Search for: microchannel
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    Hydrodynamic dispersion by electroosmotic flow of viscoelastic fluids within a slit microchannel

    , Article Microfluidics and Nanofluidics ; Volume 22, Issue 1 , January , 2018 ; 16134982 (ISSN) Hoshyargar, V ; Talebi, M ; Ashrafizadeh, S. N ; Sadeghi, A ; Sharif University of Technology
    Springer Verlag  2018
    The biofluids being manipulated in lab-on-a-chip devices usually contain elastic macromolecules. Accordingly, for an accurate modeling of the relevant flow physics one should invoke viscoelastic constitutive equations. In this paper, attention is paid toward the hydrodynamic dispersion by the fully developed electroosmotic flow of PTT viscoelastic fluids in slit microchannels of low zeta potential. Adopting the Taylor–Aris approach, analytical solutions are derived for late-time solute concentration and effective dispersion coefficient. Finite element-based numerical simulations are also conducted to monitor the broadening of an analyte band from the moment of injection. Both approaches are... 

    Numerical investigation of thermal performance augmentation of nanofluid flow in microchannel heat sinks by using of novel nozzle structure: sinusoidal cavities and rectangular ribs

    , Article Journal of the Brazilian Society of Mechanical Sciences and Engineering ; Volume 41, Issue 10 , 2019 ; 16785878 (ISSN) Khodabandeh, E ; Akbari, O. A ; Toghraie, D ; Pour, M. S ; Jönsson, P. G ; Ersson, M ; Sharif University of Technology
    Springer Verlag  2019
    In this paper, we present a numerical simulation of a laminar, steady and Newtonian flow of f-graphene nanoplatelet/water nanofluid in a new microchannel design with factors for increasing heat transfer such as presence of ribs, curves to enable satisfactory fluid mixing and changing fluid course at the inlet and exit sections. The results of this study show that Nusselt number is dependent on nanoparticles concentration, inlet geometry and Reynolds number. As the nanofluid concentration increases from 0 to 0.1% and Reynolds number from 50 to 1000, the Nusselt number enhances nearly up to 3% for increase in fluid concentration and averagely from 15.45 to 54.1 and from 14.5 to 55.9 for... 

    A new non-dimensional parameter to obtain the minimum mixing length in tree-like concentration gradient generators

    , Article Chemical Engineering Science ; Volume 195 , 2019 , Pages 120-126 ; 00092509 (ISSN) Rismanian, M ; Saidi, M. S ; Kashaninejad, N ; Sharif University of Technology
    Elsevier Ltd  2019
    Microfluidic-based concentration gradient generators (CGGs) have a number of applications in chemical, biological and pharmaceutical studies. Thus, precise design of the microfluidic system is crucial to maintaining the desired concentration gradient in microchannels. One of the design considerations is the length of microchannels in the structure of a CGG. A CGG with a short length fails to provide the complete diffusive mixing, while the size of the microchip would unfavorably increase by incorporating a long CGG. Considering a CGG as a tree-like structure consisting of T-shaped micromixers, the mixing process of the species at a straight microchannel has been solved analytically. Herein,... 

    Numerical investigation on the effect of external varying magnetic field on the mixing of ferrofluid with deionized water inside a microchannel for lab-on-chip systems

    , Article Energy Sources, Part A: Recovery, Utilization and Environmental Effects ; 2020 Saadat, M ; Ghassemi, M ; Shafii, M. B ; Sharif University of Technology
    Taylor and Francis Inc  2020
    Energy-efficient mixing is vital for chemical and fuel processes. To this end, a flow-focusing configuration is proposed to investigate the effect of a uniform magnetic field on the mixing of a water-based ferrofluid with two streams of deionized water. An external and varying magnetic field is imposed on a straight microchannel, and the mixing between the ferrofluid and deionized waters is qualitatively and quantitatively measured. A commercial code based on the finite-element method is used, and the simulations are validated by two experimental studies in the literature. For a magnetic flux density of 10 mT, a signal frequency of 1 Hz, a duty cycle of 0.3, an inlet velocity of 500 µm/s,... 

    Secondary flows, mixing, and chemical reaction analysis of droplet-based flow inside serpentine microchannels with different cross sections

    , Article Langmuir ; Volume 37, Issue 17 , 2021 , Pages 5118-5130 ; 07437463 (ISSN) Ghazimirsaeed, E ; Madadelahi, M ; Dizani, M ; Shamloo, A ; Sharif University of Technology
    American Chemical Society  2021
    Chemical bioreactions are an important aspect of many recent microfluidic devices, and their applications in biomedical science have been growing worldwide. Droplet-based microreactors are among the attractive types of unit operations, which utilize droplets for enhancement in both mixing and chemical reactions. In the present study, a finite-volume-method (FVM) numerical investigation is conducted based on the volume-of-fluid (VOF) applying for the droplet-based flows. This multiphase computational modeling is used for the study of the chemical reaction and mixing phenomenon inside a serpentine microchannel and explores the effects of the aspect ratio (i.e., AR = height/width) of... 

    Numerical Simulation of Turbulent Flow Heat Transfer in the Entrance Region of Microchannels

    , M.Sc. Thesis Sharif University of Technology Sadeghi, Arman (Author) ; Nouri Borujerdi, Ali (Supervisor)
    In this thesis the steady state convective heat transfer for turbulent, two-dimensional, incompressible gas flow in a circular microchannel under slip flow and temperature jump conditions is numerically investigated by means of finite volume scheme. The low Reynolds number k-ε turbulence model is employed using a new boundary condition for turbulent kinetic energy at solid surface. To calculate variables at control volume surfaces in the axial direction upwind differencing scheme and in the radial direction central differencing scheme are used. Rhie-Chow interpolation technique is used to prevent pressure field oscillations. The set of discrete equations are solved using SIMPLE Algorithm. In... 

    Simulating Flow over Nanoparticles through Microchannels Using Lattice Boltzmann Method

    , M.Sc. Thesis Sharif University of Technology Setayeshgar, Alireza (Author) ; Darbandi, Masoud (Supervisor)
    Novel manufacturing technologies in micro scales, such as micro machining, guide us through constructing micro scale systems known as MEMS. These systems have a wide range of applications, from fabrication of electrostatic, magnetic, pneumatic sensors and actuators to micro mechanical gears and motors. Also, MEMS applications involve the manipulation of one or more fluids, known as microfluids. Simulation of flow through microchannels over nano particles has important applications in solid particles transport. In this flow, the rarefaction phenomenon will affect the flow behavior and its subsequent impacts such as aerodynamic drag forces. In this work, we use the Lattice Boltzmann method... 

    Fabrication of Ferrofluidic Micropump

    , M.Sc. Thesis Sharif University of Technology Ashouri, Majid (Author) ; Shafii, Mohammad Behshad (Supervisor) ; Saidi, Mohammad Said (Supervisor) ; Saidi, Mohammad Hassan (Supervisor)
    In this project, two Ferrofluidic micropumps that do not need any mechanical moving parts are presented. These micropumps are including simple microchannels containing magnetic fluid plugs that are used as flow actuator and the on/off valve. Using external magnetic field actuation in this type of micropumps, the magnetic fluid would have continuous motion in a channel with micrometer dimensions that would provide the main fluid to be pumped. Although the plug of magnetic fluid has surface contact with operative fluid, but considering its specific features, it would not compine with the pumping fluid. These micropumps may be used to pump the fluids or gases. The outcomes of the investigation... 

    Heat Transfer in Uniform Suction Porous Media of Micro Channel with Variable Cross-section

    , M.Sc. Thesis Sharif University of Technology Akrami, Hamid Reza (Author) ; Nouri Borujerdi, Ali (Supervisor) ; Kazemzadeh Hannani, Siamak (Supervisor)
    Fully developed fluid flow and heat transfer is numerically investigated in micro-channels. There are many techniques to intensify heat transfer for internal flows, such as: increasing Reynolds number, extending surface area of channel wall and also disrupting the boundary layer thickness on the wall. Among these, extension wall surface area is a common technique. There are several ways to extend surface area including finned, slotted, chemically etched, grooved as well as porous media adhered wall surface. One other method that we work on it is modifying wall cross-section and usage of uniform suction porous media. The governing equations include the momentum equation of the core region... 

    Novel boundary condition implementation to model electroosmotic phenomenon in microchannels

    , Article Proceedings of the 7th International Conference on Nanochannels, Microchannels, and Minichannels 2009, ICNMM2009, 22 June 2009 through 24 June 2009, Pohang ; Issue PART A , 2009 , Pages 243-251 ; 9780791843499 (ISBN) Darbandi, M ; Farzinpour, P ; Sharif University of Technology
    This Paper presents simulation of Electroosmotic phenomenon in a capillary using an extended hybrid finite-volume-element method. Most of the last electroosmotic phenomenon studies in microchannels do not take into consideration the effect of reservoirs and pressure drops occurred at the inlet and outlet of the microchannel. This neglect may lead to a few drawbacks. For example, the incorrect pressure drops can significantly alter the flow patterns and mass flow rates in microchannels. As a remedy the use of reservoirs at the two ends of a microchannel has been recently practiced as a novel strategy to overcome this drawback. However, this remedy needs careful attention because the resulting... 

    3D numerical analysis of velocity profiles of PD, EO and combined PD-EO flows through microchannels

    , Article 4th International Conference on Nanochannels, Microchannels and Minichannels, ICNMM2006, Limerick, 19 June 2006 through 21 June 2006 ; Volume 2006 A , 2006 , Pages 209-214 ; 0791847608 (ISBN); 9780791847602 (ISBN) Yazdi, S ; Monazami, R ; Salehi, M. A ; Sharif University of Technology
    American Society of Mechanical Engineers  2006
    In this paper, a three-dimensional numerical model is developed to analyze flow characteristics of pressure driven, electroosmotic and combined pressure driven-electroosmotic flows through micro-channels. The governing system of equations consists of the electric-field and flow-field equations. The solution procedure involves three steps. The net charge distribution on the cross section of the microchannel is computed by solving two-dimensional Poisson-Boltzmann equation using the finite element method. Then, using the computed fluid's charge distribution, the magnitude of the resulting body force due to interaction of an external electric field with the charged fluid is calculated along the... 

    Development of a consistent slip boundary condition at the inlet of microchannels

    , Article 44th AIAA Aerospace Sciences Meeting 2006, Reno, NV, 9 January 2006 through 12 January 2006 ; Volume 10 , 2006 , Pages 7087-7096 ; 1563478072 (ISBN); 9781563478079 (ISBN) Darbandi, M ; Vakilipour, S ; Schneider, G. E ; Sharif University of Technology
    The fast progress in Microelectromechanical systems has drawn the attention of many numerical workers to provide sufficient numerical tools to analyze the micro flows accurately. Besides many ambiguities behind the slip boundary condition research which are normally encountered in the vicinity of the solid walls (and are necessary to provide the suitable bridge between the macro and micro behaviors), there are serious uncertainties at the inlet of channels where the microflow enters into the conduit. Indeed, the macro inlet flow have been long investigated by the past workers; however, there is little effort to clarify the issue in micro inlet flow cases. In this research, we utilize the... 

    A novel mechanism for heat transfer enhancement through microchannels using electrokinetic effect

    , Article 2005 ASME Summer Heat Transfer Conference, HT 2005, San Francisco, CA, 17 July 2005 through 22 July 2005 ; Volume 3 , 2005 , Pages 949-955 ; 0791847314 (ISBN); 9780791847312 (ISBN) Qazi Zade, A ; Manzari, M. T ; Monazami, R ; Bazargan, V ; Sharif University of Technology
    In this paper a three-dimensional numerical model is developed in order to study the heat transfer enhancement in rectangular microchannels due to electrokinetic effect. The electrokinetic body force on fluid elements gives some superior convective transport properties to the flow relative to pure pressure driven flow in microchannels. Unlike the conventional parabolic velocity profile of pressure driven laminar flow, the electrokinetic body force transforms the velocity profile to a slug-like flow. Due to sharp velocity gradient near the wall, the convective heat transfer properties of the flow are improved dramatically. Net charge distribution across the channel is obtained by solving the... 

    Design and fabrication of a two-phase diamond nanoparticle aided fast PCR device

    , Article Analytica Chimica Acta ; Volume 1068 , 2019 , Pages 28-40 ; 00032670 (ISSN) Madadelahi, M ; Ghazimirsaeed, E ; Shamloo, A ; Sharif University of Technology
    Elsevier B.V  2019
    Polymerase Chain Reaction (PCR) is an important and prevalent technique in biotechnology because of its crucial role in cloning DNA fragments and diagnostic applications. In the present study, a high-throughput two-phase PCR device is designed and fabricated which utilizes a serpentine microchannel together with a spiral structure. The former is for the droplet-generation and mixing and the latter is for the thermal cycling process. Moreover, the effect of diamond nanoparticles (diamondNP) on the performance of PCR is also investigated while using commercial PCR devices and the fabricated PCR device designed in this study. Using numerical simulation, it is shown that within the simple and... 

    Variational formulation on Joule heating in combined electroosmotic and pressure driven microflows

    , Article International Journal of Heat and Mass Transfer ; Volume 61, Issue 1 , June , 2013 , Pages 254-265 ; 00179310 (ISSN) Sadeghi, A ; Saidi, M. H ; Waezi, Z ; Chakraborty, S ; Sharif University of Technology
    The present study attempts to analyze the extended Graetz problem in combined electroosmotic and pressure driven flows in rectangular microchannels, by employing a variational formulation. Both the Joule heating and axial conduction effects are taken into consideration. Since assuming a uniform inlet temperature profile is not consistent with the existence of these effects, a step change in wall temperature is considered to represent physically conceivable thermal entrance conditions. The method of analysis considered here is primarily analytical, in which series solutions are presented for the electrical potential, velocity, and temperature. For general treatment of the eigenvalue problem... 

    Microfluidic Tensiometry and Investigation of Nanoparticles Adsorption at Liquid/Liquid Interfaces

    , M.Sc. Thesis Sharif University of Technology Arvahi, Milad (Author) ; Mohammadi, Ali Asghar (Supervisor)
    The present paper is an attempt to critically measure interfacial tension with microchannels and achieve the quantity of adsorption in the liquid – liquid interfaces and comparing the adsorption of surfactants and nanoparticles surface modificated as well. At this point we need to make emulsion and it is necessary for droplets to be monodispersed due to analyze these droplets in this paper. According to this condition for our droplets microsystems are the best options. As we know surfactants were already known as a stabilizing emulsion agent and in this paper nanoparticles are suggested as suitable alternatives for surfactants which can be absorbed as if they are in the water / oil... 

    Design and Fabrication of a Spiral Microchannel for High Resolution Blood Cell Separation

    , M.Sc. Thesis Sharif University of Technology Mehran, Amir Hossein (Author) ; Saeedi, Mohammad Saeed (Supervisor) ; Taghipoor, Mojtaba (Co-Supervisor)
    In medical science, preparing a high purity sample of certain kinds of cells plays an important role in studying the characteristics and functionality of cells, detecting in vitro harmful pathogens and helping to find ways of preventing and treating diseases that cause cellular disorders in the human body. The goal of this research is to improve the spiral microchannel with stair-like cross section in order to separate white blood cells from whole blood. First, the efficiency of this method was evaluated numerically, using a developed finite element model. Then, the desired microchannel mold was made using the micromiling method, and we fabricated the chip using soft lithography and pasting... 

    A ¬High Order Accurate Numerical Solution of Incompressible Slip Flow in Microchannels with Heat Transfer by Using Artificial Compressibility Method

    , M.Sc. Thesis Sharif University of Technology Mohafez, Mir Hamed (Author) ; Hejranfar, Kazem (Supervisor)
    In the present study, a high-order accurate numerical solution of steady incompressible slip flow and heat transfer in 2D microchannels is presented. The numerical method used is an alternating direction implicit operator scheme which is efficiently implemented to solve the incompressible Navier-Stokes equations in the primitive variables formulation using the artificial compressibility method. To stabilize the numerical solution, numerical filters are used. The present methodology considers the solution of the Navier-Stokes equations with¬ employing different slip boundary condition¬¬ (Maxwell,¬ ¬¬Hyperbolic tangent function of Knudsen number¬ and Beskok slip models)¬ ¬¬on the wall to model... 

    Simulation of two-Dimensional Supersonic Flow in Slip Regime in Microchannel with Finite Difference Lattice Boltzmann Method

    , M.Sc. Thesis Sharif University of Technology Barootiha, Hamed (Author) ; Hejranfar, Kazem (Supervisor)
    In this study, the simulation of two-dimensional supersonic flows through microchannels in slip flow regime is performed using a lattice Boltzmann model (LBM). Traditional LB models have been used to simulate incompressible fluid flows and there are not suitable for modeling compressible or thermo-fluid flows. Herein, a recently developed LB model, namely, the finite difference lattice Boltzmann method (FDLBM), is employed to simulate compressible flows with embedded shocks. In this model, one can select particle velocities independently from the lattice configuration, and therefore, a correct and numerically stable multispeed thermal model by adopting more isotropic particle velocities can... 

    Simulation of Flow and Mass Transfer in Microfluidic Systems of Human Body

    , Ph.D. Dissertation Sharif University of Technology Saadatmand, Maryam (Author) ; Abd Khodaei, Mohammad Jafar (Supervisor) ; Farhadi, Fathollah (Supervisor) ; Pishvaie, Mahmoud Reza (Supervisor)
    The effects of gravity and inertia dominate our experiences of the physical world. But as systems are reduced in size, phenomena such as diffusion, surface tension and viscosity become ever more important; at the microscale they can dominate and result in a world that operates very differently from the macroscopic world. Kidney is one of the vital organs in which fluid and mass transfer occur between blood flow in microvessels and urine in microchannels called nephron. The present work is aimed at applying microchannel theory to study renal system. First, a n efficient numerical orthogonal collocation method has been employed to solve the steady-state formulation of electrolyte transport in...