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Total 98 records

    Investigation of hydroelastic effect in analysis of high-speed craft

    , Article Ships and Offshore Structures ; 2014 ; ISSN: 1754212X Zamanirad, S ; Seif, M. S ; Tabeshpur, M. R ; Yaakob, O ; Sharif University of Technology
    Abstract
    Hydroelastic effect in bottom slamming problem of high-speed craft is one of the most challenging issues in structural design. In this paper, numerical method is used to investigate the hydroelastic effect in bottom-water impact analysis of high-speed monohull craft. Slamming with two viewpoints of rigid and elastic structures (hydroelastic effect) is modelled by coupled computational fluid dynamic (CFD) and finite element method (FEM) techniques. The results showed that considering hydroelastic effect, especially in high-impact speed, reduces the structural deformations and stresses compared with quasi-statistic analysis. The effect of different parameters, such as boundary condition, plate... 

    Fluid-structure interaction analysis of airflow in pulmonary alveoli during normal breathing in healthy humans

    , Article Scientia Iranica ; Volume 23, Issue 4 , 2016 , Pages 1826-1836 ; 10263098 (ISSN) Monjezi, M ; Saidi, M. S ; Sharif University of Technology
    Sharif University of Technology 
    Abstract
    In this work, the human lung alveoli are idealized by a three dimensional honeycomb like geometry and a fluid-structure analysis is performed to study the normal breathing mechanics. In contrast to previous works in which the inlet flow rate is predefined, in this model, we have applied a negative pressure on the outside surface of the alveolus which causes air to flow in and out of the alveolus. The integration of the experimental curve of breathing flow rate was used to approximate the shape of the external applied pressure. Our Fluid-Structure Interaction (FSI) model has an advantage over other literature since it addresses both the fluid dynamics and solid mechanics, simultaneously. The... 

    Submicron particle deposition in pulmonary alveoli during cyclic breathing

    , Article Scientia Iranica ; Volume 24, Issue 4 , 2017 , Pages 1975-1984 ; 10263098 (ISSN) Monjezi, M ; Saidi, M. S ; Ahmadi, G ; Sharif University of Technology
    Sharif University of Technology  2017
    Abstract
    The prediction of deposition efficiency of submicron particles in the pulmonary alveoli has received special attention due to its importance for drug delivery systems and for assessing air pollutants health risks. In this work, the pulmonary alveoli of a healthy human are idealized by a three-dimensional honeycomb-like configuration and a fluid-structure interaction analysis is performed. In contrast to previous works in which the inlet flow rate is predefined, in this model, a negative pressure is imposed on the outside surface of the flalveolus which causes air to flow in and out of the alveolus. The resulting flow patterns confirmed that there was no circulation in the terminal alveolus.... 

    Effects of Mechanical Loading Environment on Aneurysm

    , M.Sc. Thesis Sharif University of Technology Abdollahi, Rahim (Author) ; Abedian, Ali (Supervisor)
    Abstract
    Human body is subjected to body accelerations or vibrations in several circumstances. During gravitational changes, the hydrostatic pressure gradient along the body axis changes, and then body fluids are redistributed. Prolonged exposure to high level external acceleration may lead to serious or even fatal situations on account of disturbances in blood flow. Due to physiological importance of body acceleration many theoretical investigations have been carried out for the flow of blood under the influence of body acceleration. In this study, the mechanical loads that pilots experience during flight are considered. The aim of the present study is to investigate the effects of mechanical... 

    Novel 2D algorithm for fluid solid interaction based on the smoothed particle hydrodynamics (SPH) method

    , Article Scientia Iranica ; Volume 18, Issue 3 B , June , 2011 , Pages 358-367 ; 10263098 (ISSN) Lahooti, M ; Pisheva, A ; Saidi, M. S ; Sharif University of Technology
    2011
    Abstract
    In this study, a pure Lagrangian algorithm for numerical simulation of fluid-structure interaction problems is proposed based on the Smoothed Particle Hydrodynamics (SPH) method. A new treatment of boundary conditions at the interfaces is introduced that provides the possibility of simultaneous integration of governing equations for all particles, regardless of its material type. The proposed algorithm is capable of dealing with large deformations of hypo elastic solids. The method is validated by comparison of numerical results with other numerical simulations and also examining the consistent behaviors of the algorithm for different parameters  

    Treatment of the small time instability in the finite element analysis of fluid structure interaction problems

    , Article International Journal for Numerical Methods in Fluids ; Volume 71, Issue 6 , 2013 , Pages 756-771 ; 02712091 (ISSN) Afrasiab, H ; Movahhedy, M. R ; Sharif University of Technology
    2013
    Abstract
    In this paper, the fluid-structure interaction problem in mechanical systems in which a high frequency vibrating solid structure interacts with the surrounding fluid flow is considered. Such a situation normally appears in many microelectromechanical systems like a wide variety of microfluidic devices. A different implementation of the residual-based variational multiscale flow method is employed within the arbitrary Lagrangian-Eulerian formulation. The combination of the variational multiscale method with appropriate stabilization parameters is used to handle the so-called small time step instability in the finite element analysis of the fluid part in the coupled fluid-structure interaction... 

    Developing and Using Reduced Order Models for Combined Internal and External Fluid-Structure Interaction Problems

    , Ph.D. Dissertation Sharif University of Technology Dehghani Firouzabadi, Roohollah (Author) ; Haddadpour, Hassan (Supervisor)
    Abstract
    This thesis deals with developing and applying reduced order modeling techniques for fluid and structure interaction problems. First, the basis and formulations of reduced order modeling technique in the function space are reviewed. Then the governing equations of structural dynamics as well as incompressible flow are reviewed and some simplifications are applied. Based on the modal analysis technique along with the finite element model of the structure and the boundary element model for flow field, some reduced order models are represented. The represented models are developed for liquid sloshing in moving and elastic tanks, fluid structure interaction in flexible shells conveying flow,... 

    Proposing and Numerical Modeling of Novel Surgical Procedures in Order to Increase Pulsatility Style of TCPC Blood Flow, Using FSI Approach

    , M.Sc. Thesis Sharif University of Technology Rajabzadeh Oghaz, Hamidreza (Author) ; Firoozabadi, Bahar (Supervisor) ; Saidi, Mohammad Said (Co-Advisor)
    Abstract
    Single ventricle anomaly is a congenital heart disease which is characterized by anatomical malformations. The main abnormality that a patient faces is desaturated blood flow, which, without any treatment increases the risk of death. The classical treatment is based on a three stage palliative procedure which should begin from the first few days of patient’s life. The final stage is known as Fontan procedure which directly connects inferior vena-cava to pulmonary arteries without going through the ventricle.This connection is known as Total Cavo Pulmonary Connection (TCPC). After surgery, the single ventricle could supply adequate and saturated systemic blood flow for the body, but TCPC... 

    Nonlinear Vibrations of Conical Shells with Concurrent Internal and External Flows

    , Ph.D. Dissertation Sharif University of Technology Rahmanian, Mohammad (Author) ; Dehghani Firouz Abadi, Ruhollah (Supervisor)
    Abstract
    In the current study, nonlinear vibration and stability of conical shells with both separate and concurrent internal and external flows are studied. External and internal flows are in the supersonic and subsonic regimes, respectively. The Krumhar’s aerodynamic piston theory is utilized to model the external loading on the structure as well as the compressible potential flow model to capture the internal fluid dynamics. The so-called compressible fluid model is obtained via simplification of the Navier-Stockes equations after applying the inviscid and irrotational assumptions. The nonlinear structural equations of motion are derived using the Hamiltonian dynamics approach and utilizing the... 

    Influence of Geometrical Parameters on Hemodynamics of Blood Flow in Coronary Artery Bypass Graft by FSI Numerical Method

    , M.Sc. Thesis Sharif University of Technology Saffari, Ali (Author) ; Halali, Mohammad (Supervisor) ; Hossein Ahmadi, Zargham (Supervisor)
    Abstract
    In this study, the simulation of blood flow through a stenosed coronary artery and a bypass graft are discussed using fluid-structure interaction numerical method. Effects of the geometrical parameters of CABG surgery on hemodynamics have been studied. Investigated hemodynamic variables include shear stress on the vessel wall, the velocity profile in high-risk areas and the pathlines. Lower than 0.5 Pa shear stress on intimal layer of arteries causes the formation of plaque on the wall. Angle of 30 degrees and diameter ratio of bypass to host artery of 1:1 are proposed as the optimum geometry. The distance of the anastomosis from the site of occlusion has no effect on surgery. Also,... 

    3-D Seismic Evaluation of on Grade Cylindrical Flexible Storage Tanks Considering Soil-Structure Interaction

    , M.Sc. Thesis Sharif University of Technology Andalib, Reza (Author) ; Rahimzadeh Rofooei, Fayaz (Supervisor)
    Abstract
    The circular flexible cylindrical liquid tanks usually are made of steel or aluminum and in majority of cases are built on grade due to its economic advantages. The most important part of a safe design of a storage tanks is the accurate estimation of the seismically induced lateral forces that should be transferred to its base through the tank shell and its support. Seismic behavior of liquid storage tanks is quite different from regular buildings and industrial structures due to its nonlinear behavior caused by complex distribution of hydrodynamic pressure, buckling of its walls, etc.. Moreover, the effect of rocking motion caused by the under laying soft soil, on its response parameters... 

    Seismic Behavior Evaluation of Anchored Cylindrical Fixed Roof Storage Tanks with Soil-Structure Interaction Effect

    , M.Sc. Thesis Sharif University of Technology Rasoulbeigi Fard, Mohammad Reza (Author) ; Rahimzadeh Rofouei, Fayyaz (Supervisor)
    Abstract
    The importance of the liquid storage tanks in this era is as much as their contained liquid that we use in our daily lives. Many studies have been carried out on these influential structures considering various aspects. The major damages inflicted to the liquid storage tanks in Loma Prieta, Lozan, Hokaido, Arzinkan, Northridge, Kobe, Izmit & Haiti Earthquakes, has led the researchers to perform various experimental and analytical studies on this regard in the last few decades. The most important part of a safe design of a storage tank is the accurate estimation of the seismically induced lateral forces that should be transferred to its base through the tank shell and its support. Moreover,... 

    On The Stability of Spinning Composite Cylindrical Shells Partially Filled With Liquid

    , M.Sc. Thesis Sharif University of Technology Permoon, Mohammad Reza (Author) ; Haddadpour, Hassan (Supervisor) ; Dehghani Firoozabadi, Rohollah (Supervisor)
    Abstract
    In the present project an analytical model is proposed for the instability of spinning composite cylindrical shells partially filled with fluid. For this purpose, using the linearized Navier-Stokes equation for the incompressible flow, a 2-D model is developed for fluid motion at each section of the cylinder. The resultant pressure exerted on the cylinder wall as the result of the fluid motion, are calculated in terms of elastic displacements of the cylinder. Applying the Hamilton principle, the governing equations of motion of the cylinder are derived and then combined with the equations describing the fluid pressure to obtain the coupled-field equations of the structural-fluid motion.... 

    Dynamic Simulation and Hydro-elastic Stability Analysis of Flexible Supercavitating Projectiles

    , Ph.D. Dissertation Sharif University of Technology Ahmadi Tehrani, Majid (Author) ; Dehghani Firouzabadi, Roohallah (Supervisor)
    Abstract
    At high speeds, cavitation bubbles form at the sharp edges of the submerged body or in situations where the pressure falls below the fluid vapor pressure. By placing a suitable cavitator in the nose of the body, the cavitation bubbles are cobined by increasing the speed and the whole body is placed inside the cavity. The formation of a supercavity leads to a significant reduction in the drag force of the vehicle. The submersible device is in contact with the fluid at two points, the cavitator and the fins, and due to the location of the cavitator in the nose of the body, the forces acting on it play an important role in the stability and control of the device.The main goal of current... 

    Computer simulations of sodium formate solution in a mixing tank

    , Article Communications in Nonlinear Science and Numerical Simulation ; Volume 13, Issue 2 , 2008 , Pages 380-399 ; 10075704 (ISSN) Mousavi, S. M ; Zamankhan, P ; Jafari, A ; Sharif University of Technology
    2008
    Abstract
    Traditionally, solid-liquid mixing has always been regarded as an empirical technology with many aspects of mixing, dispersing and contacting were related to power draw. One important application of solid-liquid mixing is the preparation of brine from sodium formate. This material has been widely used as a drilling and completion fluid in challenging environments such as the Barents Sea. In this paper, large-eddy simulations of a turbulent flow in a solid-liquid baffled cylindrical mixing vessel with large number of solid particles are performed to obtain insight into the fundamental aspects of a mixing tank. The impeller-induced flow at the blade tip radius is modeled by using the... 

    Oscillating pipe flow: high-resolution simulation of nonlinear mechanisms

    , Article 2006 2nd ASME Joint U.S.-European Fluids Engineering Summer Meeting, FEDSM 2006, Miami, FL, 17 July 2006 through 20 July 2006 ; Volume 2006 , 2006 ; 0791837831 (ISBN); 9780791837832 (ISBN) Ghasemi, A ; Sharif University of Technology
    2006
    Abstract
    A new perspective suitable for understanding the details of nonlinear pumping (formation of traveling shocks) inside a pressurized cavity is constructed in this paper. Full compressible axisymmetric three-dimensional Navier-Stokes equations are used as the starting point to cover all complexities of the problem that exceedingly increase for particular ranges of Mach, Reynolds and Prandtl numbers. Then a very high-order numerical method is introduced to preserve the user-defined order of accuracy for practical simulations. For removal of spurious waves, higher-order compact filters are derived. All equations are marched in time using the classical Runge-Kutta algorithm which is appropriate... 

    Numerical simulations of haemodynamic factors and hyperelastic Circumferential Strain/Stress in the ideal and healthy-patient-specific carotid bifurcations for different rheological models

    , Article International Journal of Biomedical Engineering and Technology ; Volume 6, Issue 4 , 2011 , Pages 387-412 ; 17526418 (ISSN) Toloui, M ; Nikparto, A ; Firoozabadi, B ; Saidi, M. S ; Sharif University of Technology
    Abstract
    To explore the role of hemodynamic in the initiation and progression of stenosis in carotid artery bifurcation, a Computational Fluid Dynamics (CFD) technique is applied. The effect of four rheology models is investigated as well as various mechanical phenomena. In this study, a Finite Element Method (FEM) was applied to simulate the physiologic Circumferential Strain/Stress (CS) Meanwhile, to investigate the role of vessel wall flexibility, a Fluid-Structure Interaction (FSI) analysis was applied. It was concluded that velocity profiles and WSS show sensitivity to arterial wall stiffening while shear thinning models do not have a dominant effect on the flow field  

    Finite element modeling of setar, a stringed musical instrument

    , Article 2009 ASME International Mechanical Engineering Congress and Exposition, 13 November 2009 through 19 November 2009 ; Volume 15 , 2010 , Pages 591-597 ; 9780791843888 (ISBN) Mansour, H ; Kasaiezadeh, A ; Arzanpour, S ; Behzad, M ; Sharif University of Technology
    American Society of Mechanical Engineers (ASME) 
    Abstract
    This paper introduces a finite element model of Setar, a Persian long-necked lute. Setar is modeled as a transfer function between the imposed force on the bridge and the near-field resulted sound. Numerical modeling of stringed musical instruments is a computationally challenging task which has always been done with extreme simplifications. Phenomena such as fluid-structure interaction, composite structure, preload effect and infinite boundary are considered in this model. The cycle of Software used in here is CATIA, HyperMesh, Nastran, and HyperGraph. The frequency response between the force of string and generated sound in near field are obtained, taking into account the fluid inside and... 

    Free vibrations of moderately thick truncated conical shells filled with quiescent fluid

    , Article Journal of Fluids and Structures ; Volume 63 , 2016 , Pages 280-301 ; 08899746 (ISSN) Rahmanian, M ; Dehghani Firouz Abadi, R ; Cigeroglu, E ; Sharif University of Technology
    Academic Press  2016
    Abstract
    A novel reduced order formulation is proposed for the vibration analysis of conical shells containing stationary fluid. Hamiltonian approach is followed to obtain the governing equations of motion for the structure. Utilizing the Navier-Stokes equations and simplifying for irrotational, compressible and inviscid assumptions, the final fluid equation is obtained. A general solution based on the Galerkin method is proposed for the conical shell in vacuum. Several boundary conditions are investigated to show the capability of the proposed solution. A novel reduced order formulation based on the finite element method is developed for solution of the fluid equation. Static condensation technique... 

    A multiscale approach for determining the morphology of endothelial cells at a coronary artery

    , Article International Journal for Numerical Methods in Biomedical Engineering ; Volume 33, Issue 12 , 2017 ; 20407939 (ISSN) Pakravan, H. A ; Saidi, M. S ; Firoozabadi, B ; Sharif University of Technology
    Abstract
    The morphology of endothelial cells (ECs) may be an indication for determining atheroprone sites. Until now, there has been no clinical imaging technique to visualize the morphology of ECs in the arteries. The present study introduces a computational technique for determining the morphology of ECs. This technique is a multiscale simulation consisting of the artery scale and the cell scale. The artery scale is a fluid-structure interaction simulation. The input for the artery scale is the geometry of the coronary artery, that is, the dynamic curvature of the artery due to the cardiac motion, blood flow, blood pressure, heart rate, and the mechanical properties of the blood and the arterial...