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flow-hydrodynamics
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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) ; 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...
Electric-field-induced response of a droplet embedded in a polyelectrolyte gel
, Article Physics of Fluids ; Volume 25, Issue 8 , 2013 ; 10706631 (ISSN) ; 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...
Simulation and Experimental Study of Permeability Reduction in Porous Media Due to Mud Filtrate Invasion Under Dynamic Conditions
, Ph.D. Dissertation Sharif University of Technology ; Jamshidi, Saeed (Supervisor)
Abstract
The reduction of the effective permeability of the reservoir rock in the production area due to various factors is called formation damage. Formation damage is always one of the topics discussed in petroleum engineering. Among the primary and important cases that lead to damage to the formation are the filtration of drilling mud into the production area and the deposition of colloidal particles inside the porous rock during the drilling operation. The length of the productive zone in contact with the drilling fluid usually reaches several hundred feet in Iranian formations. In this study, the aim is to more accurately estimate the amount of permeability reduction caused by the penetration of...
Laminar falling film flow of aqueous Li Br solution on a horizontal elliptical tube
, Article International Journal of Fluid Mechanics Research ; Volume 40, Issue 4 , 2013 , Pages 324-343 ; 10642277 (ISSN) ; Saidi, M. H ; Sharif University of Technology
2013
Abstract
Flow hydrodynamics of laminar falling film of aqueous Li Br solution (Li Br - H2O) on a horizontal elliptical tube has been investigated in this research. The film velocity distribution and film thickness, namely, the flow characteristics are determined by solving analytically simultaneous simplified Navier - Stokes equations and continuity equation in polar and Cartesian coordinates. The analysis is based on steady state laminar flow of falling liquid film of Li Br - H2O on a horizontal elliptical tube in polar model and Cartesian model (CM), for cases in which traction on the film surface is considered negligible. Models are compared with each other in three cases of aspect ratios (Ar),...
Simulating fluid-solid interaction problems using an immersed boundary-SPH method
, Article Particle-Based Methods II - Fundamentals and Applications, 26 October 2011 through 28 October 2011 ; Octobe , 2011 , Pages 954-965 ; 9788489925670 (ISBN) ; Fatehi, R ; Manzari, M. T ; Sharif University of Technology
Abstract
In this work, the Immersed Boundary Method (IBM) is adapted and implemented in the context of Smoothed Particle Hydrodynamics (SPH) method to study moving solid bodies in an incompressible fluid flow. The proposed computational algorithm is verified by solving a number of benchmark particulate flow problems. The results are also compared with those obtained using the same SPH scheme along with a direct solid boundary imposition technique
Towards an understanding of the marine fouling effects on VIV of circular cylinders: Response of cylinders with regular pyramidal roughness
, Article Applied Ocean Research ; Volume 59 , 2016 , Pages 378-394 ; 01411187 (ISSN) ; Bakhtiari, A ; Ehteshami, M ; Seif, M. S ; Sharif University of Technology
Elsevier Ltd
2016
Abstract
Underwater surface of man-made structures is quickly covered by unwanted aquatic organisms. They change the flow regime around the structure. Despite the important contributions of previous studies on the vortex induced vibration (VIV) of bluff bodies, the flow induced vibration of non-stationary cylinders covered by marine fouling appears not to have received due attentions in the literature. The current paper reports on an attempt for better understanding the marine fouling effects on the VIV of circular cylinders. A structured review of the literature related to the fluid structure interactions in marine fouled cylinders is first presented. Results of an experimental study on the VIV of...
Solute dispersion by electroosmotic flow through soft microchannels
, Article Sensors and Actuators, B: Chemical ; Volume 255, Part 3 , February , 2018 , Pages 3585-3600 ; 09254005 (ISSN) ; Khorami, A ; Ashrafizadeh, S. N ; Sadeghi, A ; Sharif University of Technology
Elsevier B.V
2018
Abstract
We study the hydrodynamic dispersion (HD) by electroosmotic flow in soft microchannels. Considering a fully developed flow in a slit microchannel of low surface potential and adopting the Taylor dispersion theory, we derive analytical solutions for the solute concentration field and the effective dispersion coefficient. We also conduct numerical analyses to broaden the paper's scope to high surface potentials and to specify a criterion for the validity of the Debye-Hückel linearization in soft microconduits as well as to investigate the broadening of an analyte band from the time of injection. It is demonstrated that the effective dispersion coefficient of a neutral solute band is generally...
Hydrodynamic dispersion by electroosmotic flow of viscoelastic fluids within a slit microchannel
, Article Microfluidics and Nanofluidics ; Volume 22, Issue 1 , January , 2018 ; 16134982 (ISSN) ; Talebi, M ; Ashrafizadeh, S. N ; Sadeghi, A ; Sharif University of Technology
Springer Verlag
2018
Abstract
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...
Computer simulation of flocs interactions: Application in fiber suspension
, Article Colloids and Surfaces A: Physicochemical and Engineering Aspects ; Volume 292, Issue 2-3 , 2007 , Pages 99-109 ; 09277757 (ISSN) ; Zamankhan, P ; Mousavi, S. M ; Sharif University of Technology
Elsevier
2007
Abstract
The present effort is the development of a multiscale modeling, simulation methodology for investigating complex phenomena arising from flowing fiber suspensions. Specific consideration was given to dynamic simulations of viscoelastic fibers in which the fluid flow is predicted by a method that is a hybrid between Direct Numerical Simulations (DNS) and Large Eddy Simulation techniques (LES), and fluid fibrous structure interactions (FSI) will be taken into account. Numerical results are presented for which focus is on fiber floc deformation by hydrodynamic forces in turbulent flows. Dynamics of simple fiber networks in a shearing flow of water in a channel flow illustrate that the...
Investigation of flow dynamics in porous media using computer simulation
, Article 20th European Simulation and Modelling Conference, ESM 2006, Toulouse, 23 October 2006 through 25 October 2006 ; 2006 , Pages 157-163 ; Zamankhan, P ; Mousavi, S. M ; Pietarinen, K ; Sarkomaa, P ; Sharif University of Technology
EUROSIS
2006
Abstract
The aim of this work is to investigate flow hydrodynamics in porous media. Random non-overlapping spherical particles in a cylindrical geometry were produced as a porous media. Navier-Stokes equations in three-dimensional porous packed bed have been solved and dimensionless pressure drop has been studied for a fluid flow through the porous media at different Reynolds numbers (based on pore permeability and interstitial fluid velocity). The numerical results are in good agreement with those reported by Macdonald (1979) in the range of Reynolds numbers studied. At higher Reynolds numbers turbulent models such as large eddy simulation (LES) and Reynolds stress model (RSM) also have been...
A truly incompressible smoothed particle hydrodynamics based on artificial compressibility method
, Article Computer Physics Communications ; Volume 210s , 2017 , Pages 10-28 ; 00104655 (ISSN) ; Hejranfar, K ; Sharif University of Technology
Abstract
In the present study, a truly incompressible smoothed particle hydrodynamics based on the artificial compressibility method for simulating steady and unsteady incompressible flows is proposed and assessed. The incompressible Navier–Stokes equations in the primitive variables formulation using the artificial compressibility method proposed by Chorin in the Eulerian reference frame are written in a Lagrangian reference frame to provide an appropriate incompressible SPH algorithm. The proposed SPH formulation implemented here is based on an implicit dual-time stepping scheme to be capable of time-accurate analysis of unsteady flows. The advantage of the Artificial Compressibility-based...
CFD simulation of gas–solid flow patterns in a downscaled combustor-style FCC regenerator
, Article Particuology ; Volume 39 , 2018 , Pages 96-108 ; 16742001 (ISSN) ; Behjat, Y ; Safekordi, A. A ; Sharif University of Technology
Elsevier B.V
2018
Abstract
To investigate the gas–solid flow pattern of a combustor-style fluid catalytic cracking regenerator, a laboratory-scale regenerator was designed. In scaling down from an actual regenerator, large-diameter hydrodynamic effects were taken into consideration. These considerations are the novelties of the present study. Applying the Eulerian–Eulerian approach, a three-dimensional computational fluid dynamics (CFD) model of the regenerator was developed. Using this model, various aspects of the hydrodynamic behavior that are potentially effective in catalyst regeneration were investigated. The CFD simulation results show that at various sections the gas–solid flow patterns exhibit different...
An efficient system identification approach to estimate unsteady loads on cavitator plates
, Article Ocean Engineering ; Volume 207 , 2020 ; Dehghani Firouz Abadi, R ; Sharif University of Technology
Elsevier Ltd
2020
Abstract
A new and efficient model for calculation of the unsteady hydrodynamic loads on an oscillating plate in two-dimensional flow is proposed. In order to compute the hydrodynamic loads, an unsteady hydrodynamic model is derived using the boundary-element method along with the potential flow assumption. To this aim, the steady boundary of cavity is determined by a full-nonlinear iterative procedure. Thereafter, assuming that amplitude and frequency of oscillations are so that the length of cavity in unsteady flow remains intact, simulation of the unsteady hydrodynamic flow is performed by imposing some velocity perturbations over the steady cavity solutions. Consequently, based on this...
Mathematical modeling of a slurry reactor for DME direct synthesis from syngas
, Article Journal of Natural Gas Chemistry ; Volume 21, Issue 2 , March , 2012 , Pages 148-157 ; 10039953 (ISSN) ; Kazemeini, M ; Fattahi, M ; Sharif University of Technology
2012
Abstract
In this paper, an axial dispersion mathematical model is developed to simulate a three-phase slurry bubble column reactor for direct synthesis of dimethyl ether (DME) from syngas. This large-scale reactor is modeled using mass and energy balances, catalyst sedimentation and single-bubble as well as two-bubbles class flow hydrodynamics. A comparison between the two hydrodynamic models through pilot plant experimental data from the literature shows that heterogeneous two-bubbles flow model is in better agreement with the experimental data than homogeneous single-bubble gas flow model. Also, by investigating the heterogeneous gas flow and axial dispersion model for small bubbles as well as the...
Compound triple jets film cooling improvements via velocity and density ratios: Large eddy simulation
, Article Journal of Fluids Engineering, Transactions of the ASME ; Volume 133, Issue 3 , Mar , 2011 ; 00982202 (ISSN) ; Ramezanizadeh, M ; Taeibi Rahni, M ; Salimi, M ; Sharif University of Technology
2011
Abstract
The flow hydrodynamic effects and film cooling effectiveness placing two small coolant ports just upstream the main jet (combined triple jets) were numerically investigated. Cross sections of all jets are rectangular and they are inclined normally into the hot cross-flow. The finite volume method and the SIMPLE algorithm on a multiblock nonuniform staggered grid were applied. The large-eddy simulation approach with three different subgrid scale models was used. The obtained results showed that this flow configuration reduces the mixing between the freestream and the coolant jets and hence provides considerable improvements in film cooling effectiveness (both centerline and spanwise averaged...
Intelligent regime recognition in upward vertical gas-liquid two phase flow using neural network techniques
, Article American Society of Mechanical Engineers, Fluids Engineering Division (Publication) FEDSM, 1 August 2010 through 5 August 2010, Montreal, QC ; Volume 2 , 2010 , Pages 293-302 ; 08888116 (ISSN) ; 9780791849491 (ISBN) ; Hanafizadeh, P ; Saidi, M. H ; Bozorgmehry Boozarjomehry, R ; Sharif University of Technology
2010
Abstract
In order to safe design and optimize performance of some industrial systems, it's often needed to categorize two-phase flow into different regimes. In each flow regime, flow conditions have similar geometric and hydrodynamic characteristics. Traditionally, flow regime identification was carried out by flow visualization or instrumental indicators. In this research3 kind of neural networks have been used to predict system characteristic and flow regime, and results of them were compared: radial basis function neural networks, self organized and Multilayer perceptrons (supervised) neural networks. The data bank contains experimental pressure signalfor a wide range of operational conditions in...
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...