Search for: moving-boundary
0.015 seconds
Total 21 records

    Diffusional release of a dispersed solute from a cylindrical polymeric matrix into an infinite external volume

    , Article Applied Mathematics and Computation ; Volume 259 , May , 2015 , Pages 676-685 ; 00963003 (ISSN) Khamene, Z. M ; Abdekhodaie, M. J ; Sharif University of Technology
    Elsevier Inc  2015
    Numerical and analytical exact solutions of diffusional release from a cylindrical polymeric matrix into an infinite medium have been developed in which the initial solute loading (A) is greater than solubility limit (Cs). Also, the effects of boundary layers on the drug release rate have been studied. The numerical solution is valid for any initial drug loading whereas analytical solution can be used for high values of drug loading. Comparisons have been made between numerical and analytical exact solutions in upper and lower bounds (A/Cs蠑1 and A/Cs→1) and previously presented approximate solution. The presented results validate the proposed numerical solution  

    Some Innovations in Numerical Simulation of Inviscid Three Dimensional Flow with Moving Boundaries

    , Ph.D. Dissertation Sharif University of Technology Ramezani, Ali (Author) ; Mazaheri, Karim (Supervisor)
    The main subject of this thesis is to improve conventional CFD algorithms applied in numerical simulation of inviscid unsteady flows around moving boundaries with large relative motions, on unstructured grids. All challenges in this regard are reviewed, and appropriate efficient schemes are introduced to address them. A new scheme is presented for valid grid generation during grid movement and is implemented for 2D and 3D problems. Customary three dimensional convergence acceleration techniques such as implicit time stepping and multigriding have been applied. For implicit solution of the flow equations a new algorithm is used. Via a special renumbering algorithm, the approximate... 

    Simulation of Aerosol Transport and Deposition in the Alveolar Zone of the Human Lung

    , M.Sc. Thesis Sharif University of Technology Abdollahpour, Yasser (Author) ; Saiedi, Mohammad Saeid (Supervisor)
    In this study numerical methods are used for modeling flow and simulation of aerosol transport and deposition in alveolar zone of human lung. The flow modeling is done by FLUENT code, using its moving boundaries feature. For particle tracking we developed a code that uses results of velocity field obtained by FLUENT code. Two-dimensional the axisymmetric model was investigated in this study, and was exhibited that rhythmically expanding walls in alveolar duct model has significant influence on flow patterns and particles transport mechanism. In this study we also developed a three-dimensional model of a single alveolated duct with moving boundaries allowing for the cyclic expansion and... 

    A reduced domain strategy for local mesh movement application in unstructured grids

    , Article Applied Numerical Mathematics ; Volume 61, Issue 9 , 2011 , Pages 1001-1016 ; 01689274 (ISSN) Darbandi, M ; Fouladi, N ; Sharif University of Technology
    Automatic control of mesh movement is mandatory in many fluid flow and fluid-solid interaction problems. This paper presents a new strategy, called reduced domain strategy (RDS), which enhances the efficiency of node connectivity-based mesh movement methods and moves the unstructured grid locally and effectively. The strategy dramatically reduces the grid computations by dividing the unstructured grid into two active and inactive zones. After any local boundary movement, the grid movement is performed only within the active zone. To enhance the efficiency of our strategy, we also develop an automatic mesh partitioning scheme. This scheme benefits from a new quasi-structured mesh data... 

    A moving-mesh finite-volume method to solve free-surface seepage problem in arbitrary geometries

    , Article International Journal for Numerical and Analytical Methods in Geomechanics ; Volume 31, Issue 14 , 2007 , Pages 1609-1629 ; 03639061 (ISSN) Darbandi, M ; Torabi, S. O ; Saadat, M ; Daghighi, Y ; Jarrahbashi, D ; Sharif University of Technology
    The main objective of this work is to develop a novel moving-mesh finite-volume method capable of solving the seepage problem in domains with arbitrary geometries. One major difficulty in analysing the seepage problem is the position of phreatic boundary which is unknown at the beginning of solution. In the current algorithm, we first choose an arbitrary solution domain with a hypothetical phreatic boundary and distribute the finite volumes therein. Then, we derive the conservative statement on a curvilinear co-ordinate system for each cell and implement the known boundary conditions all over the solution domain. Defining a consistency factor, the inconsistency between the hypothesis... 

    Comparison of boundary slip for two variants of immersed boundary method in lattice Boltzmann framework

    , Article Physica A: Statistical Mechanics and its Applications ; Vol. 404 , 2014 , Pages 200-216 ; ISSN: 03784371 Farnoush, S ; Manzari, M. T ; Sharif University of Technology
    In this paper, the Immersed Moving Boundary-Lattice Boltzmann (IMB-LB) method is compared with the single relaxation time and multiple-relaxation-time versions of the Immersed Boundary-Lattice Boltzmann (IB-LB) method in terms of the amount of numerical velocity slip produced on solid boundaries. The comparisons are performed for both straight and curved boundaries based on the effects of thickness of virtual domain used in the IB method for the first time, and relaxation time parameter(s) of the LB method. For the straight boundaries, a shear flow problem is studied while for the curved boundaries, a falling circular cylinder in an infinite channel is investigated. First, sensitivities of... 

    Developing a unified FVE-ALE approach to solve unsteady fluid flow with moving boundaries

    , Article International Journal for Numerical Methods in Fluids ; Volume 63, Issue 1 , 2010 , Pages 40-68 ; 02712091 (ISSN) Naderi, A ; Darbandi, M ; Taeibi Rahni, M ; Sharif University of Technology
    In this study, an arbitrary Lagrangian-Eulerian (ALE) approach is incorporated with a mixed finite-volume-element (FVE) method to establish a novel moving boundary method for simulating unsteady incompressible flow on non-stationary meshes. The method collects the advantages of both finite-volume and finite-element (FE) methods as well as the ALE approach in a unified algorithm. In this regard, the convection terms are treated at the cell faces using a physical-influence upwinding scheme, while the diffusion terms are treated using bilinear FE shape functions. On the other hand, the performance of ALE approach is improved by using the Laplace method to improve the hybrid grids, involving... 

    Prediciton of Suspensions Bulk Viscosity Using Immersed Boundary Approach in the Framework of the Lattice Boltzmann Method

    , Ph.D. Dissertation Sharif University of Technology Farnoush, Somayeh (Author) ; Taghizadeh Manzari, Mehrdad (Supervisor)
    In this study, bulk viscosity of suspensions is predicted using numerical simulation.The elaborated numerical method consists of the lattice Boltzmann (LB) method for fluid matrix simulation and the immersed boundary (IB) method for solid boundary implementation. In order to successfully implement the IB method in the frame-work of the LB method, two important challenges, which are body force modeling in the LB method and numerical velocity slip on solid boundaries, are discussed. As a first challenge, body force modeling in the LB method is studied by using a uni-fied framework which has been devised in this study. Using this unified framework,firstly, errors of different body force... 

    A Unified Fve-Ale Approach to Solve Unsteady Laminar to Turbulent Flow on Moving Boundary Domains

    , Ph.D. Dissertation Sharif University of Technology Naderi, Alireza (Author) ; Darbandi, Masoud (Supervisor) ; Taeibi Rahni, Mohammad (Supervisor)
    In this study, an arbitrary Lagrangian-Eulerian (ALE) approach is incorporated with a mixed finite- volume-element (FVE) method to establish a novel moving boundary algorithm to simulate unsteady incompressible flow on non-stationary meshes. The method collects the advantages of both finite-volume and finite-element methods as well as the ALE approach in a unified algorithm capable of solving laminar, transient, and turbulent flows in fluid flow problems with moving boundaries. To enhance the robustness of the extended algorithm, we treat the convection terms at the cell faces using a physical influence upwinding scheme, while the diffusion terms are treated using bilinear finite-element... 

    Simulation of Self-Propulsive Phenomenon, Using Lattice Boltzmann Method

    , M.Sc. Thesis Sharif University of Technology Beigzadeh Abbassi, Mohammad Reza (Author) ; Tayyebi Rahni, Mohammad (Supervisor) ; Taghizadeh Manzari, Mehrdad (Supervisor)
    Many human inventions are inspired by nature, such as fish swimming, bird/insect flight, etc. A basic consideration for the design of swimming machines is the design of propulsors. A creative design of propulsors can be inspired by fish locomotion. The term locomotion means that thrust is generated by undulation of fish body. Thus, there is no need to have an external propulsor. We need to understand how thrust is obtained by fish locomotion. In this study, sub-carangiform motion, which is a well known locomotion and which is practiced by most fish, is simulated numerically using Lattice Boltzmann method (LBM). To simulate the geometry of fishlike body, the profile of a flexible airfoil... 

    A Multiscale Moving Boundary Model For Cancer Invasion

    , M.Sc. Thesis Sharif University of Technology Mohammad Mirzaei, Navid (Author) ; Fotouhi Firoozabad, Morteza (Supervisor)
    Cancer invasion of tissue is a key aspect of the growth and spread of cancer and is crucial in the process of metastatic spread i.e. the growth of secondary cancers. Invasion consists in cancer cells secreting various matrix degrading enzymes (MDEs) which destroy the surronding tissue or extracellular matrix (ECM). Through a combination of proliferation and migration, the cancer cells then actively spread locally into the surrounding tissue. Thus processes occuring at the level of individual cells eventually give rise to processes occuring at the tissue level. In this thesis we introduce a new type of multiscale model describing the process of cancer invasion of tissue.Our multiscale model... 

    Modeling and Experimental Study of Gas Reservoir Formation Damage Caused by Solid-based Drilling Fluids

    , M.Sc. Thesis Sharif University of Technology Vasheghani Farahani, Mehrdad (Author) ; Jamshidi, Saeed (Supervisor)
    Nowadays, one of the most challenges in drilling and production engineering, is the formation damage caused by fluid filtration while drilling and completion operations. This damage would cause serious problems in pay zone and besides influencing the well performance during its life time – due to permeability reduction in near wellbore area- and cause economic expenses such as workover and stimulation operation. Therefore, considering the aspects of formation damage minimization during drilling and completion operations, the fluid selection for these purposes would be crucial. It requires the knowledge of interactions between these fluids and the reservoir rock. In this thesis, using the... 

    Experimental Study for Determining the Diffusion Coefficient of Nitrogen and Methane Gases in Crude Oil

    , M.Sc. Thesis Sharif University of Technology Ghorbani, Mohammad (Author) ; Ghazanfari, Mohammad Hossein (Supervisor)
    Gas injection is one of the common methods for enhance oil recovery from oil reservoirs. At miscible injection condition, the efficiency of the process is majorly affected by the molecular diffusion coefficient of the gas in the oil. Therefore, the accurate value of this coefficient is an essential for applying in reservoir simulator. However, determination of this coefficient only is possible through experimental methods. In this study, pressure decay method was applied to determine the diffusion coefficient of nitrogen, methane and carbon dioxide gases in crude oil. The reasons for choosing this method are : accuracy in designing the experiment, covering a wide range of pressure... 

    A new semi-analytical modeling of steam-assisted gravity drainage in heavy oil reservoirs

    , Article Journal of Petroleum Science and Engineering ; Volume 69, Issue 3-4 , 2009 , Pages 261-270 ; 09204105 (ISSN) Alali, N ; Pishvaie, M. R ; Jabbari, H ; Sharif University of Technology
    Thermal recovery by steam injection has proven to be an effective means of recovering heavy oil. Forecasts of reservoir response to the application of steam are necessary before starting a steam drive project. Thermal numerical models are available to provide forecasts. However, these models are expensive and consume a great deal of computer time. An alternative to numerical modeling is to use a semi-analytical model. The objective of the current study was to investigate thermal applications of horizontal wells for displacement and gravity drainage processes using analytical modeling as well as reservoir simulation. The main novelties presented in the paper are: a) the transient temperature... 

    Molecular Diffusion in the Dynamics Brain Extracellular Space

    , Ph.D. Dissertation Sharif University of Technology Yousefnezhad, Mohsen (Author) ; Fotouhi, Morteza (Supervisor) ; Kamali Zare, Padideh (Co-Advisor) ; Vejdani, Kaveh (Co-Advisor)
    In the thesis , we present a universal model of brain tissue microstructure that dynamically links osmosis and diffusion with geometrical parameters of brain extracellular space (ECS) . In the first part , we investigate the biological aspects of the model , and in the second , we analysis the model in the mathematical framework . The first part : Our model robustly describes and predicts the nonlinear time dependency of tortuosity ($\lambda = \sqrt{D/{D^{*}}}$) changes with very high precision in various media with uniform and nonuniform osmolarity distribution , as demonstrated by previously published experimental data ($D$ = free diffusion coefficient , $D^{*}$ = effective... 

    An Implicit Algorithm for Numerical Simulation of Large Deformation Structures with Incompressible Fluid Flow

    , Ph.D. Dissertation Sharif University of Technology Fouladi, Nematollah (Author) ; Darbandi, Masoud (Supervisor)
    The fluid structure interaction (FSI) problems are widely encountered in many industrial applications in mechanical, aerospace, biomedical, marine, and wind engineering. The main contributions of this research are focused on simulating flow with moving or deforming boundaries including FSI problems with large movement or deformations. In this regard, a hybrid finite-element-volume (FEV) method was used in an arbitrary Lagrangian-Eulerian (ALE) framework. In this research, a new layer-by-layer mesh movement strategy was developed to perform the unstructured grid movement more robustly. This strategy converts the complex data structure of an unstructured grid to a simple quasi-structured data... 

    Dynamic Simulation of Wettability Alteration Induced by Low-Salinity-Effect: Study of Phenomena within Thin Water Film

    , M.Sc. Thesis Sharif University of Technology Pourakaberian, Arash (Author) ; Mahani, Hassan (Supervisor) ; Joekar Niasar, Vahid (Co-Supervisor)
    Recent experimental studies have demonstrated that the lowering of brine could alter the wettability of the oil-brine-rock systems from an oil-wetting state toward a more water-wetting state. This so-called “Low-salinity effect” (LSE) is one of the main effects of the enhanced oil recovery technology based on low-salinity waterflooding. “Double layer expansion” (DLE) in the thin brine film is proposed as the principal mechanism of this phenomenon. Nonetheless, the role of the electrical behavior of the oil/brine and rock/brine interfaces on the kinetics and dynamics of this process is not well understood. Moreover, since most of the previous works have either dealt with a thin film at... 

    A theoretical multi-reflection method for analysis of optomechanical behavior of the Fabry-Perot cavity with moving boundary condition

    , Article Optics Communications ; Volume 284, Issue 19 , 2011 , Pages 4789-4794 ; 00304018 (ISSN) Bahrampour, A. R ; Vahedi, M ; Abdi, M ; Ghobadi, R ; Golshani, M ; Tofighi, S ; Parvin, B ; Sharif University of Technology
    The opto-mechanical coupling and the generation of Stokes and anti-Stokes frequencies in the in-band and intra-band regimes of operation of the Fabry-Perot cavity with a moving mirror on the basis of multi-reflection method (MRM) are described by a unique theory. The frequency characteristic function of the Fabry-Perot filter is modified. By increasing the amplitude of mirror oscillation the Fabry-Perot bandwidth increases and normal mode splitting occurred. The conversion efficiencies of the Stokes and anti-Stokes frequencies versus the mechanical amplitude of oscillation have an optimum value. Also, the delay function corresponding to the radiation pressure is obtained  

    Static recrystallization behavior of AEREX350 superalloy

    , Article Materials Science and Engineering A ; Volume 527, Issue 27-28 , October , 2010 , Pages 7313-7317 ; 09215093 (ISSN) Hosseinifar, M ; Asgari, S ; Sharif University of Technology
    The recrystallization behavior of a commercial nickel-cobalt base superalloy, AEREX 350, is investigated by means of hardness test, X-ray diffraction, and microscopy. It is found that the alloy resists recrystallization up to a high temperature of 1025 °C. Recrystallized grains are readily formed at grain boundaries below this temperature; however, the growth of these new grains is inhibited by Widmanstätten η particles having coherent facets with the nickel matrix (γ). The passage of the recrystallization front results in coherency loss and consequently dissolution of the η platelets. Recrystallization proceeds with a discontinuous precipitation of the η phase behind the moving boundary  

    Improvement of polymer flooding using in-situ releasing of smart nano-scale coated polymer particles in porous media

    , Article Energy Exploration and Exploitation ; Volume 30, Issue 6 , 2012 , Pages 915-940 ; 01445987 (ISSN) Ashrafizadeh, M ; Ramazani, S. A. A ; Sadeghnejad, S ; Sharif University of Technology
    The main purpose of this paper is modeling and simulation of in-situ releasing of smart nano-sized core-shell particles at the water-oil interface during polymer flooding. During the polymer flooding process, when these nano-particles reach the water-oil interface, migrate to the oil phase and the hydrophobic layer of them dissolves in this phase. After dissolution of this protective nano-sized layer, the hydrophilic core containing a water-soluble ultra high molecular weight polymer diffuses back into the water phase and with dissolving in this phase, dramatically increases viscosity of flooding water in the neighborhood of the water-oil interface. In this study, two different...