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shear-thinning
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Investigation of bubble formation and its detachment in shear-thinning liquids at low capillary and Bond numbers
, Article Theoretical and Computational Fluid Dynamics ; Volume 33, Issue 5 , 2019 , Pages 463-480 ; 09354964 (ISSN) ; Afshin, H ; Firoozabadi, B ; Sharif University of Technology
Springer New York LLC
2019
Abstract
In the present paper, the formation of an air bubble in a shear-thinning non-Newtonian fluid was investigated numerically. For modeling, an algebraic volume of fluid (VOF) solver of OpenFOAM ® was improved by applying a Laplacian filter and was evaluated using the experimental results from the literature. The enhanced solver could compute the surface tension force more accurately, and it was important especially at low capillary and Bond numbers due to the dominance of surface tension force relative to the other forces. The adiabatic bubble growth was simulated in an axisymmetric domain for Bo = 0.05 , 0.1 , 0.5 and Ca = 10 - 1, 10 - 2, 10 - 3, 10 - 4, and the bubble detachment time and...
Enhanced oil-in-water droplet generation in a T-junction microchannel using water-based nanofluids with shear-thinning behavior: A numerical study
, Article Physics of Fluids ; Volume 33, Issue 1 , 2021 ; 10706631 (ISSN) ; Shamloo, A ; Kazemzadeh Hannani, S ; Sharif University of Technology
American Institute of Physics Inc
2021
Abstract
Nanofluids are widely used as the continuous phase during droplet formation in microsystems due to their impressive features such as excellent thermal, magnetic, and interfacial properties. Although it is well-known that nanofluids are susceptible to exhibit non-Newtonian behavior even at a low concentration of nanoparticles, effects of non-Newtonian behavior of nanofluids have not been studied on droplet formation thus far. In this study, oil-in-water droplet formation with a relatively high viscosity ratio of the immiscible phases was studied numerically in a T-junction microchannel. To inspect the non-Newtonian effects of aqueous nanofluids on droplet formation, empirical data on the...
Experimental investigation and comparison of Newtonian and non-Newtonian shear-thinning drop formation
, Article Experimental Thermal and Fluid Science ; Volume 94 , 2018 , Pages 148-158 ; 08941777 (ISSN) ; Esfidani, M. T ; Afshin, H ; Firoozabadi, B ; Sharif University of Technology
Elsevier Inc
2018
Abstract
The presence of small amount of polymer in Newtonian liquids affects the fluid behavior significantly and creates superficial differences between Newtonian and non-Newtonian drop formation. In the present study, Newtonian and non-Newtonian shear-thinning drop formation in air is examined experimentally and the geometrical parameters, such as drop elongation length, minimum neck diameter and current contact angle are studied for water, glycerin solutions (79, 89 and 94% w/w) and Carboxymethyl cellulose (CMC) solutions (0.5 to 1.5% w/w) drops. The results indicate that at initial stages of the drop growth, Newtonian and non-Newtonian liquids behave similarly. However, at the start of the...
Experimental investigation of the bubble motion and its ascension in a quiescent viscous liquid
, Article Experimental Thermal and Fluid Science ; Volume 103 , 2019 , Pages 274-285 ; 08941777 (ISSN) ; Shahsavari, M ; Afshin, H ; Firoozabadi, B ; Sharif University of Technology
Elsevier Inc
2019
Abstract
In the present research, the rising behavior of air bubble in a viscous liquid is investigated experimentally. Aqueous solutions of glycerol and CMC were used as the Newtonian and shear-thinning non-Newtonian viscous liquids, respectively. The bubble is formed via injection of air by a syringe pump and rises in the quiescent viscous liquid. The process was captured using a high-speed camera (1000 fps) and was post processed to obtain the bubble characteristics such as the center of mass and aspect ratio. The experimental results were verified using the existing literatures and the non-dimensional numbers were reduced to two (Velocity number and Flow number) by lumping the parameters. In...
Effect of temperature and concentration on thermal conductivity and viscosity of ferrofluid loaded with carbon nanotubes
, Article Heat and Mass Transfer/Waerme- und Stoffuebertragung ; 2015 , Pages 1-9 ; 09477411 (ISSN) ; Saghafian, M ; Salimpour, M. R ; Shafii, M. B ; Sharif University of Technology
Springer Verlag
2015
Abstract
The aim of this paper is to investigate the thermal conductivity and viscosity of a hybrid nanofluid containing tetramethylammonium hydroxide (TMAH) coated Fe3O4 nanoparticles and gum arabic (GA) coated carbon nanotubes (CNTs), experimentally. The magnetic nanoparticles and CNTs are physically attached as the result of interaction between the TMAH and GA molecules. The morphology and structure of the samples are characterized with X-ray diffraction (XRD) and transmission electron microscopy (TEM). The experiments are carried out in the magnetic nanoparticles volume concentration range of 0.1–0.9 %, CNT volume concentration range of 0.05–1.35 % and the temperature range of 25–55 °C. The...
Effect of magnetic field on thermal conductivity and viscosity of a magnetic nanofluid loaded with carbon nanotubes
, Article Journal of Mechanical Science and Technology ; Volume 30, Issue 2 , 2016 , Pages 809-815 ; 1738494X (ISSN) ; Salim Pour, M. R ; Saghafian, M ; Shafii, M. B ; Sharif University of Technology
Korean Society of Mechanical Engineers
Abstract
The present work examines experimentally the effect of magnetic field on the viscosity and thermal conductivity of a hybrid nanofluid containing tetramethylammonium hydroxide (TMAH) coated Fe3O4 nanoparticles and Gum arabic (GA) coated carbon nanotubes (CNTs). The hybrid nanofluid was prepared by using ultrasonic dispersion method. Magnetic field was created by a pair of spaced apart magnet plates. The effect of temperature on the time variation of thermal conductivity under applied magnetic field was also investigated. According to the results of this study, viscosity of the hybrid nanofluid increases with the strength of magnetic field, while it decreases with the increase of temperature....
Effect of temperature and concentration on thermal conductivity and viscosity of ferrofluid loaded with carbon nanotubes
, Article Heat and Mass Transfer/Waerme- und Stoffuebertragung ; Volume 52, Issue 10 , 2016 , Pages 2293-2301 ; 09477411 (ISSN) ; Saghafian, M ; Salimpour, M. R ; Shafii, M. B ; Sharif University of Technology
Springer Verlag
2016
Abstract
The aim of this paper is to investigate the thermal conductivity and viscosity of a hybrid nanofluid containing tetramethylammonium hydroxide (TMAH) coated Fe3O4 nanoparticles and gum arabic (GA) coated carbon nanotubes (CNTs), experimentally. The magnetic nanoparticles and CNTs are physically attached as the result of interaction between the TMAH and GA molecules. The morphology and structure of the samples are characterized with X-ray diffraction (XRD) and transmission electron microscopy (TEM). The experiments are carried out in the magnetic nanoparticles volume concentration range of 0.1–0.9 %, CNT volume concentration range of 0.05–1.35 % and the temperature range of 25–55 °C. The...
Modeling and experimental investigation of bubble formation in shear-thinning liquids
, Article Journal of Fluids Engineering, Transactions of the ASME ; Volume 139, Issue 7 , 2017 ; 00982202 (ISSN) ; Reza Oshaghi, M ; Afshin, H ; Firoozabadi, B ; Sharif University of Technology
American Society of Mechanical Engineers (ASME)
2017
Abstract
This investigation presents both theoretical and experimental studies on the size of a growing bubble in power-law non-Newtonian liquids. At first, some previous works on the prediction of bubble size in Newtonian liquids have been extended by considering the balance of forces acting on the bubble at the moment of separation. Predicted bubble sizes were validated against the experimental results for a wide range of operating conditions, including different gas flow rates and needle diameters as well as a wide range of physical properties of the Newtonian liquids. Furthermore, in order to determine the size of the bubbles formed in power-law non-Newtonian liquids with a similar analysis, the...
Pressure drop reduction of power-law fluids in hydrophobic microgrooved channels
, Article Physics of Fluids ; Volume 31, Issue 7 , 2019 ; 10706631 (ISSN) ; Moosavi, A ; Sharif University of Technology
American Institute of Physics Inc
2019
Abstract
Using hydrophobic surfaces is one of the efficient methods to preserve energy in fluid transfer systems. However, the studies have been concentrated on Newtonian fluids despite the wide applications of non-Newtonian fluids in daily life and many industries such as the biological, foodstuff, chemical, petroleum, cosmetic, and lab on a chip fields. In this study, we consider power-law fluids as a typical example of non-Newtonian fluids and investigate the effect of hydrophobic microgrooves on the pressure drop in channels by utilizing the phase field method. We demonstrate that the optimum size of the rectangular microgrooves in which the maximum pressure drop reduction (PDR) happens for both...
Electrowetting of power-law fluids in microgrooved channels
, Article Physics of Fluids ; Volume 32, Issue 7 , July , 2020 ; Moosavi, A ; Sharif University of Technology
American Institute of Physics Inc
2020
Abstract
Studying the dynamic behavior of droplets is of great importance in the electrowetting phenomena. However, despite the widespread use of non-Newtonian fluids in industry and daily life including medicine, food, petroleum, environmental biomass, and lab on a chip, most studies have focused on Newtonian fluids. In this study, a power-law fluid is considered as a typical example of non-Newtonian fluids and its dynamic behavior is investigated within a microchannel, and the results are compared with those of the Newtonian fluids. Both the grooved and non-grooved substrates are considered. For this purpose, the governing equations for the two phase fluid flow are solved using the finite element...
Computational simulation of non-Newtonian blood flow in carotid bifurcation for investigation the various rheological blood models
, Article ASME 2007 International Mechanical Engineering Congress and Exposition, IMECE 2007, 11 November 2007 through 15 November 2007 ; Volume 2 , 2007 , Pages 263-270 ; 0791842967 (ISBN) ; Firoozabadi, B ; Goodarzvand Chegini, A ; ASME ; Sharif University of Technology
American Society of Mechanical Engineers (ASME)
2007
Abstract
One of the leading causes for death after heart diseases and cancer in all over the world is still stroke. Most strokes happen because an artery carrying blood from the heart to the brain is clogged. Most of the time, as with heart attacks, the problem is atherosclerosis, hardening of the arteries, calcified build up of fatty deposits on the vessel wall. The primary troublemaker is the carotid artery, one on each side of the neck, the main thoroughfare for blood to the brain. In this study, the fluid dynamic simulations were done in the carotid bifurcation artery for studying the formation of atherosclerosis, and shear thinning behavior of blood as well as Newtonian comportment was studied....
Shear-thinning droplet formation inside a microfluidic T-junction under an electric field
, Article Acta Mechanica ; Volume 232, Issue 7 , 2021 , Pages 2535-2554 ; 00015970 (ISSN) ; Honarmand, M ; Dizani, M ; Moosavi, A ; Kazemzadeh Hannani, S ; Sharif University of Technology
Springer
2021
Abstract
Researchers usually simplify their simulations by considering the Newtonian fluid assumption in microfluidic devices. However, it is essential to study the behavior of real non-Newtonian fluids in such systems. Moreover, using the external electric or magnetic fields in these systems can be very beneficial for manipulating the droplet size. This study considers the simulation of the process of non-Newtonian droplets’ formation under the influence of an external electric field. The novelty of this study is the use of a shear-thinning fluid as the droplet phase in this process, which has been less studied despite its numerous applications. The effects of an external electric field on this...
Herschel-Bulkley rheological parameters of lightweight colloidal gas aphron (CGA) based fluids
, Article Chemical Engineering Research and Design ; Volume 93 , 2015 , Pages 21-29 ; 02638762 (ISSN) ; Arabloo, M ; Ghazanfari, M. H ; Rashtchian, D ; Sharif University of Technology
Institution of Chemical Engineers
2015
Abstract
The proper understanding of rheological characteristics of CGA based fluids is of crucial importance in determining the performance of the fluid, in order to maintain the most effective fluid properties for safe, efficient, and economical drilling operation. This paper presents a concise investigation on the effect of concentration of the three main components of a novel environmentally friendly lightweight CGA based drilling fluid, i.e., xanthan gum biopolymer, starch, and biosurfactant, to the Herschel-Bulkley rheological model parameters. The three parameters of Herschel-Bulkley model, i.e., yield stress, fluid consistency, and fluid flow index were calculated by fitting the experimental...
Modelling of power-law fluid flow through porous media using smoothed particle hydrodynamics
, Article Transport in Porous Media ; Volume 74, Issue 3 , 2008 , Pages 331-346 ; 01693913 (ISSN) ; Manzari, M. T ; Sharif University of Technology
2008
Abstract
The flow of non-Newtonian fluids through two-dimensional porous media is analyzed at the pore scale using the smoothed particle hydrodynamics (SPH) method. A fully explicit projection method is used to simulate incompressible flow. This study focuses on a shear-thinning power-law model (n < 1), though the method is sufficiently general to include other stress-shear rate relationships. The capabilities of the proposed method are demonstrated by analyzing a Poiseuille problem at low Reynolds numbers. Two test cases are also solved to evaluate validity of Darcy's law for power-law fluids and to investigate the effect of anisotropy at the pore scale. Results show that the proposed algorithm can...
On the motion of Newtonian and non-Newtonian liquid drops
, Article Scientia Iranica ; Volume 19, Issue 5 , 2012 , Pages 1265-1278 ; 10263098 (ISSN) ; Maleki, A ; Firoozabadi, B ; Afshin, H ; Sharif University of Technology
2012
Abstract
In the present study, the motion of Newtonian and non-Newtonian liquid drops has been investigated experimentally. In order to investigate the effect of bulk fluid on drops, we have used water and air, as two fluids with different properties, and various industrial and biological applications. Image processing is utilized to analyze the images obtained by a high speed camera. The research has been separated into two parts. The first part has been devoted to the experiments in which air is the bulk fluid, and the second is related to the experiment carried out in water. The range of Reynolds number is, approximately, 50
Electroosmotic flow of power-law fluids with temperature dependent properties
, Article Journal of Non-Newtonian Fluid Mechanics ; Volume 185-186 , 2012 , Pages 49-57 ; 03770257 (ISSN) ; Saidi, M. H ; Sadeghi, A ; Sharif University of Technology
Elsevier
2012
Abstract
The influence of variable fluid properties on mixed electroosmotic and pressure driven flow of non-Newtonian fluids is investigated in this paper. The non-linear coupled energy and momentum equations are solved by means of an iterative numerical approach. The results reveal that the temperature dependent effects only become significant at very high values of the Debye-Hückel parameter in case of combined electroosmotic and pressure driven flow and could safely be neglected in other cases. It is observed that the physical properties variation lead to a higher mean velocity in case of pressure assisted flow and a lower mean velocity in case of pressure opposed flow. Furthermore, the...
Rheology, stability and filtration characteristics of colloidal gas aphron fluids: role of surfactant and polymer type
, Article Journal of Natural Gas Science and Engineering ; Volume 26 , September , 2015 , Pages 895-906 ; 18755100 (ISSN) ; Arabloo, M ; Ghazanfari, M. H ; Sharif University of Technology
Elsevier
2015
Abstract
Colloidal Gas Aphron (CGA) are finding increasing application in fields of science and engineering because of their distinctive characteristic. As interest in the application of CGA based fluids grows and in order to select the best procedure for using them in successful petroleum engineering operations, there is a need to gain a better understanding of the factors that affect their properties and behavior. This article discusses the rheological characterization, stability analysis and filtration properties of CGA based fluids for three bio-polymers and two ionic surfactant. The stability and filtration analysis were investigated with the static drain rate technique and API filtration tests,...
Shear-rate-dependent rheology effects on mass transport and surface reactions in biomicrofluidic devices
, Article AIChE Journal ; Volume 61, Issue 6 , 2015 , Pages 1912-1924 ; 00011541 (ISSN) ; Amini, Y ; Saidi, M. H ; Yavari, H ; Sharif University of Technology
John Wiley and Sons Inc
2015
Abstract
Consideration is given to shear-rate-dependent rheology effects on mass transport in a heterogeneous microreactor of rectangular cross section, utilizing both numerical and analytical approaches. The carrier liquid obeys the power-law viscosity model and is actuated primarily by an electrokinetic pumping mechanism. It is discovered that, considering the shear-thinning biofluids to be Newtonian fluids gives rise to an overestimation of the saturation time. The degree of overestimation is higher in the presence of large Damkohler numbers and electric double layer thicknesses. It is also increased by the application of a favorable pressure gradient, whereas the opposite is true when an opposed...
Synthesis and analysis of the properties of ferro-fluids
, Article ICONN 2010 - Proceedings of the 2010 International Conference on Nanoscience and Nanotechnology, 22 February 2010 through 26 February 2010, Sydney, NSW ; 2010 , Pages 91-93 ; 9781424452620 (ISBN) ; Ghane Motlagh, B ; Ghane Golmohamadi, F ; Ghane Motlagh, R ; Rouhani, S ; Sharif University of Technology
2010
Abstract
We report the rheological properties of ferro-fluid (FF) containing iron oxide nano-particles. At first, a FF was synthesized by using chemical co-precipitaton[1]. The microstructure study using SEM revealed that the FF contained nano-particles with the mean particle size of 35nm. The XRD study revealed that we have well crystallized structures of magnetite; they appeared to be approximately single crystalline structures. The rheological results proved that the FF has non Newtonian behavior, it is a shear thinning fluid in all magnetic fields, Moreover, the magnetic field increases the viscosity in a definite shear rate due to the nano-particles agglomerations and formation of chain-like...
Mass transport analysis of non-Newtonian fluids under combined electroosmotically and pressure driven flow in rectangular microreactors
, Article Colloids and Surfaces A: Physicochemical and Engineering Aspects ; Volume 508 , 2016 , Pages 345-359 ; 09277757 (ISSN) ; Saidi, M. H ; Sharif University of Technology
Elsevier
Abstract
Hydrodynamically fully developed flow of power-law fluids under combined action of electroosmotic and pressure gradient forces in rectangular microreactors is analyzed considering heterogeneous catalytic reactions. The Poisson-Boltzmann, Cauchy momentum, and concentration equations are considered in two dimensions and after being dimensionless are numerically solved applying a finite difference algorithm. Variation of axial concentration gradient, and axial and horizontal mass diffusions are taken into account as well. To accomplish a more general analysis, the velocity distribution is obtained by solving continuity and Cauchy momentum equations and is not considered as an average axial...