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porosity
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Effect of wind tunnel wall porosity on the flow around an oscillating airfoil at transonic speeds
, Article Scientia Iranica ; Volume 24, Issue 3 , 2017 , Pages 1069-1076 ; 10263098 (ISSN) ; Soltani, M. R ; Masdari, M ; Sharif University of Technology
Sharif University of Technology
2017
Abstract
The effect of porosity in oscillating situations (to the authors' knowledge, for the first time) on a supercritical airfoil (SC0410) has been experimentally investigated. Tests have been carried out in an open circuit suction-type wind tunnel at a free stream Mach number of M = 0:80. Both static and dynamic (pitching) tests have been carried out on the mentioned airfoil. The oscillation frequency for the unsteady tests has been set to 3 and 6 Hz. The amplitude of frequency is ±1 deg. The effect of porosity has been surveyed on the magnitude of pressure fluctuations, phase shift, and lift coefficient loop. The investigations show that increasing porosity in the test section of transonic...
On modeling of wave propagation in a thermally affected GNP-reinforced imperfect nanocomposite shell
, Article Engineering with Computers ; Volume 35, Issue 4 , 2019 , Pages 1375-1389 ; 01770667 (ISSN) ; Habibi, M ; Safarpour, H ; Sharif University of Technology
Springer London
2019
Abstract
Due to rapid development of process manufacturing, composite materials with porosity have attracted commercial attention in promoting engineering applications. For this regard, in this research wave propagation-thermal characteristics of a size-dependent graphene nanoplatelet-reinforced composite (GNPRC) porous cylindrical nanoshell in thermal environment are investigated. The effects of small scale are analyzed based on nonlocal strain gradient theory (NSGT). The governing equations of the laminated composite cylindrical nanoshell in thermal environment have been evolved using Hamilton’s principle and solved with the assistance of the analytical method. For the first time, wave...
Effect of Porosity on free and forced vibration characteristics of the GPL reinforcement composite nanostructures
, Article Computers and Mathematics with Applications ; Volume 77, Issue 10 , 2019 , Pages 2608-2626 ; 08981221 (ISSN) ; Esmailpoor Hajilak, Z ; Mohammadi, A ; Habibi, M ; Safarpour, H ; Sharif University of Technology
Elsevier Ltd
2019
Abstract
This article investigates the influence of porosity on free and forced vibration characteristics of a nanoshell reinforced by graphene platelets (GPL). The material properties of piece-wise graphene-reinforced composites (GPLRCs) are assumed to be graded in the thickness direction of a cylindrical nanoshell and estimated using a nanomechanical model. In addition, because of imperfection of the current structure, three kinds of porosity distributions are considered. The nanostructure is modeled using modified strain gradient theory (MSGT) which is a size-dependent theory with three length scale parameters. The novelty of the current study is to consider the effects of porosity, GPLRC and MSGT...
High intensity focused ultrasound (HIFU) ablation of porous liver: numerical analysis of heat transfer and hemodynamics
, Article Applied Thermal Engineering ; Volume 170 , April , 2020 ; Firoozabadi, B ; Sharif University of Technology
Elsevier Ltd
2020
Abstract
In the present study, the influence of the liver vascular bed on heat transfer in a tumor located close to the hepatic artery and exposed to high intensity focused ultrasound (HIFU), is studied numerically. For this purpose, an acoustics-thermal-fluid coupling model based on the porous media theory under the local thermal non-equilibrium assumption is used to calculate the temperature field in the tumor, porous liver, and the hepatic artery. Different generations of the liver vasculature including arterial branches, terminal arterial branches, terminal veins and venous branches are examined at different porosities (the volume fraction of the vasculature). It is found that the liver...
The effects of porosity distribution variation on PEM fuel cell performance
, Article Renewable Energy ; Volume 30, Issue 10 , 2005 , Pages 1557-1572 ; 09601481 (ISSN) ; Farhanieh, B ; Saievar Iranizad, E ; Sharif University of Technology
2005
Abstract
Gas diffusion layers (GDL) are one of the important parts of the PEM fuel cell as they serve to transport the reactant gases to the catalyst layer. Porosity of this layer has a large effect on the PEM fuel cell performance. The spatial variation in porosity arises due to two effects: (1) compression of the electrode on the solid landing areas and (2) water produced at the cathode side of gas diffusion layers. Both of these factors change the porosity of gas diffusion layers and affect the fuel cell performance. To implement this performance analysis, a mathematical model which considers oxygen and hydrogen mass fraction in gas diffusion layer and the electrical current density in the...
Experimental Investigation of Brine Salinity Effect on Relative Permeability Curve in Tight Reservoir
, M.Sc. Thesis Sharif University of Technology ; Shad, Saeed (Supervisor)
Abstract
An experimental study was conducted to investigate the reduction of relative permeability caused by salt precipitation. Series of isothermal sand pack flood experiments were conducted on a sand pack composed of several minerals and relative permeability of the involved phases were determined. This compose was taken south of Iranian reservoir properties. A stainless steel sand-pack of 2.5cm internal diameter and 19.2 cm long was designed and built for experimental procedure. There are is different methods to determine relative permeability of porous media, According to available facilities in the lab and objective of this study unsteady state have been chosen to determine relative...
The Effect of Porosity on Photocatalytic Properties of TiO2 Nanocoating Fabricated By Sol-Gel
, M.Sc. Thesis Sharif University of Technology ; Ghorbani, Mohammad (Supervisor)
Abstract
This thesis is concerned with the synthesis and characterization of high porous Ti based on thin films and the effect of polymer agents on their photocatalytic properties. Ti films can demonstrate different properties like self -cleaning and treatment of broad range of aqueous pollutants when it is exposed to light of wavelength less than 400 nm. This is due to photocatalytic reaction occurring on film surface which results in film superhydrophilicity and the active oxygen species production. This active sites and radicals will cause oxidize organic pollutants and microbe adherent to the material surface.
In this study Ti thin films have been prepared by the sol-gel method from...
In this study Ti thin films have been prepared by the sol-gel method from...
Simulation of High Frequency Acoustic Waves in Porous Media
, M.Sc. Thesis Sharif University of Technology ; Farshchi, Moammad (Supervisor)
Abstract
In this study, a numerical investigation of propagation of sound through a fluid-saturated porous column has been proposed so that we can analyze the effects of porous media parameters on decreasing sound amplitude. The mathematical model applied for our simulation is based on Biot equations solved by an explicit finite difference method. Since Biot model is exclusively applicable to porous solids saturated with single fluid phase, in order to simulate a porous solid saturated with two immiscible fluids, we exploited the general Eulerian model instead of Biot model. Efficiency of porous sound absorbers is directly influenced by four major parameters which are porosity, rigidity and thickness...
Experimental Investigation of the Effects of Suction and Wall Porosity on the Surface Pressure and Aerodynamic Forces in Transonic Wind Tunnel
, M.Sc. Thesis Sharif University of Technology ; Soltani, Mohammad Reza (Supervisor)
Abstract
Transonic speed is one of the most important flight regimes. There are two main significances related to it. First, all of the supersonic air vehicles should pass through this regime to reach to their final speed. Second, nowadays most of the commercial airplanes fly in nearsonic speeds. According to nonlinear nature of the flow through the speeds, the related researchers haven’t been successful in development of a comprehensive theory as well as subsonic and supersonic ones. So, transonic flow is one of the most critical regimes in wind tunnel testing. In order to eliminate the shock-boundary layer interaction and wave cancellation, perforated walls and side suction are used in test section...
Neural Network Design and Optimization for Porosity Estimation with Using Seismic Attributs
, M.Sc. Thesis Sharif University of Technology ; Pishvaie, Mahmoud Reza (Supervisor) ; Badakhshan, Amir (Supervisor)
Abstract
Todays, the most important thing in the oil and gas fields is how to find the main properteis as porosity and permeability; therefere in this project was tryed to estimate to correct porosity in the reservoir area with using estimated porosity from siesmic attributes. For this study Mishrif reservoir in Sarvak formation was selected and the used data are 3D siesmic and also corrected porosity estimated by analysing siesmic attributes from five wells. For combination sresmic and log data, Simulated Annealing was seleted as a Neural Network optimizer for this project.
Effects of hydrogen level and cooling rate on ultimate tensile strength of Al A319 alloy
, Article Russian Journal of Non-Ferrous Metals ; Vol. 55, issue. 4 , July , 2014 , p. 365-370 ; 10678212 ; Eisaabadi, G. B ; Davami, P ; Varahram, N ; Shabani, M. O ; Sharif University of Technology
Abstract
The present study investigated the effects of initial Hydrogen level and cooling rate on ultimate tensile strength of commercial Al-A319 alloys. Three hydrogen levels (0.01, 0.2, and 0.41 mL/100 grams of melt) and five cooling rate were studied. Total of 45 tensile test bars was prepared (three hydrogen levels × five cooling rate × three repeats). The UTS of the samples was determined though uniaxial tension tests. Furthermore, the microstructures of the samples were studied by standard metallographic technique and image analysis software. Finally the relationship between UTS and microstructurai features—SDAS and fraction of porosity (Fp%)—of the alloys was investigated.Results of tensile...
Estimation of modulus of elasticity for closed-cell aluminum foam
, Article ASME International Mechanical Engineering Congress and Exposition, Proceedings (IMECE) ; Volume 3, Issue PARTS A, B, AND C , 2012 , Pages 1285-1289 ; 9780791845196 (ISBN) ; Gobal, A ; Alkhani, R ; Sharif University of Technology
2012
Abstract
Monodisperse closed cell aluminum foam was analyzed numerically to determine the relationship between its elastic modulus, porosity and pore diameter. It was found a nonlinear relationship exists between porosity, pore diameter and modulus of elasticity. In this regard, an empirical equation is developed and implemented for the prediction of modulus of elasticity versus porosity and pore diameter. Comparing experimental and analytical approaches by other researchers with those obtained in this research shows agreement exists within 1 to 3 percent
Stress analysis of thermal barrier coating system subjected to out-of-phase thermo-mechanical loadings considering roughness and porosity effect
, Article Surface and Coatings Technology ; Volume 262 , January , 2015 , Pages 77-86 ; 02578972 (ISSN) ; Farrahi, G. H ; Azadi, M ; Ghodrati, M ; Sharif University of Technology
Elsevier
2015
Abstract
This paper presents the out-of-phase thermo-mechanical stress analysis of thermal barrier coating (TBC) system in real working conditions used as thermal barrier in diesel engine cylinder heads. The coating system in this research comprises 350. μm zirconium oxide top coat (TC) and 150. μm metallic bond coat (BC). These layers were deposited on the substrate, aluminum A356 alloy, by the aid of air plasma spray (APS) method. Afterwards, the specimen was subjected to thermo-mechanical fatigue (TMF) loadings. Based on the experimental conditions, FE simulations were performed by both time-independent and time-dependent substrate material properties in ABAQUS software. Simulation results related...
Sintering of biocompatible P/M Co-Cr-Mo alloy (F-75) for fabrication of porosity-graded composite structures
, Article Materials Science and Engineering A ; Volume 472, Issue 1-2 , 2008 , Pages 338-346 ; 09215093 (ISSN) ; Godlinski, D ; Simchi, A ; Firouzdor, V ; Sharif University of Technology
2008
Abstract
Manufacturing of complex-shaped bimetals utilizing two-color powder injection molding (2C-PIM) and three-dimensional printing (3DP) processes, which basically involve sintering of a powder/binder mixture, has been attracted a great interest. This article addresses sintering of biocompatible Co-Cr-Mo alloy for manufacturing stepwise porosity-graded composite structures. Such composite structures provide strength at the core and a porous layer for the tissue growth. To evaluate the process, two grades of gas atomized Co-Cr-Mo powder with an average particle size of 19 and 63 μm were used. Isothermal and non-isothermal sintering behavior of the loose powders under hydrogen and argon...
Immobilization of TiO2 on perlite granules for photocatalytic degradation of phenol
, Article Applied Catalysis B: Environmental ; Volume 74, Issue 1-2 , 2007 , Pages 53-62 ; 09263373 (ISSN) ; Borghei, M ; Vossoughi, M ; Taghavinia, N ; Sharif University of Technology
2007
Abstract
The photocatalytic degradiation of phenol by nanoTiO2 particles coated on perlite as a new composite nano-catalyst was investigated. Titanium dioxide (Degussa P-25) was immobilized on three different supports (perlite granules, glass plates and steel fiber) by a very simple and inexpensive method. Perlite granules have a porosity of more than 95%, which allows them to stay afloat on water surface. This gives the medium a unique characteristic from the processing point of view, which enables it to get wetted with the polluted solution without requiring any pumping and simultaneously be exposed to the radiation source when coated with the photocatalyst. The photocatalytic activity of prepared...
Porosity and permeability effects on centerline temperature distributions, peak flame temperature, flame structure, and preheating mechanism for combustion in porous media
, Article Journal of Energy Resources Technology, Transactions of the ASME ; Volume 129, Issue 1 , 2007 , Pages 54-65 ; 01950738 (ISSN) ; Safavisohi, B ; Sharbati, E ; Sharif University of Technology
2007
Abstract
The applicability and usefulness of combustion in porous media is of much interest due to its competitive combustion efficiency and lower pollutants formation. In the previous works, the focus has been on the effects of combustion and heat transfer parameters such as excess air ratio, thermal power, solid conductivity, convective heat transfer coefficient, and radiation properties on centerline temperature and pollutant formations. A premixed combustion scheme and a fixed porous medium with constant geometrical parameters have been used in these works; therefore, the effects of porous material parameters have been less considered. In this research, the effects of geometrical parameters of...
A study of feasibility for water purification using vertical porous concrete filter
, Article International Journal of Environmental Science and Technology ; Volume 4, Issue 4 , 2007 , Pages 505-512 ; 17351472 (ISSN) ; Torabian, A ; Borghei, M ; Hassani, A. H ; Sharif University of Technology
CEERS
2007
Abstract
There is a need to find cheaper and simpler techniques for rural water filtration system in developing countries. Using a filter made of blocks for the water treatment enables one to make vertical filters. It is expected that the amount of land utilized would decrease by more than 70 % if vertical filters were used. The operation and washing would be simpler than using horizontal sand filters as filters made of blocks would be used instead. The feasibility study focused on finding adequate materials, compositions and methods of making a block with enough resistance to water pressure, sufficient porosity for water transformation, and using inexpensive, readily available materials. A pilot...
Property change during fixtured sintering of NiTi memory alloy
, Article Materials and Manufacturing Processes ; Volume 21, Issue 1 , 2006 , Pages 87-96 ; 10426914 (ISSN) ; Lashkari, O ; Sharif University of Technology
2006
Abstract
Fixtured sintering of up to 5 hours at 1223 to 1323 K is successfully used to diminish the dimensional change of NiTi memory alloys produced from mixtures of elemental Ni and Ti powders packed and pressed at room temperature under 400, 500, and 600 MPa pressure. The improvements obtained can help near-net-shape technology via powder metallurgy that overcomes the traditional casting problems such as oxygen, nitrogen, hydrogen, and carbon absorption and intermetallic compound precipitation, which lower the workability and the homogeneity of the final alloy. The effects of compaction pressure, sintering time, and sintering temperature on dimensional change, porosity, hardness, and morphology of...
Effect of porosity variation in determination of stagnant and dispersion thermal conductivities in the resin transfer molding process
, Article Heat Transfer Research ; Volume 43, Issue 7 , 2012 , Pages 651-667 ; 10642285 (ISSN) ; Rabani, R ; Kermani, M. J ; Sharif University of Technology
2012
Abstract
A numerical analysis for determination of the stagnant and dispersion thermal conductivities in the Resin Transfer Molding (RTM) process is presented. A solution was obtained for the momentum and energy equations, which are used in this study and which represent the Brinkman- Forchheimer-extended Darcy model, and one-temperature energy equation. Subject to the appropriate boundary conditions, the governing equations are solved by the finite volume method on a collocated grid. In order to satisfy the pressure-velocity coupling in the solution, the SIMPLE algorithm was used and for determining the mass flux flowing past the cell faces, the Rhie-Chow interpolation was applied. Both constant and...
Analysis of porosity distribution of large-scale porous media and their reconstruction by Langevin equation
, Article Physical Review E - Statistical, Nonlinear, and Soft Matter Physics ; Volume 83, Issue 2 , February , 2011 ; 15393755 (ISSN) ; Sahimi, M ; Rasaei, M. R ; Tabar, M. R. R ; Sharif University of Technology
Abstract
Several methods have been developed in the past for analyzing the porosity and other types of well logs for large-scale porous media, such as oil reservoirs, as well as their permeability distributions. We developed a method for analyzing the porosity logs φ(h) (where h is the depth) and similar data that are often nonstationary stochastic series. In this method one first generates a new stationary series based on the original data, and then analyzes the resulting series. It is shown that the series based on the successive increments of the log y(h)=φ(h+δh)-φ(h) is a stationary and Markov process, characterized by a Markov length scale hM. The coefficients of the Kramers-Moyal expansion for...