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    Linearized and non-linear acoustic/viscous splitting techniques for low Mach number flows

    , Article International Journal for Numerical Methods in Fluids ; Volume 42, Issue 10 , 2003 , Pages 1059-1072 ; 02712091 (ISSN) Farshchi, M ; Hannani, S. K ; Ebrahimi, M ; Sharif University of Technology
    2003
    Abstract
    Computation of the acoustic disturbances generated by unsteady low-speed flow fields including vortices and shear layers is considered. The equations governing the generation and propagation of acoustic fluctuations are derived from a two-step acoustic/viscous splitting technique. An optimized high order dispersion-relation-preserving scheme is used for the solution of the acoustic field. The acoustic field generated by a corotating vortex pair is obtained using the above technique. The computed sound field is compared with the existing analytic solution. Results are in good agreement with the analytic solution except near the centre of the vortices where the acoustic pressure becomes... 

    Numerical and experimental investigation of the grain refinement of liquid metals through cavitation processing

    , Article Metals and Materials International ; Volume 19, Issue 5 , September , 2013 , Pages 959-967 ; 15989623 (ISSN) Haghayeghi, R ; Ezzatneshan, E ; Bahai, H ; Nastac, L ; Sharif University of Technology
    2013
    Abstract
    An investigation was carried out on the grain refinement of molten AA5754 Aluminum alloy through intensive shearing. The results show intensive shearing via cavitation decreases the grain size significantly. The above hypothesis for structure refinement was evaluated and an experiment was performed to ensure the creditability of this assumption. Finally, it was simulated by computational fluid dynamics (CFD) modeling. It was understood that shearing is the responsible mechanism for creation of cavitation bubbles and further collapse of them. It was also concluded the pressure which generated from the collapse of the bubble is well enough for braking the oxide layer and wetting them. It was... 

    Numerical investigation of the velocity field and separation efficiency of deoiling hydrocyclones

    , Article Petroleum Science ; Volume 9, Issue 4 , 2012 , Pages 511-520 ; 16725107 (ISSN) Maddahian, R ; Asadi, M ; Farhanieh, B ; Sharif University of Technology
    2012
    Abstract
    Three-dimensional simulation of a multiphase flow is performed using the Eulerian-Eulerian finite volume method in order to evaluate the separation efficiency and velocity field of deoiling hydrocyclones. The solution is developed using a mass conservation-based algorithm (MCBA) with collocated grid arrangement. The mixture approach of the Reynolds stress model is also employed in order to capture features of turbulent multiphase swirling flow. The velocity field and separation efficiency of two different configurations of deoiling hydrocyclones are compared with available experimental data. The comparison shows that the separation efficiency can be predicted with high accuracy using... 

    Modified MODFLOW-based model for simulating the agglomeration and transport of polymer-modified Fe0 nanoparticles in saturated porous media

    , Article Environmental Science and Pollution Research ; 2015 ; 09441344 (ISSN) Babakhani, P ; Fagerlund, F ; Shamsai, A ; Lowry, G. V ; Phenrat, T ; Sharif University of Technology
    Springer Verlag  2015
    Abstract
    The solute transport model MODFLOW has become a standard tool in risk assessment and remediation design. However, particle transport models that take into account both particle agglomeration and deposition phenomena are far less developed. The main objective of the present study was to evaluate the feasibility of adapting the standard code MODFLOW/MT3D to simulate the agglomeration and transport of three different types of polymer-modified nanoscale zerovalent iron (NZVI) in one-dimensional (1-D) and two-dimensional (2-D) saturated porous media. A first-order decay of the particle population was used to account for the agglomeration of particles. An iterative technique was used to optimize... 

    Numerical simulation of base-isolated systems sliding on concave surfaces

    , Article Asian Journal of Civil Engineering ; Volume 11, Issue 1 , 2010 , Pages 123-133 ; 15630854 (ISSN) Jamali, N ; Jamali, S ; Sharif University of Technology
    2010
    Abstract
    Base isolation is an acknowledged means to reduce the transmission of earthquake accelerations from the ground into the structure. Of particular interest here are systems where the bearing slides on a concave surface which produces a self-centering force restoring the building to its original position. While the idea behind the technology is straightforward, the numerical simulation of the structural response is difficult, since the contact between the bearing and the sliding surface changes continually between sticking and sliding in a nonlinear process. The research presented here aims at developing a computational model for base-isolated building which would allow the engineer to simulate... 

    Mitigation of ammonia dispersion with mesh barrier under various atmospheric stability conditions

    , Article Asian Journal of Atmospheric Environment ; Volume 10, Issue 3 , 2016 , Pages 125-136 ; 19766912 (ISSN) Barzegar Gerdroodbary, M ; Mokhtari, M ; Bishehsari, S ; Fallah, K ; Sharif University of Technology
    Korean Society for Atmospheric Environment  2016
    Abstract
    In this study, the effects of the mesh barrier on the free dispersion of ammonia were numerically investigated under different atmospheric conditions. This study presents the detail and flow feature of the dispersion of ammonia through the mesh barrier on various free stream conditions to decline and limit the toxic danger of the ammonia. It is assumed that the dispersion of the ammonia occurred through the leakage in the pipeline. Parametric studies were conducted on the performance of the mesh barrier by using the Reynolds-averaged Navier-Stokes equations with realizable κ-ε turbulence model. Numerical simulations of ammonia dispersion in the presence of mesh barrier revealed significant... 

    Numerical investigation of distance effect between two searasers for hydrodynamic performance

    , Article Alexandria Engineering Journal ; Volume 55, Issue 3 , 2016 , Pages 2257-2268 ; 11100168 (ISSN) Babajani, A. A ; Jafari, M ; Hafezi Sefat, P ; Sharif University of Technology
    Elsevier B.V  2016
    Abstract
    Nowadays, researchers are interested in investigation of the ocean wave energy conversion (OWEC) because this device can convert wave energy into electricity economically. The aim of this study was to evaluate a novel ocean wave energy converter named Searaser which may be capable of being used in the Caspian Sea. One of the ways for improving the efficiency of Searasers is to use numerous Searasers simultaneously. Increasing the number of Searasers not only increases the electricity production but also can help producing more stable electricity. In this article the function of two Searasers three different distances (10, 15 and 20 m) was evaluated numerically by solving momentum and... 

    Numerical investigation of geometric parameter effects on the aerodynamic performance of a Bladeless fan

    , Article Alexandria Engineering Journal ; Volume 55, Issue 1 , 2016 , Pages 223-233 ; 11100168 (ISSN) Jafari, M ; Afshin, H ; Farhanieh, B ; Sojoudi, A ; Sharif University of Technology
    Elsevier  2016
    Abstract
    Aerodynamic performance of a Bladeless fan is numerically investigated considering the effect of five geometric parameters. Airflow through this fan was analyzed by simulating a Bladeless fan within a 2 m × 2 m × 4 m room. Analysis of the flow field inside the fan and the evaluation of its performance were obtained by solving conservations of mass and momentum equations for the aerodynamic investigations. In order to design the Bladeless fan an Eppler 473 airfoil profile was used as the cross section of the fan. Five distinct parameters, namely height of cross section of the fan, outlet angle of the flow relative to the fan axis, thickness of airflow outlet slit, hydraulic diameter, and... 

    Modified MODFLOW-based model for simulating the agglomeration and transport of polymer-modified Fe0 nanoparticles in saturated porous media

    , Article Environmental Science and Pollution Research ; Volume 25, Issue 8 , 2018 , Pages 7180-7199 ; 09441344 (ISSN) Babakhani, P ; Fagerlund, F ; Shamsai, A ; Lowry, G. V ; Phenrat, T ; Sharif University of Technology
    Springer Verlag  2018
    Abstract
    The solute transport model MODFLOW has become a standard tool in risk assessment and remediation design. However, particle transport models that take into account both particle agglomeration and deposition phenomena are far less developed. The main objective of the present study was to evaluate the feasibility of adapting the standard code MODFLOW/MT3D to simulate the agglomeration and transport of three different types of polymer-modified nanoscale zerovalent iron (NZVI) in one-dimensional (1-D) and two-dimensional (2-D) saturated porous media. A first-order decay of the particle population was used to account for the agglomeration of particles. An iterative technique was used to optimize... 

    Drag force on a flat plate in cavitating flows

    , Article Polish Maritime Research ; Volume 16, Issue 3 , 2009 , Pages 18-25 ; 12332585 (ISSN) Seif, M ; Asnaghi, A ; Jahanbakhsh, E ; Sharif University of Technology
    2009
    Abstract
    The present study focuses on the simulation of two dimensional unsteady cavitating flows. For simulation of unsteady behaviors of cavitation which have practical applications, the development of unsteady PISO algorithm based on the non-conservative approach is utilized. For multi-phase simulation, single-fluid Navier-Stokes equations, along with the volume fraction transport equation, are employed. The bubble dynamics model is utilized to simulate phase change between vapor and liquid phases of the water. Unsteady simulation of cavitation around NACA66(MOD) and supercavitation around a flat plate normal to flow direction are performed to clarify accuracy of presented model. Numerical results... 

    Numerical and experimental analysis of copper electroforming on an aluminum substrate as a rotating cone electrode cell

    , Article ChemistrySelect ; Volume 4, Issue 40 , 2019 , Pages 11839-11847 ; 23656549 (ISSN) Memannavaz, H ; Pebdeni, H. H ; Liaghat, G ; Rahmati, S ; Najafi, M ; Fazeli, H ; Sharif University of Technology
    Wiley-Blackwell  2019
    Abstract
    In this paper, the advantages of numerical simulation to improve the process of copper electroforming are demonstrated. In this regard, the finite element model of copper electroforming for a rotating cone electrode was first prepared and then, the effect of the key parameters, such as applied current density, solution conductivity, electrode spacing, and anode height, on the uniformity of the thickness was investigated. The model combines tertiary current distribution with Bulter–Volmer electrode kinetics and computational fluid dynamics at the turbulent condition. In order to validate the model, a cone-shaped shell was produced by electroforming method in the laboratory. The obtained... 

    Experimental and mathematical analysis of electroformed rotating cone electrode

    , Article Korean Journal of Chemical Engineering ; Volume 37, Issue 4 , April , 2020 , Pages 724-729 ; eISSN: 1975-7220 Heydari, H ; Ahmadipouya, S ; Shoaee Maddah, A ; Rokhforouz, M. R ; Sharif University of Technology
    Springer  2020
    Abstract
    In this study, we present results of a mathematical model in which the governing equations of electroforming process were solved using a robust finite element solver (COMSOL Multiphysics). The effects of different parameters including applied current density, solution electrical conductivity, electrode spacing, and anode height on the copper electroforming process have been investigated. An electroforming experiment using copper electroforming cell was conducted to verify the developed model. The obtained results show that by increasing the applied current density, the electroforming process takes place faster, thereby resulting in a higher thickness of the electroformed layer. In addition,... 

    Investigation of Two-Fluid Flow Contains Oil and Water in Hydrocyclones

    , Ph.D. Dissertation Sharif University of Technology Maddahian, Reza (Author) ; Farhanieh, Bijan (Supervisor) ; Firoozabadi, Bahar (Co-Advisor)
    Abstract
    Having an efficient and reliable system for oil-water separation especially in offshore oil and gas industry is of crucial importance. Due to the platform movement, space, weight and operating limitations in offshore industries, using common methods, (e.g. gravity based vessels), for oil-water separation is ineffective. On the other hand, producing oil on offshore platforms is often accompanied by large discharge of oil-contaminated water into the sea, resulting in environmental pollution. Therefore a need for high efficiency compact separators capable of operation in various operating conditions arises. One solution to the mentioned problem is the use of hydrocyclone separators. The... 

    Sedimentation Investigation and Numerical Analysis of Dredging Trailing Disposal

    , M.Sc. Thesis Sharif University of Technology Shahvelayati, Roozbeh (Author) ; Abbaspour Tehrani Fard, Madjid (Supervisor) ; Khorasanchi, Mahdi (Supervisor)
    Abstract
    every year large amounts of sedimentation are getting dredged all over the world. Dredging operation includes several processes such as excavating from the sea bottom, transferring them to the surface, and most important, releasing them in another area which can cause a sediment particle cloud that can be really harmful to the surrounding environment. Therefore, accurate analysis of this phenomenon is necessary to prevent catastrophic damages. The Eulerian-Lagrangian numerical method considers both sediment particles and fluid physics for a better simulation of near-field area. In this project, after investigating open-source available software for the Eulerian-Lagrangian simulation, a new... 

    A coupled experimental and numerical simulation of rock slope joints behavior

    , Article Arabian Journal of Geosciences ; 2014 ; ISSN: 18667511 Haeri, H ; Khaloo, A ; Marji, M. F ; Sharif University of Technology
    Abstract
    In this research, a coupled numerical-experimental analysis of crack propagation, crack coalescence, and breaking process of jointed rock slopes is performed by studying the mechanical behavior of pre-cracked brittle substances considering the specially prepared rock-like specimens (rock-like specimens are specially prepared by a proper mixing of Portland Pozzolana Cement (PPC), fine sand, and water in a rock mechanics laboratory) and natural rock slopes, simultaneously. The numerical analyses are accomplished using a numerical code based on the higher-order displacement discontinuity method (HODDM). A cubic displacement discontinuity variation along each boundary element is assumed to... 

    The Effect of the Step Height on Energy Dissipation in Stepped Spillways Using Numerical Simulation

    , Article Arabian Journal for Science and Engineering ; Vol. 39, issue. 4 , 2014 , p. 2587-2594 Attarian, A ; Hosseini, K ; Abdi, H ; Hosseini, M ; Sharif University of Technology
    Abstract
    From 1970s, studies have been conducted on the hydraulic design of stepped spillways and many empirical formulas were developed. Despite the simple geometry of these spillways, their hydraulic behavior is complicated. As a result, for many cases, the physical models are studied to verify the design. Numerical simulation is considered as a tool to reduce the laboratory tests, in order to save time and money. Furthermore, the parameters which are not investigated or measured in physical models could be evaluated. In this paper, the results of numerical simulations are compared with the results of physical models and empirical formulas for the spillway of Renwick dam studied in a 1/8 scale... 

    Numerical simulation of cellular structure of weak detonation and evaluation of linear stability analysis predictions

    , Article Engineering Applications of Computational Fluid Mechanics ; Volume 7, Issue 3 , 2013 , Pages 308-323 ; 19942060 (ISSN) Barkhordari, A ; Farshchi, M ; Sharif University of Technology
    2013
    Abstract
    This paper investigates the development of cellular structures created by the propagation of a detonation wave in a gaseous mixture. Two dimensional reactive Euler equations with an idealized one-step Arrhenius type reaction model are solved using the PPM scheme coupled with the exact Riemann solver. The numerical flow solver simulates the evolution process of regular cellular structures of a weakly unstable detonation wave. The cellular structures are generated by two-dimensional sinusoidal perturbations imposed on a ZND detonation wave. The initial sinusoidal perturbation wavelengths are predicted from linear stability analysis. The objective of these calculations is to examine the... 

    The effect of fractionality nature in differences between computer simulation and experimental results of a chaotic circuit

    , Article Central European Journal of Physics ; Volume 11, Issue 6 , 2013 , Pages 836-844 ; 18951082 (ISSN) Faraji, S ; Tavazoei, M. S ; Sharif University of Technology
    2013
    Abstract
    In practice, some differences are usually observed between computer simulation and experimental results of a chaotic circuit. In this paper, it is tried to obtain computer simulation results having more correlation with those obtained in practice by using more realistic models for chaotic circuits. This goal is achieved by considering the fractionality nature of electrical capacitors in the model of a chaotic circuit  

    Simulation of ventilation effects on indoor radon

    , Article Management of Environmental Quality ; Volume 24, Issue 3 , 2013 , Pages 394-407 ; 14777835 (ISSN) Akbari, K ; Mahmoudi, J ; Ghanbari, M ; Sharif University of Technology
    2013
    Abstract
    Purpose: The purpose of this paper is to describe the use of computational fluid dynamics (CFD) to simulate indoor radon distribution and ventilation effects. This technique was used to predict and visualize radon content and indoor air quality in a one-family detached house in Stockholm. The effects of intake fans, exhaust fans and doors on radon concentration were investigated. Design/methodology/approach: In this study a mechanically balanced ventilation system and a continuous radon monitor (CRM) were used to measure the indoor ventilation rate and radon levels. In a numerical approach, the FLUENT CFD package was used to simulate radon entry into the building and ventilation effects.... 

    Experimental and numerical simulation of the effect of particles on flow structures in secondary sedimentation tanks

    , Article Journal of Applied Fluid Mechanics ; Volume 5, Issue 2 , 2012 , Pages 15-23 ; 17353572 (ISSN) Asgharzadeh, H ; Firoozabadi, B ; Afshin, H ; Sharif University of Technology
    JAFM  2012
    Abstract
    Sedimentation tanks are designed for removal of floating solids in water flowing through the water treatment plants. These tanks are one of the most important parts of water treatment plants and their performance directly affects the functionality of these systems. Flow pattern has an important role in the design and performance improvement of sedimentation tanks. In this work, an experimental study of particle-laden flow in a rectangular sedimentation tank has been performed. Kaolin was used as solid particles in these experiments. Also, a numerical simulation was developed using the finite volume method with a k-e turbulent model. The results of the numerical model agree well with the...