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    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) Taghi Esfidani, M ; 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) Javaherchian, J ; 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 Izadi, R ; 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... 

    An investigation on the body force modeling in a lattice Boltzmann BGK simulation of generalized Newtonian fluids

    , Article Physica A: Statistical Mechanics and its Applications ; Vol. 415, issue , 2014 , pp. 315-332 Farnoush, S ; Manzari, M. T ; Sharif University of Technology
    Abstract
    Body force modeling is studied in the Generalized Newtonian (GN) fluid flow simulation using a single relaxation time lattice Boltzmann (LB) method. First, in a shear thickening Poiseuille flow, the necessity for studying body force modeling in the LB method is explained. Then, a parametric unified framework is constructed for the first time which is composed of a parametric LB model and its associated macroscopic dual equations in both steady state and transient simulations. This unified framework is used to compare the macroscopic behavior of different forcing models. Besides, using this unified framework, a new forcing model for steady state simulations is devised. Finally, by solving a... 

    Electrokinetic mixing and displacement of charged droplets in hydrogels

    , Article Transport in Porous Media ; Vol. 104, Issue. 3 , Jun , 2014 , pp. 469-499 ; ISSN: 01693913 Mohammadi, A ; Sharif University of Technology
    Abstract
    Mixing in droplets is an essential task in a variety of microfluidic systems. Inspired by electrokinetic mixing, electric field-induced hydrodynamic flow inside a charged droplet embedded in an unbounded polyelectrolyte hydrogel is investigated theoretically. In this study, the polyelectrolyte hydrogel is modeled as a soft, and electrically charged porous solid saturated with a salted Newtonian fluid, and the droplet is considered an incompressible Newtonian fluid. The droplet-hydrogel interface is modeled as a surface, which is located at the plane of shear, with the electrostatic potential ζ. The fluid inside the droplet attains a finite velocity owing to hydrodynamic coupling with the... 

    Pressure effects on electroosmotic flow of power-law fluids in rectangular microchannels

    , Article Theoretical and Computational Fluid Dynamics ; Vol. 28, issue. 4 , 2014 , pp. 409-426 ; ISSN: 09354964 Vakili, M. A ; Sadeghi, A ; Saidi, M. H ; Sharif University of Technology
    Abstract
    In this paper, the fully developed electroosmotic flow of power-law fluids in rectangular microchannels in the presence of pressure gradient is analyzed. The electrical potential and momentum equations are numerically solved through a finite difference procedure for a non-uniform grid. A complete parametric study reveals that the pressure effects are more pronounced at higher values of the channel aspect ratio and smaller values of the flow behavior index. The Poiseuille number is found to be an increasing function of the channel aspect ratio for pressure assisted flow and a decreasing function of this parameter for pressure opposed flow. It is also observed that the Poiseuille number is... 

    Electrophoretic velocity of spherical particles in Quemada fluids

    , Article Colloids and Surfaces A: Physicochemical and Engineering Aspects ; Volume 436 , September , 2013 , Pages 225-230 ; 09277757 (ISSN) Moosavi, S. M ; Sadeghi, A ; Saidi, M. S ; Sharif University of Technology
    2013
    Abstract
    The biomicrofluidic devices utilizing electrophoresis for sample manipulation are usually encountered with non-Newtonian behavior of working fluids. Hence, developing theoretical models capable of predicting the electrophoretic velocity of colloidal particles in non-Newtonian fluids is of high importance for accurate design and active control of these devices. The present investigation is dealing with the electrophoresis of a spherical particle in a biofluid obeying the Quemada rheological model. The sphere radius is considered to be significantly larger than the Debye length. Moreover, it is assumed that the particle zeta potential is small so that the Debye-Hückel linearization is... 

    Electric-field-induced response of a droplet embedded in a polyelectrolyte gel

    , Article Physics of Fluids ; Volume 25, Issue 8 , 2013 ; 10706631 (ISSN) Mohammadi, A ; Sharif University of Technology
    2013
    Abstract
    The electric-field induced response of a droplet embedded in a quenched polyelectrolyte gel is calculated theoretically. The response comprises the droplet translation and the electric-field induced flow fields within the droplet. The gel is modeled as a soft, and electrically charged porous solid saturated with a salted Newtonian fluid. The droplet is considered an incompressible Newtonian fluid with no free charge. An analytical solution, using the perturbation methodology and linear superposition, is obtained for the leading-order steady response to a DC electric-field. The fluid within the droplet is driven due to hydrodynamic coupling with the electroosmotic flow. The fluid velocity... 

    Joule heating effects in electrokinetically driven flow through rectangular microchannels: An analytical approach

    , Article Nanoscale and Microscale Thermophysical Engineering ; Volume 17, Issue 3 , 2013 , Pages 173-193 ; 15567265 (ISSN) Sadeghi, A ; Kazemi, Y ; Saidi, M. H ; Sharif University of Technology
    2013
    Abstract
    This is a theoretical study dealing with mixed electroosmotic and pressure-driven flow of a Newtonian liquid in a rectangular microchannel. Both and thermal boundary conditions are considered and the Debye-Hückel linearization is invoked. The governing equations are made dimensionless assuming fully developed conditions and then analytically solved using an infinite series solution. The governing factors are found to be the dimensionless Debye-Hückel parameter, velocity scale ratio, dimensionless Joule heating parameter, and channel aspect ratio. The results indicate that the Nusselt number is an increasing function of the channel aspect ratio, whereas the opposite is true for the velocity... 

    Experimental investigation of rheological and morphological properties of water in crude oil emulsions stabilized by a lipophilic surfactant

    , Article Journal of Dispersion Science and Technology ; Volume 34, Issue 3 , Feb , 2013 , Pages 356-368 ; 01932691 (ISSN) Sadeghi, M. B ; Ramazani, S. A. A ; Taghikhani, V ; Ghotbi, C ; Sharif University of Technology
    2013
    Abstract
    Rheological behavior of two crude oils and their surfactant-stabilized emulsions with initial droplet sizes ranging from 0.5 to 75 μm were investigated at various temperatures under steady and dynamic shear testing conditions. In order to evaluate the morphology and Stability of emulsions, microscopic analysis was carried out over three months and average diameter and size distribution of dispersed droplets were determined. The water content and surfactant concentration ranged from 10 to 60% vol/vol and 0.1 to 10% wt/vol, respectively. The results indicated that the rheological properties and the physical structure and stability of emulsions were significantly influenced by the water content... 

    Electroosmotic flow of viscoelastic fluids through a slit microchannel with a step change in wall temperature

    , Article Journal of Heat Transfer ; Volume 135, Issue 2 , 2013 ; 00221481 (ISSN) Sadeghi, A ; Veisi, H ; Saidi, M. H ; Asghar Mozafari, A ; Sharif University of Technology
    2013
    Abstract
    Thermally developing electroosmotically generated flow of two viscoelastic fluids, namely the PTT and FENE-P models, through a slit microchannel is considered. Both the viscous dissipation and Joule heating effects are taken into account and a step change in wall temperature is considered to represent physically conceivable thermal entrance conditions. Expressions for the dimensionless temperature and Nusselt number in the form of infinite series are presented. In general, the resultant eigenvalue problem is solved numerically; nevertheless, an analytical solution is presented for the regions close to the entrance. A parametric study reveals that increasing amounts of the Peclet number... 

    On the motion of Newtonian and non-Newtonian liquid drops

    , Article Scientia Iranica ; Volume 19, Issue 5 , 2012 , Pages 1265-1278 ; 10263098 (ISSN) Aminzadeh, M ; 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

    Thermal transport characteristics of non-newtonian electroosmotic flow in a slit microchannel

    , Article ASME 2011 9th International Conference on Nanochannels, Microchannels, and Minichannels, ICNMM 2011, 19 June 2011 through 22 June 2011 ; Volume 1 , June , 2011 , Pages 169-176 ; 9780791844632 (ISBN) Babaie, A ; Sadeghi, A ; Saidi, M. H ; Sharif University of Technology
    2011
    Abstract
    Electroosmosis has many applications in fluid delivery at microscale, sample collection, detection, mixing and separation of various biological and chemical species. In biological applications, most fluids are known to be non-Newtonian. Therefore, the study of thermal features of non-Newtonian electroosmotic flow is of great importance for scientific communities. In the present work, the fully developed electroosmotic flow of power-law fluids in a slit microchannel is investigated. The related equations are transformed into non-dimensional forms and necessary changes are made to adapt them for non-Newtonian fluids of power-law model. Results show that depending on different flow parameters... 

    DPD simulation of electroosmotic flow in nanochannels and the evaluation of effective parameters

    , Article 10th AIAA/ASME Joint Thermophysics and Heat Transfer Conference, 28 June 2010 through 1 July 2010, Chicago, IL ; 2010 ; 9781600867453 (ISBN) Darbandi, M ; Zakeri, R ; Schneider, G. E ; Sharif University of Technology
    2010
    Abstract
    We provide the simulation of electroosmotic phenomenon in nanochannels using the Dissipative Particle Dynamics (DPD) method. We study the electroosmotic phenomenon for both newtonian and non-newtonian fluids. Literature shows that most of past electroosmotic studies have been concentrated on continuum newtonian fluids. However, there are many nano/microfluidic applications, which need to be treated as either non-newtonian fluids or non-continuum fluids. In this paper, we simulate the electroosmotic flow in nanochannel considering no limit if it is neither continuum nor non-nonewtonian. As is known, the DPD method has several important advantages compared with the classical molecular dynamics... 

    Flow of a PTT fluid through planar contractions - Vortex inhibition using rounded corners

    , Article ASME 2010 International Mechanical Engineering Congress and Exposition, IMECE 2010, Vancouver, BC, 12 November 2010 through 18 November 2010 ; Volume 7, Issue PARTS A AND B , November , 2010 , Pages 601-607 ; 9780791844441 (ISBN) Khodadadi Yazdi, M ; Ramazani S. A, A ; Hosseini Amoli, H ; Behrang, A ; Kamyabi, A ; Sharif University of Technology
    2010
    Abstract
    Contraction flow is one of important geometries in fluid flow both in Newtonian and non-Newtonian fluids. In this study, flow of a viscoelastic fluid through a planar 4:1 contraction with rounded corners was investigated. Six different rounding ratios (RR =0, 0.125, 0.25, 0.375, 0.438, 0.475, 0.488) was examined using the linear PTT constitutive equation at creeping flow and isothermal condition. Then the resulting PDE set including continuity, momentum, and PTT constitutive equations were implemented to the OpenFOAM software. The results clearly show vortex deterioration with increasing rounding diameter, so that when rounding corner exceeds a critical value, the vortex disappears... 

    Analysis of non-newtonian fluids in microchannels with different wall materials

    , Article ASME 2009 7th International Conference on Nanochannels, Microchannels, and Minichannels ; 2009 , Pages 697-703 ; 9780791843499 (ISBN) Darbandi, M ; Behshad Shafii, M ; Safari Mohsenabad, S ; Sharif University of Technology
    Abstract
    The behavior of non-Newtonian fluids is considered as an important subject in micro scale and microfluidic flow researches. Because of the complexity and cost in the numerical works and the experimental set-ups in some instances, the analytical approach can be taken into account as a robust alternative tool to solve the non-Newtonian microfluidic flows in some special cases benefiting from a few simplified assumptions. In this work, we analyze the flow of two non-Newtonian fluids including the power-law and grade-fluid models in microchannels. For the grade-fluid, the stress tensors are defined considering the Rivlin-Ericksen tensor definitions. To avoid the complexities in the entrance... 

    Non-linear stress response of non-gap-spanning magnetic chains suspended in a newtonian fluid under oscillatory shear test: a direct numerical simulation

    , Article Physics of Fluids ; Volume 29, Issue 10 , 2017 ; 10706631 (ISSN) Hashemi, M. R ; Taghizadeh Manzari, M ; Fatehi, R ; Sharif University of Technology
    Abstract
    Adirect numerical simulation approach is used to investigate the effective non-linear viscoelastic stress response of non-gap-spanning magnetic chains suspended in a Newtonian fluid. The suspension is confined in a channel and the suspended clusters are formed under the influence of a constant external magnetic field. Large amplitude oscillatory shear (LAOS) tests are conducted to study the non-linear rheology of the system. The effect of inertia on the intensity of non-linearities is discussed for both magnetic and non-magnetic cases. By conducting magnetic sweep tests, the intensity and quality of the non-linear stress response are studied as a function of the strength of the external... 

    Drop formation from a capillary tube: comparison of different bulk fluid on newtonian drops and formation of newtonian and non-newtonian drops in air using image processing

    , Article International Journal of Heat and Mass Transfer ; Volume 124 , 2018 , Pages 912-919 ; 00179310 (ISSN) Nazari, A ; Zadkazemi Derakhshi, A ; Nazari, A ; Firoozabadi, B ; Sharif University of Technology
    Abstract
    The formation of water drops as a Newtonian fluid and formation of a shear-thinning non-Newtonian fluid, Carboxyl Methyl Cellulose (CMC) from a capillary into different bulk fluids are experimentally investigated. A high speed camera is used to visualize the images of the drops and an image-processing code employed to determine the drop properties from each image. It was found that the properties of the water drops when they are drooped into the liquids bulk fluids such as toluene and n-hexane are almost the same while they differed substantially when they were drooped into the air bulk fluid. It is shown that during the formation of water drop in all three kinds of bulk fluids, the drop... 

    Numerical investigation of blood flow. Part I: In microvessel bifurcations

    , Article Communications in Nonlinear Science and Numerical Simulation ; Volume 13, Issue 8 , 2008 , Pages 1615-1626 ; 10075704 (ISSN) Jafari, A ; Mousavi, S. M ; Kolari, P ; Sharif University of Technology
    2008
    Abstract
    In some diseases there is a focal pattern of velocity in regions of bifurcation, and thus the dynamics of bifurcation has been investigated in this work. A computational model of blood flow through branching geometries has been used to investigate the influence of bifurcation on blood flow distribution. The flow analysis applies the time-dependent, three-dimensional, incompressible Navier-Stokes equations for Newtonian fluids. The governing equations of mass and momentum conservation were solved to calculate the pressure and velocity fields. Movement of blood flow from an arteriole to a venule via a capillary has been simulated using the volume of fluid (VOF) method. The proposed simulation... 

    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) Vakilha, M ; 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...