of a spherical microbubble with a diameter of 0.3-1.0mm in a vertical channel with fully developed laminar flow. The lift and drag forces on the bubble are assessed, and a new correlation for lift force coefficient is developed. The study concludes that the lift coefficient for a spherical microbubble in vertical channels with fully developed laminar flow is slightly higher than the reported shear lift coefficient for larger bubbles rising in a high viscous liquid.
INTERNATIONAL JOURNAL OF MULTIPHASE FLOW
(2022)
Article
Engineering, Chemical
Xin Dong, Xiaofei Xu, Zhijun Liu
Summary: Experimental and theoretical methods were used to investigate the behavior of bubble plume in crossflows. The influence of crossflow velocity, superficial gas velocity and rheology of liquid phase on the inclination trajectory of bubble plume was studied. The inclination angle of bubble plume in CMC aqueous solution was one-third more than that in tap water at high crossflow velocity.
CHEMICAL ENGINEERING RESEARCH & DESIGN
(2021)
Article
Thermodynamics
Shaobai Li, Jingbo Ji, Zhuang Liu
Summary: The motion of a single bubble rising in stagnant shear-thinning viscoelastic liquids was studied using a highspeed camera. Experimental observations of bubble volume, velocity, and drag coefficient were made and a shape map and empirical correlation were proposed.
EXPERIMENTAL THERMAL AND FLUID SCIENCE
(2022)
Article
Thermodynamics
Weihua Sun, Zhiyi Yu
Summary: This study investigates the bubble shape variation in a shear-thinning liquid and its effects on the flow. The results show that trailing bubbles accelerate and deform as they rise along the flow path. The shear-thinning property enhances the deformation and leads to an increase in the number of elongated bubbles. New correlations for the bubble aspect ratio are proposed and significantly improve the prediction accuracy for shear-thinning fluids compared to previous methods.
EXPERIMENTAL THERMAL AND FLUID SCIENCE
(2023)
Article
Engineering, Chemical
E. Revathi, V Deepak, S. Vengadesan
Summary: This study numerically investigates the dynamics of a Taylor drop rising in a vertical pipe with non-Newtonian behavior of the continuous phase. The effects of shear-thinning behavior, pipe diameter, and dispersed phase viscosity on the terminal velocity and drop shape are studied using the volume of fluid (VoF) based interFoam solver in OpenFOAM. The results show that the shear-thinning behavior of the continuous phase significantly influences both the terminal velocity and the shape of the drop. The Froude number correlation in the literature is extended for a Taylor drop rising in non-Newtonian liquid, with prediction errors within ±15%. The influence of a Taylor drop on wall shear stress for different CMC concentrations is also reported.
INDUSTRIAL & ENGINEERING CHEMISTRY RESEARCH
(2023)
Article
Engineering, Multidisciplinary
Michal Wrobel, Gennady Mishuris, Panos Papanastasiou
Summary: The study investigates the spatial and temporal evolution of fluid flow and resulting fracture geometry in a hydraulic fracture driven by a non-Newtonian shear-thinning fluid. The analysis demonstrates that rheological properties of fluids significantly impact the hydraulic fracturing process.
INTERNATIONAL JOURNAL OF ENGINEERING SCIENCE
(2021)
Review
Thermodynamics
Vadim S. Nikolayev
Summary: The Pulsating Heat Pipe (PHP) is a high performance passive heat transfer device that consists of folded capillary channels filled with liquid and vapor. Its advantage lies in heat exchange occurring through both latent heat transfer and liquid convection, but its non-stationary operation requires sophisticated direct modeling. A review of theoretical studies on PHP addresses physical phenomena at a single bubble and liquid plug level, discussing modeling and simulation of interactions between bubbles and plugs.
APPLIED THERMAL ENGINEERING
(2021)
Article
Nuclear Science & Technology
Zhongkai Mei, Xu Cheng
Summary: This study investigates the instantaneous hydrodynamics of a single bubble rising in quiescent water, including bubble trajectory, shape, and rising velocity. A new criterion, called bubble deformation factor, is calculated based on the three-dimensional normalized bubble interfacial area to analyze irregular shape oscillations. The study applies a moving reference frame to analyze the long-term dynamics of the bubble. The relationship between bubble shape and rising velocity is discussed, and the influence of surface tension on bubble hydrodynamics is illustrated. The accuracy of simulation results is validated through experimental data, and the feasibility of the method is verified by comparing it to theoretical correlations. The results show that the bubble deformation factor, representing shape oscillation, is feasible and sensitive to the bubble's motion pattern.
ANNALS OF NUCLEAR ENERGY
(2022)
Article
Engineering, Marine
Rui-Nan Cui, Shuai Li, Shi-Ping Wang, A-Man Zhang
Summary: In this study, the dynamics of high-pressure pulsating bubbles near a concave surface were investigated using experimental and numerical methods. Detailed information on bubble shapes, jet velocity, and wall pressure were obtained, and the validity of the numerical model was confirmed.
Article
Physics, Fluids & Plasmas
Vlasis Mitsoulas, Stylianos Varchanis, Yannis Dimakopoulos, John Tsamopoulos
Summary: The response of the endothelial glycocalyx (EG) to variations of the hemodynamic environment is crucial for maintaining blood vessel permeability and blood component balance. This study investigates the influence of geometric features and mechanical properties of individual fibers on the apparent permeability of EG, using modeling and experimental predictions.
PHYSICAL REVIEW FLUIDS
(2022)
Article
Mechanics
Marco De Corato, Daniele Tammaro, Pier Luca Maffettone, Norberto Fueyo
Summary: In this study, we investigate the retraction of a circular thin film coated with insoluble surfactants after being punctured. Our simulations show that the presence of surfactants slows down the retraction rate and introduces oscillations. As the surface elasticity increases, the film thickness perturbations spread over a larger area. Additionally, the surface perturbations travel faster than the retracting edge of the film at a speed proportional to the Gibbs modulus, approaching the behavior of an incompressible two-dimensional solid for large Gibbs modulus values.
JOURNAL OF FLUID MECHANICS
(2022)
Article
Physics, Fluids & Plasmas
D. Pettas, G. Karapetsas, Y. Dimakopoulos, J. Tsamopoulos
Summary: We investigated the flow of a Newtonian liquid film over an inclined hydrophobic wall textured with periodical microgrooves. Through numerical simulations and theoretical analysis, we explored the stability of the liquid flow under the influence of inertia, viscous, and capillary forces, as well as substrate wettability and geometric characteristics.
PHYSICAL REVIEW FLUIDS
(2022)
Article
Chemistry, Physical
Marco De Corato, Ignacio Pagonabarraga
Summary: This paper investigates the self-propulsion mechanism of chemically active colloids and their coupling relationship with chemical reactions and momentum transport. By studying Onsager reciprocal relations, it is found that if a chemical reaction drives the motion of the colloid, an external force generates a reaction rate. The validity of reciprocal relations is verified through numerical simulations, and the key role of solute advection in maintaining the symmetry of the Onsager matrix is highlighted. Furthermore, it is discovered that Onsager reciprocal relations break down under nonequilibrium steady states, which has implications for the thermal fluctuations of active colloids used in experiments.
JOURNAL OF CHEMICAL PHYSICS
(2022)
Article
Mechanics
Marco De Corato, Marino Arroyo
Summary: Chemically responsive polymers can respond to local variations in the chemical composition of a solution, leading to changes in their conformation and rheological properties. In this paper, a theory is developed to describe the flow of a mixture of solute and chemically responsive polymers, revealing novel couplings between the distribution of polymers and solutes.
JOURNAL OF RHEOLOGY
(2022)
Article
Mechanics
Konstantina Psaraki, Vlasios Mitsoulas, Stavros Pavlou, Yannis Dimakopoulos
Summary: We investigated the effects of variations in critical shearing parameters on the response of an endothelial cell monolayer. Specifically, we developed a rheometric emulation method that accounts for the interaction between blood plasma and deformable endothelial cells. Our findings provide quantitative predictions for the stresses on different cell compartments and their structural changes. In addition, we highlight the significance of the variation of Wall Shear Stress (WSS) along the cell membrane and its dependence on cell shape.
Article
Computer Science, Interdisciplinary Applications
Alexandros Syrakos, Oliver Oxtoby, Eugene de Villiers, Stylianos Varchanis, Yannis Dimakopoulos, John Tsamopoulos
Summary: This paper proposes a series of gradient reconstruction schemes based on orthogonal or oblique projections to solve over-determined systems. The schemes include weighted least-squares gradients and variations of consistent Green-Gauss gradients. Through testing and comparison on various grids, it is found that there may be numerical instability on high aspect ratio grids, and guidelines are provided for safely using weights within the least squares methods.
MATHEMATICS AND COMPUTERS IN SIMULATION
(2023)
Article
Mechanics
G. Esposito, Y. Dimakopoulos, J. Tsamopoulos
Summary: This study investigates the motion of a viscous drop rising in a viscoelastic liquid with elastic and shear thinning effects. The numerical predictions are validated by comparing them with experimental data, showing agreement in terminal velocities and drop shapes. The interplay of viscous, elastic, and capillary forces is explored through a parametric study. Key findings include the transformation of a spherical drop into one with a cusp and an extended tail due to increasing material elasticity, and the confirmation that viscoelastic materials can encapsulate liquid drops generated by liquid filaments.
JOURNAL OF NON-NEWTONIAN FLUID MECHANICS
(2023)
Article
Chemistry, Multidisciplinary
Eleni Kouni, Pantelis Moschopoulos, Yannis Dimakopoulos, John Tsamopoulos
Summary: When a charged particle moves through a solution, the surrounding electric double layer deforms in response to fluid motion, creating an electric force opposite to the particle's direction of motion, which reduces its settling velocity. This phenomenon combines fluid mechanics and electrodynamics, and differs from the classical problem of an uncharged sedimenting particle. Its applications range from mechanical to biomedical fields.
Article
Physics, Multidisciplinary
Gaspard Junot, Marco De Corato, Pietro Tierno
Summary: We observe the emergence of large zigzag bands in a population of actuated magnetic rotors, which behave as active shakers. By combining experimental analysis with simulations, we show that the special flow field created by the shakers is the key ingredient for the observed spatiotemporal pattern.
PHYSICAL REVIEW LETTERS
(2023)
Article
Physics, Fluids & Plasmas
A. Kordalis, D. Pema, S. Androulakis, Y. Dimakopoulos, J. Tsamopoulos
Summary: This study investigates the buoyancy-driven rise and interaction between two coaxial bubbles in an elastoviscoplastic material. The development of a shear stress bridge between the bubbles decreases drag force on the trailing bubble, initiating their approach. The material's solidlike behavior makes it softer for the trailing bubble. Normal stresses primarily extend the bubbles, but the leading bubble eventually adopts a less favorable shape that slows it down. Geometric characteristics and material properties also affect the approach time.
PHYSICAL REVIEW FLUIDS
(2023)
Article
Chemistry, Physical
P. Moschopoulos, E. Kouni, K. Psaraki, Y. Dimakopoulos, J. Tsamopoulos
Summary: This study investigates the stretching dynamics of a yield stress material with both elastic and viscoplastic behavior. The material forms a cylindrical liquid bridge initially and then a neck when subjected to stretching between coaxial disks. Theoretical analysis shows that an elongated thin neck is formed due to elasticity, connecting the upper and lower parts of the bridge. The findings suggest that the consideration of elasticity affects the pinching times and filament length in filament stretching procedures of yield stress materials.