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Experimental Investigation and Design of an Optimum Fouling Removal Method for a Hull Cleaning Robot
, M.Sc. Thesis Sharif University of Technology ; Khorasanchi, Mahdi (Supervisor) ; Durali, Mohammad (Co-Supervisor)
Abstract
The repair, maintenance and cleaning of marine equipment and ships, as well as the optimization of these operations to reduce their costs have always been of interest to researchers. After a few hours of floating in seawater, an inanimate organic layer forms on the surface of marine structures. After a few months, the thickness of this layer increases. This will increase the drag by 30 to 40 percent. Hull cleaning operation increases efficiency, saves time and money, prolongs equipment life and reduces maintenance and repair costs.In this project, the types of marine fouling according to environmental conditions were identified, next a type of fouling (Barnacle) was selected, which has more...
Simulation and Optimization of Relatively New Catalyst Recovery from Old Catalysts Used in the FCC Process by Applying Electrostatic Field
, M.Sc. Thesis Sharif University of Technology ; Rashtchian, Davood (Supervisor) ; Fotovat, Farzam (Supervisor)
Abstract
In this thesis, the separation process for used and relatively new catalysts of residue fluid catalytic cracking unit by applying an electric field was evaluated. The main purpose of this dissertation is to simulate and design a separation system for separating used and relatively new catalysts of the FCC process in the electrostatic fields. In this regard, various separators were studied, and most of them were simulated under different circumstances. Finally, after examining and analyzing the particle behavior in each of the scenarios, the proposed system was introduced as more effective and efficient than the other separators in order to achieve the ideal separation of the used and...
Determination of the Minimum Fluidization Velocity of an Object Immersed in a Bubbling Fluidized Bed through the CFD-DEM Simulations
, M.Sc. Thesis Sharif University of Technology ; Fotovat, Farzam (Supervisor)
Abstract
Due to the unique advantages of fluidized beds for solid mixing and heat transfer, they are widely used for the thermal processing of solid fuel particles. In practice, such systems are composed of non-conventional fuel particles such as coal or biomass, which are completely different in shape, size, and density from the bed material such as sand. In such systems, correct understanding of the main fluidization parameters such as the minimum fluidization velocity (Umf) of the bed components plays a key role in the successful design and control of the system. However, the onset of fluidization of irregular particles is not clear as it may vary depending on the physical properties of the...
CFD-DEM approach to investigate the effect of drill pipe rotation on cuttings transport behavior
, Article Journal of Petroleum Science and Engineering ; Volume 127 , 2015 , Pages 229-244 ; 09204105 (ISSN) ; Behzad, M ; Rajabi, M ; Sharif University of Technology
Abstract
Increasing cuttings bed height is a serious concern during extended-reach well drilling. In order to predict and prevent cuttings bed height increase, it is essential to study how the critical parameters influence the cuttings transport, especially the drill pipe rotation effects on the cuttings transport process. In conventional models for cuttings transport, the dynamic behavior of particles due to drill pipe rotation is neglected or empirically simplified. This paper presents a coupled Computational Fluid Dynamics and Discrete Element Method (CFD-DEM) approach to simulate the cuttings transport considering the dynamic collision process. The fluid phase is treated as an Eulerian continuum...
Prediction of equilibrium mixing state in binary particle spouted beds: Effects of solids density and diameter differences, gas velocity, and bed aspect ratio
, Article Advanced Powder Technology ; Volume 26, Issue 5 , 2015 , Pages 1371-1382 ; 09218831 (ISSN) ; Dehkordi, A. M ; Sharif University of Technology
Elsevier
2015
Abstract
The state of solids mixing can be considered as a key factor in accomplishment of high efficiency and a uniform product in gas-solid fluidized-beds operating with several different particle sizes. In the present work, coupled DEM-CFD approach was used to carefully investigate the mixing process of binary particles in flat-bottom spouted beds. In this regard, simultaneous effects of particle specifications, operating conditions, and bed dimensions on the equilibrium mixing state of solid mixture were evaluated in detail. Moreover, taking into account the contribution of various parameters, the obtained simulation results were used to draw a correlation for predicting the equilibrium mixing...
On the particle–particle contact effects on the hole cleaning process via a CFD–DEM model
, Article Particulate Science and Technology ; 2016 , Pages 1-8 ; 02726351 (ISSN) ; Behzad, M ; Rajabi, M ; Sharif University of Technology
Taylor and Francis Inc
Abstract
The accurate and precise computational models in order to predict the hole cleaning process is one of the helpful assets in drilling industries. Besides the bulk properties such as the flow velocity, particles average size, cleaning fluid properties, etc., that will affect the cleaning process, there is an unanswered question about the microscopic properties of the particles, particularly those which determines the contact characteristics: Do those play a major role or not? The rudimentary answer is not. The first purpose of the present work is to answer this question via a developed computational fluid dynamics coupled with discrete element method (CFD–DEM) in which the six unknown rolling...
CFD-DEM simulation of the hole cleaning process in a deviated well drilling: the effects of particle shape
, Article Particuology ; Volume 25 , 2016 , Pages 72-82 ; 16742001 (ISSN) ; Behzad, M ; Rajabi, M ; Sharif University of Technology
Abstract
We investigate the effect of particle shape on the transportation mechanism in well-drilling using a three-dimensional model that couples computational fluid dynamics (CFD) with the discrete element method (DEM). This numerical method allows us to incorporate the fluid-particle interactions (drag force, contact force, Saffman lift force, Magnus lift force, buoyancy force) using momentum exchange and the non-Newtonian behavior of the fluid. The interactions of particle-particle, particle-wall, and particle-drill pipe are taken into account with the Hertz-Mindlin model. We compare the transport of spheres with non-spherical particles (non-smooth sphere, disc, and cubic) constructed via the...
Simulation of the interaction between nonspherical particles within the CFD–DEM framework via multisphere approximation and rolling resistance method
, Article Particulate Science and Technology ; 2015 , Pages 1-11 ; 02726351 (ISSN) ; Behzad, M ; Rajabi, M ; Sharif University of Technology
Taylor and Francis Inc
2015
Abstract
The particle shape is an important factor playing critical role in evaluation of the interactions between particles in high-concentration particle-fluid flows. In this paper, the well-known multisphere (MS) approximation approach and the novel rolling resistance approach are utilized to examine their performance in order to simplify the generalized shaped particle’s interactions within the framework of discrete element method (DEM) and computational fluid dynamics (CFD). The performance of two approaches are compared with the perfect particle’s shape geometry, for the limited cases of cubic-shaped and disk-shaped particle flows in a horizontal well drilling process as a reference scenario....
Simulation of the interaction between nonspherical particles within the CFD–DEM framework via multisphere approximation and rolling resistance method
, Article Particulate Science and Technology ; Volume 34, Issue 4 , 2016 , Pages 381-391 ; 02726351 (ISSN) ; Behzad, M ; Rajabi, M ; Sharif University of Technology
Taylor and Francis Inc
Abstract
The particle shape is an important factor playing critical role in evaluation of the interactions between particles in high-concentration particle-fluid flows. In this paper, the well-known multisphere (MS) approximation approach and the novel rolling resistance approach are utilized to examine their performance in order to simplify the generalized shaped particle’s interactions within the framework of discrete element method (DEM) and computational fluid dynamics (CFD). The performance of two approaches are compared with the perfect particle’s shape geometry, for the limited cases of cubic-shaped and disk-shaped particle flows in a horizontal well drilling process as a reference scenario....
CFD-DEM modeling of cuttings transport in underbalanced drilling considering aerated mud effects and downhole conditions
, Article Journal of Petroleum Science and Engineering ; Volume 160 , 2018 , Pages 229-246 ; 09204105 (ISSN) ; Rajabi, M ; Sharif University of Technology
Elsevier B.V
2018
Abstract
This paper presents a developed CFD (Computational fluid dynamics)-DEM (Discrete elements method) model to study the cuttings transportation in aerated mud drilling process for inclined annuli at downhole conditions. The model is conducted to determine the effects of liquid flow rate, air injection rate, annulus inclination angle, elevated temperature and pressure on the cuttings transport efficiency. The motion of the fluid is computed using CFD based approach with gas–liquid interface capturing provided by the volume-of-fluid (VOF) method. The dynamics of cutting phase is studied by DEM using soft sphere approach in order to take into account the particle collision phenomenon. The...
Simulation of proppant transport at intersection of hydraulic fracture and natural fracture of wellbores using CFD-DEM
, Article Particuology ; Volume 63 , 2022 , Pages 112-124 ; 16742001 (ISSN) ; Rajabi, M ; Sharif University of Technology
Elsevier B.V
2022
Abstract
Proppants transport is an advanced technique to improve the hydraulic fracture phenomenon, in order to promote the versatility of gas/oil reservoirs. A numerical simulation of proppants transport at both hydraulic fracture (HF) and natural fracture (NF) intersection is performed to provide a better understanding of key factors which cause, or contribute to proppants transport in HF–NF intersection. Computational fluid dynamics (CFD) in association with discrete element method (DEM) is used to model the complex interactions between proppant particles, host fluid medium and fractured walls. The effect of non-spherical geometry of particles is considered in this model, using the multi-sphere...
Computer simulation of the effect of particle stiffness coefficient on the particle-fluid flows
, Article Particulate Science and Technology ; Volume 40, Issue 2 , 2022 , Pages 233-242 ; 02726351 (ISSN) ; Rajabi, M ; Sharif University of Technology
Taylor and Francis Ltd
2022
Abstract
The Computational fluid dynamics (CFD)–discrete element method (DEM) numerical simulation may be applied to predict the hydrodynamic behavior of dense particle–fluid flows. The main drawback of this simulation is the long computational time required owing to the large number of particles and the minute time-step required to maintain a stable solution. In this work, a new method to improve the efficiency and accuracy of CFD–DEM simulations is presented. The particle stiffness coefficient is used as a flexible parameter to improve the accuracy and efficiency of the model. The particle concentration distribution results are compared with experimental one’s to derive the optimum effective...
CFD-DEM Model for Simulation of Non-spherical Particles in Hole Cleaning Process
, Article Particulate Science and Technology ; Volume 33, Issue 5 , 2015 , Pages 472-481 ; 02726351 (ISSN) ; Behzad, M ; Rajabi, M ; Sharif University of Technology
Taylor and Francis Inc
2015
Abstract
During the well drilling process, particles are produced in different shapes. The shape of particles can influence the characteristics of particles transport process. The aim of this work is to analyze the effects of particle shape on the transportation mechanism. For this purpose, a three-dimensional model is prepared for simulation of particle transportation with spherical and non-spherical shapes, during deviated well drilling. The motion of particles and the non-Newtonian fluid flow are simulated via discrete element method and CFD, respectively. The two-way coupling scheme is used to incorporate the effects of fluid-particle interactions. Three different samples of non-spherical shapes...