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dispersion-coefficient
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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) ; 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...
Investigating the Dispersion Phenomenon in Fluid Flow through Porous Media Using Percolation Theory
, M.Sc. Thesis Sharif University of Technology ; Masihi, Mohsen (Supervisor) ; Ganjeh Ghazvini, Mostafa (Co-Advisor)
Abstract
Many processes in the petroleum engineering industry involve particle transport in oil and gas reservoirs including sand production, fines migration, and nanoparticle injection. In these processes it is important to understand where the particles are travelling in the reservoir and the impact that they have on the formation properties. Large particles can damage the formation and decrease permeability which reduces the productive capacity of the reservoir. During nanoparticle injection, forces at the pore level can cause retention of particles and prevent their recovery. In addition, due to the heterogeneity of typical reservoirs, it is difficult to predict how particles will spread across...
The Experimental Investigation of Lateral Dispersion In Vegetated Flow
, M.Sc. Thesis Sharif University of Technology ; Jamali, Mirmosadegh (Supervisor)
Abstract
There is an importance issue for preservation and survival of ecological systems by vegetation. A study focusing on the hydrodynamics of these complex ecosystems could help to explain the filtering ability of vegetation in wetlands and estuaries. Wetlands assist in flood control, shoreline protection, and groundwater recharge.In addition, they play a purification role, removing sediments and contaminants from polluted waters, nutrient uptake, and oxygen production. Laboratory experiments have been designed to study the influence of marsh vegetation on lateral dispersion. The flow through vegetation is modeled by a circulating flow going through an array of plastic dowels in an experimental...
, M.Sc. Thesis Sharif University of Technology ; Jamali, Mirmossadegh (Supervisor)
Abstract
Preservation and survival of ecological systems by vegetation is important. A study focusing on the hydrodynamics of these complex ecosystems could help to explain the filtering ability of vegetation in wetlands and estuaries. Wetlands assist in flood control, shoreline protection, and groundwater recharge. In addition, they play a purification role in removing sediments and contaminants from polluted waters, nutrient uptake, and oxygen production.
Laboratory experiments have been designed to study the influence of marsh vegetation on lateral dispersion in flexible vegetation that has been modelled with inclined cylinder. The flow through vegetation is modelled by a circulating flow...
Laboratory experiments have been designed to study the influence of marsh vegetation on lateral dispersion in flexible vegetation that has been modelled with inclined cylinder. The flow through vegetation is modelled by a circulating flow...
Lateral dispersion in deflected emergent aquatic canopies
, Article Environmental Fluid Mechanics ; Volume 19, Issue 4 , 2019 , Pages 833-850 ; 15677419 (ISSN) ; 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...
Simulation of fluid flow through a granular bed
, Article 8th Biennial ASME Conference on Engineering Systems Design and Analysis, ESDA2006, Torino, 4 July 2006 through 7 July 2006 ; Volume 2006 , 2006 ; 0791837793 (ISBN); 9780791837795 (ISBN) ; Mousavi, S. M ; Sharif University of Technology
American Society of Mechanical Engineers
2006
Abstract
Numerical study of flow through random packing of non-overlapping spheres in a cylindrical geometry is investigated. Dimensionless pressure drop has been studied for a fluid through the porous media at moderate Reynolds numbers (based on pore permeability and interstitial fluid velocity), and numerical solution of Navier-Stokes equations in three dimensional porous packed bed illustrated in excellent agreement with those reported by Macdonald [1979] in the range of Reynolds number studied. The results compare to the previous work (Soleymani et al., 2002) show more accurate conclusion because the problem of channeling in a duct geometry. By injection of solute into the system, the...
Interaction of Nonlinear pulses for Nondestructive Characterization of the Highly Nonlinear Fiber
, Ph.D. Dissertation Sharif University of Technology ; Mehrani, Khashayar (Supervisor)
Abstract
In this thesis, while a comprehensive study of different methods for the characterization of the optical fibers is done, a unique and effective method is being introduced for the characterization of the dispersion coefficient of Highly Nonlinear Fibers (HNLFs). The proposed method is based on the Brillouin Optical Time Domain Analysis (BOTDA) of a wave generated by the Four Wave Mixing (FWM) interaction. The current method, which includes an experimental scheme and an algorithm for solving the inverse problem, offers high sensitivity and experimental accuracy at the longitudinal resolution of 1 meter. The noise level has been considerably reduced by understanding different sources of the...
Experimental Study of Effects of Resonance on Transverse Dispersion in Aquatic Vegetation
, M.Sc. Thesis Sharif University of Technology ; Jamali, Mirmosadegh (Supervisor)
Abstract
The purpose of this research is to investigate the movement and diffusion of pollution transversely around a set of stems of flexible plants with different materials and to observe the effect of resonance on lateral dispersion. Two stem samples of polyurethane and nylon were used under different Reynolds numbers. Vertically uniform dye is injected into the flow, and the evolution of the dye plume along the flow is measured using image processing. By measuring the displacements of selected stems we study the effects of resonance on stem vibration and lateral dispersion. The experiments were also conducted for no-stem dispersion and the results were compared with those with plant samples. The...
Comparison of Lateral Dispersion in Flexible and Semi-Rigid Emergent Aquatic Canopies with Staggered, Random, and In-Line Arrangements
, M.Sc. Thesis Sharif University of Technology ; Jamali, Mirmosadegh (Supervisor)
Abstract
Hydrodynamics of flow is affected by physical and biological interactions between flow and aquatic vegetation. This study represents the role of array distribution on lateral dispersion in emergent aquatic vegetation using two flexible and semi-rigid models. Experiments were carried out with three different arrangements, including random, staggered, and in-line. The Reynolds numbers at the stem scale ranged from 120 to 690, and the stem densities were 1% and 1.44%. Furthermore, the effects of stem flexibility and, specifically, stem resonance on lateral dispersion were examined. An image processing technique was used to measure plume width and calculate lateral dispersion. It was found that...
Dispersion compensation using high-positive dispersive optical fibers
, Article Chinese Optics Letters ; Volume 15, Issue 3 , 2017 ; 16717694 (ISSN) ; Marvasti, F ; Pakravan, M. R ; Sharif University of Technology
Science Press
2017
Abstract
The common and traditional method for optical dispersion compensation is concatenating the transmitting optical fiber by a compensating optical fiber having a high-negative dispersion coefficient. In this Letter, we take the opposite direction and show how an optical fiber with a high-positive dispersion coefficient is used for dispersion compensation. Our optical dispersion compensating structure is the optical implementation of an iterative algorithm in signal processing. The proposed dispersion compensating system is constructed by cascading a number of compensating sub-systems, and its compensation capability is improved by increasing the number of embedded sub-systems. We also show that...
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...
Experimental study of lateral dispersion in flexible aquatic canopy with emergent blade-like stems
, Article Physics of Fluids ; Volume 32, Issue 6 , 25 June , 2020 ; Sehat, H ; Sharif University of Technology
American Institute of Physics Inc
2020
Abstract
This paper quantitatively investigates the role of flexibility of blade-like stems and, in particular, the occurrence of stem resonance on lateral dispersion in emergent aquatic canopies. Two sets of experiments are presented: single-stem and canopy tests. In the first set, the flow around single blade-like flexible model stems and the proximity to a resonant state are studied. Wake areas behind four model stems with distinct flexibilities are measured by particle image velocimetry for stem Reynolds numbers between 350 and 850. A single flexible emergent stem bends and oscillates in in-line and cross-flow directions due to periodic forcing associated with the vortex shedding. The plant...
Statistical model of dispersion in a 2-D glass micromodel
, Article 16th SPE/DOE Improved Oil Recovery Symposium 2008 - ""IOR: Now More Than Ever."", Tulsa, OK, 19 April 2008 through 23 April 2008 ; Volume 2 , 2008 , Pages 527-539 ; 9781605601656 (ISBN) ; Kharrat, R ; Rashtchian, D ; Vossoughi, S ; Sharif University of Technology
Society of Petroleum Engineers (SPE)
2008
Abstract
Microscopic Visualization of the porous media can provide valuable information to enhance understanding of pore-scale transport phenomena. Here, a micromodel which its grains and pores are non-uniform in size, shape and distribution is considered as porous medium. The pore size distribution as well as pore length distribution was extracted by applying an image analysis technique. A two-dimensional random network model of the micromodel has been constructed which the nonuniformity is considered by assigning measured distribution functions. The random particle method was applied for correlating and predicting dispersion coefficients based on probabilistic approaches. Statistical derivations...
Numerical investigations of fluid flow and lateral fluid dispersion in bounded granular beds in a cylindrical coordinates system
, Article Chemical Engineering and Technology ; Volume 30, Issue 10 , 2007 , Pages 1369-1375 ; 09307516 (ISSN) ; Turunen, I ; Yousefi, H ; Bastani, D ; Sharif University of Technology
2007
Abstract
Results are presented from a numerical study examining the flow of a viscous, incompressible fluid through a random packing of non-overlapping spheres at moderate Reynolds numbers, spanning a wide range of flow conditions for porous media. By using a laminar model including inertial terms and assuming rough walls, numerical solutions of the Navier-Stokes equations in three-dimensional porous packed beds resulted in dimensionless pressure drops in excellent agreement with those reported in a previous study. This observation suggests that no transition to turbulence could occur in the range of the Reynolds number studied. For flows in the Forchheimer regime, numerical results are presented of...
Dispersion around a circular cylinder in surface wave motion
, Article Scientia Iranica ; Vol. 21, issue. 3 , 2014 , p. 548-556 ; 10263098 ; Jamali, M ; Sharif University of Technology
Abstract
In this paper, we examine fluid flow and associated dispersion around a circular cylinder under progressive surface wave motion. The flow field and vortex shedding patterns were studied using flow visualization and Particle Image Velocimetry (PIV). Several patterns of vortex shedding were identified around a single cylinder. The vortex shedding patterns under progressive wave motion are similar to those observed in planar oscillatory flow, except in the way the vortices form and in the orientation they take. The observed vortex patterns in progressive wave motion are more unstable than those in planar oscillatory flow. Using particle tracking and the Lagrangian dispersion method, the...
Statistical model for dispersion in a 2D glass micromodel
, Article SPE Journal ; Volume 15, Issue 2 , 2010 , Pages 301-312 ; 1086055X (ISSN) ; Kharrat, R ; Rashtchian, D ; Vossoughi, S ; Sharif University of Technology
2010
Abstract
Microscopic visualization of a porous medium can provide valuable information to enhance understanding of pore-scale transport phenomena. In this work, a novel and unique approach is provided to combine experimentally measured pore-size distribution with theoretical statistical analysis to predict longitudinal and transverse dispersion coefficients. The approach presented can be easily extended to predict other fluid-flow parameters through porous media, such as permeability, and capillary pressure. Here, a micromodel is considered as a porous medium. The grains and pores of the micromodel are nonuniform in size, shape, and distribution. The pore-size distribution, as well as pore-length...
Study of the effect of thermal dispersion on internal natural convection in porous media using fourier series
, Article Transport in Porous Media ; Volume 131, Issue 2 , 2020 , Pages 537-568 ; Graf, T ; Tran, T. V ; Ataie Ashtiani, B ; Simmons, C. T ; Younes, A ; Sharif University of Technology
Springer
2020
Abstract
Natural convection in a porous enclosure in the presence of thermal dispersion is investigated. The Fourier–Galerkin (FG) spectral element method is adapted to solve the coupled equations of Darcy’s flow and heat transfer with a full velocity-dependent dispersion tensor, employing the stream function formulation. A sound implementation of the FG method is developed to obtain accurate solutions within affordable computational costs. In the spectral space, the stream function is expressed analytically in terms of temperature, and the spectral system is solved using temperature as the primary unknown. The FG method is compared to finite element solutions obtained using an in-house code...
Effect of distance-dependent dispersivity on density-driven flow in porous media
, Article Journal of Hydrology ; Volume 589 , October , 2020 ; Fahs, M ; Ataie Ashtiani, B ; Simmons, C. T ; Sharif University of Technology
Elsevier B.V
2020
Abstract
In this study, the effect of distance-dependent dispersion coefficients on density-driven flow is investigated. The linear asymptotic model, which assumes that dispersivities increase linearly with distance from the source of contamination and reach asymptotic values at a large asymptotic distance, is employed. An in-house numerical model is adapted to handle distance-dependent dispersion. The effect of asymptotic-dispersion on aquifer contamination is analyzed for two tests: (i) a seawater intrusion problem in a coastal aquifer and (ii) a leachate transport problem from a surface deposit site. Global Sensitivity Analysis (GSA) combined with the Polynomial Chaos Expansion (PCE) surrogate...
Effect of gas impurity on the convective dissolution of CO2 in porous media
, Article Energy ; Volume 199 , May , 2020 ; Amooie, M. A ; Rostami, B ; Bahrami, F ; Sharif University of Technology
Elsevier Ltd
2020
Abstract
Growing needs for energy and the essential role of fossil fuels in energy market require attempts such as carbon dioxide (CO2) sequestration in saline aquifers to stabilize and mitigate atmospheric carbon concentrations. The possibility of co-injection of impurities along with CO2 allows for the direct disposal of flue gas and hence a significant reduction in the cost of CO2 sequestration projects by eliminating the separation process. In this study, the results of series of novel experiments in a high-pressure visual porous cell are reported, which allow for visually and quantitatively examining the dynamics of convective dissolution in brine-saturated porous media in the presence of an...
Unsteady solute dispersion by electrokinetic flow in a polyelectrolyte layer-grafted rectangular microchannel with wall absorption
, Article Journal of Fluid Mechanics ; Volume 887 , 2020 ; Saidi, M. H ; Moosavi, A ; Sadeghi, A ; Sharif University of Technology
Cambridge University Press
2020
Abstract
The dispersion of a neutral solute band by electrokinetic flow in polyelectrolyte layer (PEL)-grafted rectangular/slit microchannels is theoretically studied. The flow is assumed to be both steady and fully developed and a first-order irreversible reaction is considered at the wall to account for probable surface adsorption of solutes. Considering low electric potentials, analytical solutions are obtained for electric potential, fluid velocity and solute concentration. Special solutions are also obtained for the case without wall adsorption. To track the dispersion properties of the solute band, the generalized dispersion model is adopted by considering the exchange, the convection and the...