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    An analytical solution for thermally fully developed combined pressure - electroosmotically driven flow in microchannels

    , Article International Journal of Heat and Mass Transfer ; Volume 50, Issue 5-6 , 2007 , Pages 1087-1096 ; 00179310 (ISSN) Qazi Zade, A ; Taghizadeh Manzari, M ; Hannani, S. K ; Sharif University of Technology
    2007
    Abstract
    An analytical solution is presented to study the heat transfer characteristics of the combined pressure - electroosmotically driven flow in planar microchannels. The physical model includes the Joule heating effect to predict the convective heat transfer coefficient in two dimensional microchannels. The velocity field, which is a function of external electrical field, electroosmotic mobility, fluid viscosity and the pressure gradient, is obtained by solving the hydrodynamically fully-developed laminar Navier-Stokes equations considering the electrokinetic body force for low wall zeta potentials. Then, assuming a thermally fully-developed flow, the temperature distribution and the Nusselt... 

    The effect of the time dependent pressure difference on bubble dynamics in microchannels

    , Article 4th International Conference on Nanochannels, Microchannels and Minichannels, ICNMM2006, Limerick, 19 June 2006 through 21 June 2006 ; Volume 2006 A , 2006 , Pages 83-88 ; 0791847608 (ISBN); 9780791847602 (ISBN) Keikhaee, A ; Rouhani, S ; Saboohi, Y ; Sharif University of Technology
    American Society of Mechanical Engineers  2006
    Abstract
    The physical processes responsible for bubble formation in microchannels are not well understood and lack fundamental understanding. Experimental results are not exactly in agreement with each other and there are no definite theories to explain the possible effects of different parameters. Among different parameters the microchannel hydraulic diameter can affect the bubble formation mechanism in microchannels strongly. In this paper the effect of the time dependent pressure difference between inside and outside of the bubble on bubble dynamics in microchannels have been investigated. The source of this time dependency can be the emergence of bubble embryos which produces a density... 

    Three-dimensional modeling of density current in confined and unconfined channels

    , Article 2006 ASME International Mechanical Engineering Congress and Exposition, IMECE2006, Chicago, IL, 5 November 2006 through 10 November 2006 ; 2006 ; 08888116 (ISSN); 0791837904 (ISBN); 9780791837900 (ISBN) Aram, E ; Firoozabadi, B ; Sharif University of Technology
    American Society of Mechanical Engineers (ASME)  2006
    Abstract
    Dense underflows are continuous currents which move down-slope due to the fact that their density is heavier than that ambient water. In this work, 2-D and 3-D density current in a channel were investigated by a set of experimental studies and the data were used to simulate the density current. The velocity components were measured using Acoustic Doppler Velocimetry (ADV). The height of density current (current's depth) was also measured. In this study, the density current with a uniform velocity and concentration enters the channel via a sluice gate into a lighter ambient fluid and moves forward down-slope. A low-Reynolds number turbulent model (Launder and Sharma, 1974) has been applied to... 

    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
    Abstract
    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... 

    3-D simulation of turbulent density

    , Article 2006 ASME Joint U.S.- European Fluids Engineering Division Summer Meeting, FEDSM2006, Miami, FL, 17 July 2006 through 20 July 2006 ; Volume 2 FORUMS , 2006 , Pages 361-367 ; 0791847500 (ISBN); 9780791847503 (ISBN) Hormozi, S ; Firoozabadi, B ; Ghasvari Jahromi, H ; Afshin, H ; Sharif University of Technology
    American Society of Mechanical Engineers  2006
    Abstract
    Density current is a dense fluid, which is continuously released from a source and spreads down a sloping surface inside a lighter, motionless fluid. A low-Reynolds number k-ε model (Launder and Sharma, 1974) has been used to simulate the behavior of 3-D density currents. Density current with a uniform velocity and concentration enters the channel via a sluice gate into a lighter ambient fluid and moves forward down-slope. The model has been verified with the experimental data sets. Although the k-ε Launder and Sharma model is applied here to a conservative density current, it seems the analysis is valid in general for turbidity current laden with fine particles. Copyright © 2006 by ASME  

    Numerical Analysis of Channel Flow over an Elastic Bump, Using Lattice Boltzmann Method- A Biological Application

    , M.Sc. Thesis Sharif University of Technology Rostami Gandomani, Saeed (Author) ; Taeibi Rahni, Mohammad (Supervisor)
    Abstract
    In recent years, lattice Boltzmann method (LBM) has been developed to be used as an alternative and promising computational technique to simulate various flows. It originates from classical statistical physics. The ability to simply solve complex flows, simulating of multiphase and multi-component without need to follow the boundaries of different phases, and the inherent ability of parallel processing are notable features of this approach. On the other hand, finite element method (FEM) is widely used in many practical engineering fields, especially in solid mechanics. In this study, in addition to simulating flow over a rigid body, flow over an elastic body is also simulated with a... 

    Triangular labyrinth side weirs with one and two cycles

    , Article Proceedings of the Institution of Civil Engineers: Water Management ; Volume 166, Issue 1 , 2013 , Pages 27-42 ; 17417589 (ISSN) Borghei, S. M ; Nekooie, M. A ; Sadeghian, H ; Ghazizadeh, M. R. J ; Sharif University of Technology
    2013
    Abstract
    Labyrinth side weirs provide a potentially effective way to shorten the length of a channel opening with the desired water height, but the discharge coefficient needs to be found experimentally. Experiments were carried out for triangular labyrinth side weirs with one and two cycles in order to obtain the discharge coefficient. The test variables included channel opening, head angle, number of cycles, weir height, upstream water depth and discharge in a subcritical situation. The resultsshow that the discharge coefficient ratio for a triangular labyrinth to a conventional side weir could rise to more than 2 with the same flow and geometric conditions. Relationships for the De Marchi... 

    Hydraulic behaviour of flow over an oblique weir

    , Article Journal of Hydraulic Research ; Volume 48, Issue 5 , 2010 , Pages 669-673 ; 00221686 (ISSN) Kabiri Samani, A ; Ansari, A ; Borghei, S. M ; Sharif University of Technology
    2010
    Abstract
    A comprehensive set of experiments was performed on weirs placed obliquely in a rectangular open channel. The main objectives were to investigate the effect of the weir angle relative to the approach flow direction on the behaviour and the hydraulic flow characteristics and to examine methods such as using upstream guide vanes and inclined aprons to increase the effective oblique weir length. Results indicate that by increasing the oblique angle, the effective length of the oblique weir increases significantly. Relationships are provided for the threshold submergence and the effective length of the oblique weir. Design recommendations are also presented for the use of guide vanes and... 

    Lateral dispersion in deflected emergent aquatic canopies

    , Article Environmental Fluid Mechanics ; Volume 19, Issue 4 , 2019 , Pages 833-850 ; 15677419 (ISSN) Jamali, M ; Davari, H ; Shoaei, F ; Sharif University of Technology
    Springer Netherlands  2019
    Abstract
    Understanding the mechanism of dispersion within plants is essential for proper operation of natural and constructed treatment wetlands. Plant deflection induced by the current drag modifies the flow and dispersion within an aquatic canopy. In this study, we look at the effect of the deflection angle of the plants on transverse dispersion. Experiments were carried out in a current flume on an array of inclined solid rods representing a deflected emergent canopy. The stem Reynolds number varied between 90 and 360, normalized stem densities between 0.011 and 0.033, and the inclination angles between 0° and 45°. The plume development was recorded using image processing technique. A special... 

    3D numerical analysis of joule heating effect on electroosmotic flow in microchannels

    , Article 4th International Conference on Nanochannels, Microchannels and Minichannels, ICNMM2006, Limerick, 19 June 2006 through 21 June 2006 ; Volume 2006 A , 2006 , Pages 203-208 ; 0791847608 (ISBN); 9780791847602 (ISBN) Monazami, R ; Yazdi, S ; Salehi, M. A ; Sharif University of Technology
    American Society of Mechanical Engineers  2006
    Abstract
    In this paper, a three-dimensional numerical model is developed to analyze the influence of the Joule heating on flow characteristics of an electroosmotic flow through square cross section micro-channels. The governing system of equations consists of three sets of equations: electric potential distribution, flow-field and energy equations. The solution procedure involves three steps. The net charge distribution on the cross section of the micro-channel 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... 

    Modification of standard k-epsilon turbulence model for multi-element airfoil application using optimization technique

    , Article 24th AIAA Applied Aerodynamics Conference, San Francisco, CA, 5 June 2006 through 8 June 2006 ; Volume 1 , 2006 , Pages 216-227 ; 10485953 (ISSN); 1563478129 (ISBN); 9781563478123 (ISBN) Darbandi, M ; Setayeshgar, A ; Vakili, S ; Schneider, G. E ; Sharif University of Technology
    American Institute of Aeronautics and Astronautics Inc  2006
    Abstract
    The use of multi-element airfoils has been known as a major approach to boost up the lift of wing without dramatic increase in its drag. In fact, the configuration helps to reduce the chance of flow separation over the airfoil. However, the use of a complicated geometry such as multi-element airfoil would normally cause complexity in flow behavior. The experience has shown that the flow field complexities cannot be properly modeled using standard two-equation k-epsilon turbulence model. Therefore, it is important to improve the accuracy of general turbulence models in specific applications and complex computational domains. In this work, we extend a suitable objective function based on... 

    Thermal transport in combined pressure - Electroosmotically driven flow in microchannels

    , Article 10th Intersociety Conference on Thermal and Thermomechanical Phenomena and Emerging Technologies in Electronic Systems, ITherm 2006, San Diego, CA, 30 May 2006 through 2 June 2006 ; Volume 2006 , 2006 , Pages 63-70 ; 0780395247 (ISBN); 9780780395244 (ISBN) Qazizade, A ; Taghizadeh Manzari, M ; Kazemzadeh Hannani, S ; Sharif University of Technology
    2006
    Abstract
    An analytical solution is presented to study the heat transfer characteristics of the combined pressure - electroosmotically driven flow in planar microchannels. The physical model includes the Joule heating effect to predict the convective heat transfer coefficient in two dimensional microchannels. The velocity field, which is a function of external electrical field, electroosmotic mobility, fluid viscosity and the pressure gradient, is obtained by solving the hydrodynamically fully-developed laminar Navier-Stokes equations considering the electrokinetic body force for low wall zeta potentials. Then, assuming a thermally fully-developed flow, the temperature distribution and the Nusselt... 

    Interfacial instabilities in sediment suspension flows

    , Article Journal of Fluid Mechanics ; Vol. 758, issue , November , 2014 , p. 312-326 Abedi, M ; Jalali, M. A ; Maleki, M ; Sharif University of Technology
    Abstract
    We report the existence of interfacial instability in the two-dimensional channel flow of a sediment suspension whose particles diffuse in the carrier fluid due to shear-induced collisions. We derive partial differential equations that govern the deformations of the interface between the sediment suspension and the clear fluid, and devise a perturbation method that preserves the positivity of the particle volume fraction. We solve perturbed momentum, particle transport and deforming interface equations to show that a Kelvin-Helmholtz-type unstable wave develops at the interface for wavelengths longer than a critical value. Short-wavelength oscillations of the interface are damped due to... 

    Three-dimensional modeling of density current in a straight channel

    , Article Journal of Hydraulic Engineering ; Volume 135, Issue 5 , 2009 , Pages 393-402 ; 07339429 (ISSN) Firoozabadi, B ; Afshin, H ; Aram, E ; Sharif University of Technology
    2009
    Abstract
    Dense underflows are continuous currents that move downslope due to their density being heavier than that of the ambient water. In this work, a steady density current with a uniform velocity and concentration from a narrow sluice gate enters into a wide channel of lighter ambient fluid and moves forward downslope. Experiments varying inlet velocity and concentration and hence inlet Richardson numbers were conducted. Numerical simulations were also performed with a low-Reynolds number k-ε model. The results of numerical simulation agree well with the experimental data. © 2009 ASCE  

    Generation of Voronoi grid based on vorticity for coarse-scale modeling of flow in heterogeneous formations

    , Article Transport in Porous Media ; Volume 83, Issue 3 , Oct , 2010 , Pages 541-572 ; 01693913 (ISSN) Evazi, M ; Mahani, H ; Sharif University of Technology
    2010
    Abstract
    We present a novel unstructured coarse grid generation technique based on vorticity for upscaling two-phase flow in permeable media. In the technique, the fineness of the gridblocks throughout the domain is determined by vorticity distribution such that where the larger is the vorticity at a region, the finer are the gridblocks at that region. Vorticity is obtained from single-phase flow on original fine grid, and is utilized to generate a background grid which stores spacing parameter, and is used to steer generation of triangular and finally Voronoi grids. This technique is applied to two channelized and heterogeneous models and two-phase flow simulations are performed on the generated... 

    Effect of temperature on microstructural evolution and subsequent enhancement of mechanical properties in a backward extruded magnesium alloy

    , Article International Journal of Advanced Manufacturing Technology ; 2017 , Pages 1-12 ; 02683768 (ISSN) Azimi, M ; Mirjavadi, S. S ; Salandari Rabori, A ; Sharif University of Technology
    Abstract
    The capability of backward extrusion (BE) method was assessed to achieve modified structures in AZ80 magnesium alloy. At first, 3D-Deform was employed to simulate the deformation flow through the deformed cup which gives an evidence from the flow behavior of the material. The material was processed via BE method at various temperatures of 250, 350, and 450 °C. Metallographic investigations were conducted in three different regions of the BE-processed cup (wall, bottom, and flow channel). The main feature observed at the wall of the BE cup was the presence of mechanical twins, the frequency of which was reduced by raising the process temperature. The flow localization in the form of shear... 

    Effect of temperature on microstructural evolution and subsequent enhancement of mechanical properties in a backward extruded magnesium alloy

    , Article International Journal of Advanced Manufacturing Technology ; Volume 95, Issue 9-12 , 2018 , Pages 3155-3166 ; 02683768 (ISSN) Azimi, M ; Mirjavadi, S. S ; Salandari-Rabori, A ; Sharif University of Technology
    Springer London  2018
    Abstract
    The capability of backward extrusion (BE) method was assessed to achieve modified structures in AZ80 magnesium alloy. At first, 3D-Deform was employed to simulate the deformation flow through the deformed cup which gives an evidence from the flow behavior of the material. The material was processed via BE method at various temperatures of 250, 350, and 450 °C. Metallographic investigations were conducted in three different regions of the BE-processed cup (wall, bottom, and flow channel). The main feature observed at the wall of the BE cup was the presence of mechanical twins, the frequency of which was reduced by raising the process temperature. The flow localization in the form of shear... 

    Solution of thermally developing zone in short micro-/nanoscale channels

    , Article Journal of Heat Transfer ; Volume 131, Issue 4 , 2009 , Pages 1-15 ; 00221481 (ISSN) Darbandi, M ; Vakilipour, S ; Sharif University of Technology
    2009
    Abstract
    We numerically solve the Navier-Stokes equations to study the rarefied gas flow in short micro-and nanoscale channels. The inlet boundary conditions play a critical role in the structure of flow in short channels. Contrary to the classical inlet boundary conditions, which apply uniform velocity and temperature profiles right at the real channel inlet, we apply the same inlet boundary conditions, but at a fictitious position far upstream of the real channel inlet. A constant wall temperature incorporated with suitable temperature jump is applied at the channel walls. Our solutions for both the classical and extended inlet boundary conditions are compared with the results of other available... 

    Fluid dynamics performance of bio -inspired flow channel design for bipolar plates in PEM fuel cells

    , Article 3rd European Fuel Cell Technology and Applications - Piero Lunghi Conference, EFC 2009, 15 December 2009 through 18 December 2009 ; 2009 , Pages 203-204 ; 9788882862114 (ISBN) Roshandel, R ; Karimi Moghaddam, G ; Barchiesi C ; Cigolotti V ; Chianella M ; McPhail S ; Lunghi P ; Sharif University of Technology
    ENEA  2009
    Abstract
    This study concentrates on the improvement in the performance of PEM fuel cells through optimization of the channel dimensions and patterns in the velocity and pressure fields in bipolar plates. For design and optimization purposes, a 2D numerical simulation of the flow distribution based on the Nervier-Stokes equations using individual computer code has been done. The outcome of the numerical simulations showed excellent agreement with the experimental results in previous works. Finally numerical simulation has been conducted to investigate the advantages of conventional patterns with inspiration from leaf flow pattern. It was found that both velocity and pressure fields are very uniform in... 

    Analytical solution of temperature field in micro-Poiseiulle flow with constant wall temperature

    , Article 6th International Conference on Nanochannels, Microchannels, and Minichannels, ICNMM2008, Darmstadt, 23 June 2008 through 25 June 2008 ; Issue PART B , 2008 , Pages 1371-1379 ; 0791848345 (ISBN); 9780791848340 (ISBN) Darbandi, M ; Safari Mohsenabad, S ; Vakilipour, S ; ASME ; Sharif University of Technology
    2008
    Abstract
    The analytical study of microchannels has been considered as a preliminary approach to alleviate the difficulties which are normally encountered in numerical and experimental studies. Among the analytical solutions, those with high robustness and low complexities are certainly more attractive. In this work, we present a theoretical approach to predict the temperature field in micro-Poiseuille channel flow with constant wall temperature. The use of power series method simplifies the solution in the current analytical approach. The current analytical derivations are examined for channels with both hot-wall and cold-wall conditions. The current solutions agree well with the numerical solutions...