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Analytical dual mesh method for two-phase flow through highly heterogeneous porous media
, Article Journal of Hydrology ; Volume 400, Issue 1-2 , 2011 , Pages 195-205 ; 00221694 (ISSN) ; Firoozabadi, B ; Rashtchian, D ; Ashjari, M. A ; Sharif University of Technology
2011
Abstract
Detailed geological models of a reservoir may contain many more cells that can be handled by reservoir simulators due to computer hardware limitations. Upscaling is introduced as an effective way to overcome this problem. However, recovery predictions performed on a coarser upscaled mesh are inevitably less accurate than those performed on the initial fine mesh. Dual mesh method is an approach that uses both coarse and fine grid information during simulation. In the reconstruction step of this method, the equations should be solved numerically within each coarse block, which is a time consuming process. Recently, a new coarse-grid generation technique based on the vorticity preservation...
Vorticity-based coarse grid generation for upscaling two-phase displacements in porous media
, Article Journal of Petroleum Science and Engineering ; Volume 59, Issue 3-4 , 2007 , Pages 271-288 ; 09204105 (ISSN) ; Firoozabadi, B ; Mahani, H ; Khoozan, D ; Sharif University of Technology
2007
Abstract
Coarse grid generation from finely gridded geological model is a main step in reservoir simulation. Coarse grid generation algorithms aim at optimizing size, number and location of the grid blocks by identifying the important geological and flow features which control flow in porous media. By optimizing coarse grid structure we can improve accuracy of the coarse scale simulation results to reproduce fine grid behavior. A number of techniques have been proposed in the literature. We present a novel coarse grid generation procedure based on vorticity preservation between fine and coarse grids. In the procedure, the coarse grid mesh tries to capture variations in both permeability and fluid...
A priori error estimation of upscaled coarse grids for water-flooding process
, Article Canadian Journal of Chemical Engineering ; Volume 94, Issue 8 , 2016 , Pages 1612-1626 ; 00084034 (ISSN) ; Firoozabadi, B ; Sharif University of Technology
Wiley-Liss Inc
2016
Abstract
Advanced reservoir characterization methods can yield geological models at a very fine resolution, containing 1011–1018 cells, while the common reservoir simulators can only handle much lower numbers of cells due to computer hardware limitations. The process of coarsening a fine-scale model to a simulation model is known as upscaling. Predicting the accuracy of simulation results over an upscaled grid with respect to the fine grid is highly important, as it can yield the optimum upscaling process. In this paper, permeability-based and velocity-based a priori error estimation techniques are proposed by introducing image processing-based comparison methods in the context of upscaling. The...
Optimization-based upscaling for two-phase flow through porous media: Structured grid generation
, Article Transport in Porous Media ; Volume 108, Issue 3 , July , 2015 , Pages 617-648 ; 01693913 (ISSN) ; Firoozabadi, B ; Sharif University of Technology
Kluwer Academic Publishers
2015
Abstract
The process of coarsening the detailed geological model of a reservoir to simulation models is known as upscaling. There are two fundamental steps in the procedure of upscaling, i.e., defining the coarse grid geometry and calculating the average properties for the generated coarse grid. In this paper, the focus will be on investigating the applicability of optimization in the context of coarse grid geometry definition. To do so, different objective function candidates will be defined, and their behavior in terms of predicting the two-phase flow accuracy of coarse grids will be analyzed to determine the proper objective function. A modified objective function employing the idea of analytical...
Upscaling and Simulation of Two-Phase Flow in Porous Media
, Ph.D. Dissertation Sharif University of Technology ; Firoozabadi, Bahar (Supervisor)
Abstract
Advanced reservoir characterization methods can yield geological models at a very fine resolution, containing 1011-1018 cells while the common reservoir simulators can handle much fewer numbers of cells due to computer hardware limitations. The process of coarsening the fine-scale model to simulation models is known as upscaling. There are three fundamental steps in the procedure of upscaling, i.e. defining the coarse grid geometry, calculating the average properties for the generated coarse grid and simulation of the two-phase flow equations on the generated coarse-scale model. In this thesis, the focus will be on investigating the applicability of optimization in the context of coarse grid...
Data science and predictive analytics : biomedical and health applications using R
, Book
Springer International Publishing AG
2018
Synergistic effect of MEHPA on co-extraction of zinc and cadmium with DEHPA
, Article Minerals Engineering ; Volume 17, Issue 1 , 2004 , Pages 89-92 ; 08926875 (ISSN) ; Moradkhani, D ; Darvishi, D ; Askari, M ; Behnian, D ; Sharif University of Technology
2004
Abstract
Simultaneous extraction of zinc and cadmium by a mixture of di-2-ethyl hexyl phosphoric acid (DEHPA) and mono-2-ethyl hexyl phosphoric acid (MEHPA), and the synergistic effect of MEHPA on co-extraction of zinc and cadmium with DEHPA have been investigated. It was shown that the extraction of zinc and cadmium by DEHPA and/or MEHPA can be increased by an increase of pH. The results also illustrate that the pH0.5 of zinc, by increase in MEHPA from 0.1 to 8 vol%, did not vary significantly while that of cadmium varies from 0.63 to 2.4. In other words MEHPA prevents selective extraction of zinc from aqueous media containing both zinc and cadmium. Studies on the selective separation parameter...
Investigating the convective flow of ternary hybrid nanofluids and single nanofluids around a stretched cylinder: Parameter analysis and performance enhancement
, Article International Journal of Thermofluids ; Volume 23 , 2024 ; 26662027 (ISSN) ; Hosseinzadeh, K ; Ganji, D. D ; Sharif University of Technology
2024
Abstract
Within this research, we examined the convective flow of a blend of ternary hybrid nanofluids and single nanofluids with a stagnation point caused by a stretched cylinder. The purpose of this study is to investigate the effect of using a ternary hybrid nanofluid instead of a single nanofluid. Water is used as the base fluid in this investigation. The single nanofluid is made of copper and the ternary hybrid nanofluid is made of Molybdenum disulfide, copper, and silver. The impact of the curvature parameter, nanoparticle volume fraction, mixed convection parameter, velocity ratio, shape factor, conjugate number and Eckert number parameters on temperature and velocity profiles has been...
MHD flow in a channel using new combination of order of magnitude technique and HPM [MHD tok u kanalu uporabom novih kombinacija tehnika grubog opisa vrijednosti i HPM]
, Article Tehnicki Vjesnik ; Volume 21, Issue 2 , April , 2014 , Pages 317-321 ; ISSN: 13303651 ; Ganji, D. D ; Rahni, M. T ; Sharif University of Technology
2014
Abstract
The present work is concerned with the steady incompressible flow through a parallel plate channel with stretching walls under an externally applied magnetic field. The governing continuity and Navier-Stokes equations are reduced to a fourth order nonlinear differential equation by using vorticity definition and similarity solution transformation. The obtained equations are solved by applying the analytical homotopy perturbation method (HPM). The method is called order of magnitude suggested for simplifying series solution to finite expression that is useful in engineering problems. The results are verified by comparing with numerical solutions and demonstrate a good accuracy of the obtained...
Analytical solution of nonlinear differential equations two oscillators mechanism using Akbari-Ganji method
, Article Modern Physics Letters B ; Volume 35, Issue 31 , 2021 ; 02179849 (ISSN) ; Hosseinzadeh, K ; Rahai, M ; Ganji, D. D ; Sharif University of Technology
World Scientific
2021
Abstract
In the last decade, many potent analytical methods have been utilized to find the approximate solution of nonlinear differential equations. Some of these methods are energy balance method (EBM), homotopy perturbation method (HPM), variational iteration method (VIM), amplitude frequency formulation (AFF), and max-min approach (MMA). Besides the methods mentioned above, the Akbari-Ganji method (AGM) is a highly efficient analytical method to solve a wide range of nonlinear equations, including heat transfer, mass transfer, and vibration problems. In this study, it was constructed the approximate analytic solution for movement of two mechanical oscillators by employing the AGM. In the derived...
A compiler for multi-key homomorphic signatures for Turing machines
, Article Theoretical Computer Science ; Volume 889 , 2021 , Pages 145-170 ; 03043975 (ISSN) ; Fiore, D ; Venturi, D ; Amini, M ; Sharif University of Technology
Elsevier B.V
2021
Abstract
At SCN 2018, Fiore and Pagnin proposed a generic compiler (called “Matrioska”) allowing to transform sufficiently expressive single-key homomorphic signatures (SKHSs) into multi-key homomorphic signatures (MKHSs) under falsifiable assumptions in the standard model. Matrioska is designed for homomorphic signatures that support programs represented as circuits. The MKHS schemes obtained through Matrioska support the evaluation and verification of arbitrary circuits over data signed from multiple users, but they require the underlying SKHS scheme to work with circuits whose size is exponential in the number of users, and thus can only support a constant number of users. In this work, we propose...
Ride comfort of high-speed trains travelling over railway bridges
, Article Vehicle System Dynamics ; Volume 43, Issue 3 , 2005 , Pages 173-197 ; 00423114 (ISSN) ; Younesian, D ; Thompson, D ; Jones, C ; Sharif University of Technology
Taylor and Francis Ltd
2005
Abstract
The ride comfort of high-speed trains passing over railway bridges is studied in this paper. A parametric study is carried out using a time domain model. The effects of some design parameters are investigated such as damping and stiffness of the suspension system and also ballast stiffness. The influence of the track irregularity and train speed on two comfort indicators, namely Sperling's comfort index and the maximum acceleration level are also studied. Two types of railway bridges, a simple girder and an elastically supported bridge are considered. Timoshenko beam theory is used for modelling the rail and bridge and two layers of parallel damped springs in conjunction with a layer of mass...
Entropy generation analysis of kerosene oil flow with ternary hybrid nanoparticles on the stretchable exponential surface
, Article International Journal of Modelling and Simulation ; 2024 ; 02286203 (ISSN) ; Hosseinzadeh, K ; Najafpour, A ; Ganji, D. D ; Sharif University of Technology
2024
Abstract
In this research, the flow of kerosene oil with ternary hybrid nanoparticles on a stretchable exponential surface has been investigated. There is also a discussion about the entropy analysis of the flow of hydromagnetic radiation by the surface. The ternary hybrid nanofluid (THyNF) contains graphene oxide (GO), magnesium oxide (MgO), and zinc oxide (ZnO) as nanoparticles and kerosene oil as a base fluid. Using useful transformations, differential equations with partial derivatives (PDEs) were transformed into ordinary differential equations (ODEs). Then, the ODEs were solved using the RK5th method. Furthermore, the impacts of parameters like radiation parameter ((Formula presented.)),...
The investigation of pre-ionization effect on the improvement of pinch quality and increased hard X-ray radiation in a dense plasma focus (DPF) device
, Article Journal of Fusion Energy ; Volume 43, Issue 1 , 2024 ; 01640313 (ISSN) ; Vosoughi, N ; Mahabadi, T. D ; Piriaei, D ; Sharif University of Technology
2024
Abstract
This study delves into the impact of the pre-ionization technique, facilitated by an optimal shunt resistor, on a DPF device operating with deuterium gas. The investigation unveils enhancements in critical parameters within the plasma column environment during the pinch phase, specifically the total and plasmoid hard x-ray yields. Employing a combination of time-resolved detectors, such as plastic scintillator and magnetic probe arrays, alongside time-integrated detectors like pinhole camera, and just by using this technique, the research illustrated an augmented plasma sheath velocity during the axial phase. Notably and other than the enhancement of hard x-ray yield, the optimal pressure of...
Heat transfer hybrid nanofluid (1-Butanol/MoS2–Fe3O4) through a wavy porous cavity and its optimization
, Article International Journal of Numerical Methods for Heat and Fluid Flow ; 2020 ; Montazer, E ; Shafii, M. B ; Ganji, D. D ; Sharif University of Technology
Emerald Group Holdings Ltd
2020
Abstract
Purpose: The purpose of this paper is to investigate natural convection in a porous wavy-walled enclosure that is including a cylinder cavity in the middle of it and filled with a hybrid nanofluid contains 1-Butanol as the base fluid and MoS2–Fe3O4 hybrid nanoparticles. Design/methodology/approach: The domain of interest is bounded by constant temperature horizontal corrugated surfaces and isothermal vertical flat surfaces. The numerical outputs are explained in the type of isotherms, streamline and average Nusselt number with variations of the Rayleigh number, Hartmann number, nanoparticle shape factor and porosity of the porous medium. For solving the governing equations, the finite...
Detection of ammonia gas by knudsen thermal force in micro gas actuator
, Article Case Studies in Thermal Engineering ; Volume 12 , 2018 , Pages 276-284 ; 2214157X (ISSN) ; Barzegar Gerdroodbary, M ; Mosavat, M ; Ganji, D. D ; Sharif University of Technology
2018
Abstract
Direct Simulation Monte Carlo (DSMC) method is applied to evaluate the performance of a new micro gas sensor (MIKRA) for mass analysis of ammonia in the rarefied gas. In order to simulate a rarefied gas inside the micro gas detector, Boltzmann equation is applied to obtain high precision results. This study performed comprehensive studies to reveal the main mechanism of force generation and applied this for the analysis of the gas mixture. Our findings show that value of generated Knudsen force significantly varies when the percentage of the NH3 varies in the mixture. According to obtained results, the maximum Knudsen force increases when the fraction of the ammonia decreases. Our findings...
Dual-phase-lag thermoelastic damping in nonlocal rectangular nanoplates
, Article Waves in Random and Complex Media ; Volume 34, Issue 1 , 2024 , Pages 162-181 ; 17455030 (ISSN) ; Cheng, D ; Cong, G ; Jin, D ; Borjalilou, V ; Sharif University of Technology
2024
Abstract
The present article pertains to the assessment of thermoelastic damping (TED) in rectangular nanoplates by incorporation of size effect within the constitutive and heat conduction relations. With the purpose of establishing size-dependent coupled thermoelastic equations, nonlocal elasticity theory and dual-phase-lag heat conduction model are utilized. By considering time-harmonic vibrations, nonclassical frequency equation affected by thermoelastic coupling is derived. By solving this equation and extracting the real and imaginary parts of damped natural frequency via some mathematical operations, an explicit expression for description of TED in circular nanoplates is obtained. With the goal...
Hydrothermal assessment of a double-pass shell and tube heat exchanger in the presence of blade turbulators with different configurations
, Article International Journal of Thermofluids ; Volume 21 , Volume 21 , 2024 ; 26662027 (ISSN) ; Hosseinzadeh, K ; Ranjbar Kermani, J ; Ganji, D. D ; Sharif University of Technology
Elsevier
2024
Abstract
Heat exchangers (HE) are one of the vital heat transfer equipment that have various applications in disparate industries. In this regard, countless methods have been implemented to increase and optimize the heat transfer process inside them. However, passive techniques have received more attention due to the absence of external power consumption. In this study, the impact of employing turbulators with various geometries on the overall heat transfer coefficient (HTC), flow pressure drop (PD), and temperature distribution in the shell-and-tube heat exchanger (STHE) has been computationally investigated. Moreover, for a better examination, the effect of variation of the middle diameter of the...
Modified Buongiorno's model for fully developed mixed convection flow of nanofluids in a vertical annular pipe
, Article Computers and Fluids ; Vol. 89 , 2014 , pp. 124-132 ; ISSN: 00457930 ; Moshizi, S. A ; Soltani, E. G ; Ganji, D. D ; Sharif University of Technology
2014
Abstract
This paper deals with the mixed convective heat transfer of nanofluids through a concentric vertical annulus. Because of the non-adherence of the fluid-solid interface in the presence of nanoparticle migrations, known as slip condition, the Navier's slip boundary condition was considered at the pipe walls. The employed model for nanofluid includes the modified two-component four-equation non-homogeneous equilibrium model that fully accounts for the effects of nanoparticles volume fraction distribution. Assuming the fully developed flow and heat transfer, the basic partial differential equations including continuity, momentum, and energy equations have been reduced to two-point ordinary...
Measurement, analysis and reconstruction of residual stresses
, Article Journal of Strain Analysis for Engineering Design ; Volume 47, Issue 4 , February , 2012 , Pages 254-264 ; 03093247 (ISSN) ; Goudar, D ; Farrahi, G. H ; Smith, D. J ; Sharif University of Technology
2012
Abstract
Residual stresses, created in a steel beam by elastic-plastic bending, are predicted using an approximate analysis and the finite element method. The predictions are compared to experimental measurements obtained from the application of incremental centre hole drilling, deep hole drilling and neutron diffraction methods. Finite element simulations of the incremental centre hole drilling and deep hole drilling methods applied to the predicted residual stresses permitted an assessment of their ability to reconstruct the stresses. An analytical reconstruction analysis using an Airy stress function together with boundary and equilibrium conditions is developed and applied to the predictions and...