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channel-flow
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Improvement of soil moisture and groundwater level estimations using a scale-consistent river parameterization for the coupled ParFlow-CLM hydrological model: A case study of the Upper Rhine Basin
, Article Journal of Hydrology ; Volume 610 , 2022 ; 00221694 (ISSN) ; Fahs, M ; Bitar, A. A ; Ataie Ashtiani, B ; Sharif University of Technology
Elsevier B.V
2022
Abstract
Accurate implementation of river interactions with subsurface water is critical in large-scale hydrologic models with a constant horizontal grid resolution when models apply kinematic wave approximation for both hillslope and river channel flow. The size of rivers can vary greatly in the model domain, and the implemented grid resolution is too coarse to accurately account for river interactions. Consequently, the flow velocity is underestimated when the width of the rivers is much narrower than the selected grid size. This leads to inaccuracy and uncertainties in calculations of water quantities. In addition, the rate of exfiltration and infiltration between the river and the subsurface may...
Casson fluid flow with heat and mass transfer in a channel using the differential transform method
, Article Kuwait Journal of Science ; Volume 49, Issue 1 , 2022 , Pages 1-19 ; 23074108 (ISSN) ; Ali, K ; Ashraf, M ; Sharif University of Technology
University of Kuwait
2022
Abstract
In the present investigation, we consider the heat and mass transfer characteristics of steady, incompressible and electrically conducting Casson fluid flow in a channel. The effect of chemical reactions have also been considered. The differential transform method (DTM) is applied to a system of non-linear ODEs, and the results are obtained in the form of DTM series. The principal gain of this approach is that it applies to the non-linear ODEs without requiring any discretization, linearization or perturbation. The velocity, mass and heat transfer profiles thus obtained are in good agreement with those provided by the quasi-linearization method (QLM). Graphical results for velocity,...
A numerical simulation to effectively assess impacts of flow channels characteristics on solid oxide fuel cell performance
, Article Energy Conversion and Management ; Volume 244 , 2021 ; 01968904 (ISSN) ; Adavi, K ; Sayyad Amin, J ; Zendehboudi, S ; Sharif University of Technology
Elsevier Ltd
2021
Abstract
Solid oxide fuel cells (SOFCs) introduce a promising electrochemical conversion technology to generate electricity directly from fuel oxidization. A three-dimensional (3D) numerical model is proposed to evaluate the SOFC performance by employing computational fluid dynamics (CFD) approach based on the finite element method. This research includes simultaneously solving momentum, energy, and mass transport equations linked with the electrochemical reactions. First, the modeling results of a SOFC system with a rectangular channel in the absence of obstacles are compared with the experimental data, showing very good agreement. The effects of different shapes and numbers of obstacles on fuel...
Effect of operating conditions on the performance of a PEM fuel cell
, Article International Journal of Heat and Mass Transfer ; Volume 144 , 2019 ; 00179310 (ISSN) ; Sharif University of Technology
Elsevier Ltd
2019
Abstract
In this study, a two-phase flow model based on species transport, energy, and electrochemical equations was developed for polymer electrolyte membrane fuel cell (PEMFC). The influences of heat sources and sinks, and water transport inside the fuel cell were also taken into account. In this regard, the effect of the operating conditions including cell temperature and pressure, anode and cathode inlet humidity, and anode and cathode stoichiometric ratios on the fuel cell performance was investigated. The simulation results show that inlet humidity and stoichiometric ratio of the anode side, cell pressure and temperature, and distribution of the heat sources and sinks are crucial factors...
Stress dependency of permeability, porosity and flow channels in anhydrite and carbonate rocks
, Article Journal of Natural Gas Science and Engineering ; Volume 70 , 2019 ; 18755100 (ISSN) ; Foroozesh, J ; Pourafshary, P ; Salmanpour, S ; Sharif University of Technology
Elsevier B.V
2019
Abstract
This study investigates the effect of stress magnitude and stress history on porosity and permeability values of anhydride and carbonate rocks. Porosity and permeability properties are measured for twelve anhydride and carbonate core samples under stress loading and unloading conditions. The results of permeability measurements show that tighter core samples are more stress dependent while the anhydride samples are generally more sensitive to the stress. The gap between stress loading and unloading (hysteresis) is more considerable at lower effective stress values. The results also indicate that the hysteresis is more noticeable in the anhydride core samples. The gas slippage factor is also...
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 three-dimensional incompressible flows in generalized curvilinear coordinates using a high-order compact finite-difference lattice boltzmann method
, Article International Journal for Numerical Methods in Fluids ; Volume 89, Issue 7 , 2019 , Pages 235-255 ; 02712091 (ISSN) ; Hejranfar, K ; Sharif University of Technology
John Wiley and Sons Ltd
2019
Abstract
In the present study, a high-order compact finite-difference lattice Boltzmann method is applied for accurately computing 3-D incompressible flows in the generalized curvilinear coordinates to handle practical and realistic geometries with curved boundaries and nonuniform grids. The incompressible form of the 3-D nineteen discrete velocity lattice Boltzmann method is transformed into the generalized curvilinear coordinates. Herein, a fourth-order compact finite-difference scheme and a fourth-order Runge-Kutta scheme are used for the discretization of the spatial derivatives and the temporal term, respectively, in the resulting 3-D nineteen discrete velocity lattice Boltzmann equation to...
Simulation of three-dimensional incompressible flows in generalized curvilinear coordinates using a high-order compact finite-difference lattice Boltzmann method
, Article International Journal for Numerical Methods in Fluids ; 2018 ; 02712091 (ISSN) ; Hejranfar, K ; Sharif University of Technology
John Wiley and Sons Ltd
2018
Abstract
In the present study, a high-order compact finite-difference lattice Boltzmann method is applied for accurately computing 3-D incompressible flows in the generalized curvilinear coordinates to handle practical and realistic geometries with curved boundaries and nonuniform grids. The incompressible form of the 3-D nineteen discrete velocity lattice Boltzmann method is transformed into the generalized curvilinear coordinates. Herein, a fourth-order compact finite-difference scheme and a fourth-order Runge-Kutta scheme are used for the discretization of the spatial derivatives and the temporal term, respectively, in the resulting 3-D nineteen discrete velocity lattice Boltzmann equation to...
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) ; 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...
Determination of discharge coefficient of triangular labyrinth side weirs with one and two cycles using the nonlinear PLS method
, Article Sustainable Hydraulics in the Era of Global Change - Proceedings of the 4th European Congress of the International Association of Hydroenvironment engineering and Research, IAHR 2016, 27 July 2016 through 29 July 2016 ; 2016 , Pages 653-657 ; 9781138029774 (ISBN) ; Parvaneh, A ; Kabiri Samani, A ; Sharif University of Technology
CRC Press/Balkema
2016
Abstract
Side weirs are hydraulic control structures widely used in irrigation, drainage networks and waste water treatment plants. These structures can be used for adjusting and diverting of flow with minimum energy loss. In spite of many studies were carried out on rectangular side weirs, the studies on oblique and labyrinth side weirs are scarce. In this study, based on the experimental data from more than 210 laboratory tests and through using the multivariable nonlinear partial least square (PLS) method, two nonlinear equations are presented for discharge coefficient CM of triangular labyrinth side weirs with one and two cycles. The obtained empirical equations relating CM with the relevant...
Pore-scale simulation of fluid flow passing over a porously covered square cylinder located at the middle of a channel, using a hybrid MRT-LBM–FVM approach
, Article Theoretical and Computational Fluid Dynamics ; Volume 29, Issue 3 , 2015 , Pages 171-191 ; 09354964 (ISSN) ; Taeibi Rahni, M ; Jam, F ; Sharif University of Technology
Springer New York LLC
2015
Abstract
A comprehensive study was performed to analyze the unsteady laminar flow characteristics around a porously covered, a fully porous, and a solid squared section cylinder located in the middle of a plane channel. In order to simulate fluid flow inside porous media and porous–fluid interface accurately (minimizing modeling error), the porous region was analyzed in pore scale, using LBM. Additionally, to minimize the LBM-related compressibility error through the porous region, a multi-block multiple relaxation time lattice Boltzmann method (MRT-LBM) was used. Also, to decrease CPU time, a Navier–Stokes flow solver, based on finite volume method and SIMPLE algorithm, was coupled with MRT-LBM to...
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) ; 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...
Long-lived and unstable modes of Brownian suspensions in microchannels
, Article Journal of Fluid Mechanics ; Volume 701 , 2012 , Pages 407-418 ; 00221120 (ISSN) ; Jalali, M. A ; Sharif University of Technology
2012
Abstract
We investigate the stability of the pressure-driven, low-Reynolds-number flow of Brownian suspensions with spherical particles in microchannels. We find two general families of stable/unstable modes: (i) degenerate modes with symmetric and antisymmetric patterns; (ii) single modes that are either symmetric or antisymmetric. The concentration profiles of degenerate modes have strong peaks near the channel walls, while single modes diminish there. Once excited, both families would be detectable through high-speed imaging. We find that unstable modes occur in concentrated suspensions whose velocity profiles are sufficiently flattened near the channel centreline. The patterns of growing unstable...
Simulation of an innovative flow-field design based on a bio inspired pattern for PEM fuel cells
, Article Renewable Energy ; Volume 41 , 2012 , Pages 86-95 ; 09601481 (ISSN) ; Arbabi, F ; Moghaddam, G. K ; Sharif University of Technology
2012
Abstract
Proton exchange membrane (PEM) fuel cell performance is directly related to the bipolar plate design and their channels pattern. Power enhancements can be achieved by optimal design of the type, size, or patterns of the channels. It has been realized that the bipolar plate design has significant role on reactant transport as well as water management in a PEM Fuel cell. Present work concentrates on improvements in the fuel cell performance by optimization of flow-field design and channels configurations. A three-dimensional, multi-component numerical model of flow distribution based on Navier-Stokes equations using individual computer code is presented. The simulation results showed excellent...
An innovative three dimensional numerical model for bipolar plates to enhance the efficiency of PEM fuel cells
, Article ASME 2012 10th International Conference on Fuel Cell Science, Engineering and Technology Collocated with the ASME 2012 6th International Conference on Energy Sustainability, FUELCELL 2012, 23 July 2012 through 26 July 2012 ; July , 2012 , Pages 351-360 ; 9780791844823 (ISBN) ; Roshandel, R ; Sharif University of Technology
American Society of Mechanical Engineers (ASME)
2012
Abstract
The efficiency of proton exchange membrane (PEM) fuel cell is straightly correlated to the bipolar plate design and fluid channel arrangements. Higher produced energy can be attained by optimal design of type, size, or patterns of the channels. Previous researches showed that the bipolar plate channel design has a considerable effect on reactant distribution uniformity as well as humidity control in PEM fuel cells. This paper concentrates on enhancements in the fuel cell performance by optimization of bipolar plate design and channels configurations. A numerical model of flow distribution based on Navier-Stokes equations using individual computer code is presented. The results gained from...
Experiments on turbidity current regimes in a straight open channel
, Article World Environmental and Water Resources Congress 2011: Bearing Knowledge for Sustainability - Proceedings of the 2011 World Environmental and Water Resources Congress, 22 May 2011 through 26 May 2011 ; May , 2011 , Pages 4047-4064 ; 9780784411735 (ISBN) ; Ayyoubzadeh, S. A ; Firoozabadi, B ; Kordi, E ; Sharif University of Technology
2011
Abstract
The present study has been conducted to investigate the effect of inlet flow regimes on vertical velocity and concentration profiles of the turbidity current. Experiments carried out on small scale channel and Kaolin with a density of 2.65 kg/m3 and a mean particle diameter of 4.5 μm, was used to generate the currents. Velocities were obtained at a rate of 10 Hz using an acoustic Doppler velocimeter. Using the siphon sampling approach, the acoustic backscattering intensity was calibrated and concentration was determined using a backscattering analysis. Results showed that the ratio of maximum velocity height to the height of the current was around 0.4-0.5 in sub- and super-critical regimes....
Hydraulic behaviour of flow over an oblique weir
, Article Journal of Hydraulic Research ; Volume 48, Issue 5 , 2010 , Pages 669-673 ; 00221686 (ISSN) ; 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...
Local scour at open-channel junctions
, Article Journal of Hydraulic Research ; Volume 48, Issue 4 , Sep , 2010 , Pages 538-542 ; 00221686 (ISSN) ; Jabbari Sahebari, A ; Sharif University of Technology
2010
Abstract
High bed-shear stress resulting from secondary flows and velocity increase at a channel junction cause local erosion and deposition in natural rivers and earth-lined channels. Herein, the scour patterns at the junction of two loose bed channels were studied under clear-water conditions. The main dimensionless variables are the angle between the two approach flow branches, the discharge and width ratios of the tributary to the downstream channel branches, and the ratio of the mean downstream velocity to the threshold velocity. The results indicate that the position of the maximum scour depth temporally moves to the outer wall and upstream to the main channel, as affected by the dimensionless...
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) ; 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 a standing baffle on the flow structure in a rectangular open channel
, Article Journal of Hydraulic Research ; Volume 48, Issue 3 , Jun , 2010 , Pages 400-404 ; 00221686 (ISSN) ; Takeda, Y ; Firoozabadi, B ; Sharif University of Technology
2010
Abstract
The effect of an intermediate standing baffle on the flow structure in a rectangular open channel has been investigated by a three-dimensional acoustic Doppler velocimeter. Investigation of time-averaged velocity profiles at different streamwise positions reveals that the approach flow is fully developed upstream of the baffle. By analysing the space-averaged power spectra of streamwise velocity, a peak structure was observed in the upstream baffle region. Downstream of the baffle this peak structure has been alleviated by the baffle. The same analysis for the vertical component indicates the existence of a peak structure both up- and downstream of the baffle. Consequently, a baffle affects...