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Numerical study of hydrogen-air combustion characteristics in a novel micro-thermophotovoltaic power generator
, Article Applied Energy ; Volume 199 , 2017 , Pages 382-399 ; 03062619 (ISSN) ; Saidi, M. H ; Sharif University of Technology
Elsevier Ltd
2017
Abstract
In the present work, a micro combustor for thermophotovoltaic (TPV) devices is proposed which is included a U-shaped microtube in a box with a secondary fluid in space between U-shaped microtube and box walls. By utilizing the three-dimensional CFD model, combustion characteristics of the premixed lean hydrogen-air mixture in the present micro combustor are studied numerically with detailed chemistry and transport taking into account heat transfer through the wall. The results show that the establishment of secondary flows and better preheating in the curved tubes is caused the flammability limits to be at least four times in comparison with straight tubes. Combustion characteristics are...
Numerical simulation of buoyancy affected turbulent air flow in a room
, Article Scientia Iranica ; Volume 15, Issue 3 , 2008 , Pages 398-404 ; 10263098 (ISSN) ; Fathi Gishnegani, A ; Sharif University of Technology
Sharif University of Technology
2008
Abstract
In this paper, a three-dimensional steady state incompressible turbulent air flow is considered in a large single room. The buoyancy affected turbulent air flow is numerically simulated by solving governing equations. The turbulence modeling includes both κ - ε and zero-equation models and their results are compared to the experimental data. The paper reviews several aspects, such as displacement of radiator system performance, temperature and flow field distribution and comfort conditions. The results show that the best temperature distribution and comfort condition are obtained when the radiator is installed under the window and its height is equal to or greater than that of the window. ©...
Numerical investigation of a stepped planing hull in calm water
, Article Ocean Engineering ; Volume 94 , January , 2015 , Pages 103-110 ; 00298018 (ISSN) ; Ashrafizaadeh, M ; Esfahan, R. K ; Sharif University of Technology
Elsevier Ltd
2015
Abstract
Stepped planing hulls enable the feasibility of running at relatively low Drag-Lift ratio by means of achieving more optimal trim angle at high speeds. Currently, there is no precise method to analyze these hulls over the full range of operating speeds. In this study, a three-dimensional computational fluid dynamics (CFD) model using volume of fluid (VOF) approach is presented for examining the characteristics of a planing hull having one transverse step. A procedure is presented to transform a series of fixed-position simulations into a free to heave and pitch simulation. Resistance, lift, running draft, dynamic trim angle, and wetted area are compared with available experimental data and...
Numerical investigation and parametric analysis of a photovoltaic thermal system integrated with phase change material
, Article Applied Energy ; Volume 238 , 2019 , Pages 734-746 ; 03062619 (ISSN) ; Salari, A ; Hakkaki Fard, A ; Ma, T ; Sharif University of Technology
Elsevier Ltd
2019
Abstract
In this paper, a comprehensive three-dimensional model of photovoltaic thermal system integrated with phase change material (PVT/PCM) is developed and simulated. The effect of some key parameters using parametric analysis on performance of PVT/PCM system with water as working fluid is investigated. Parameters considered in this study include the properties of PCM (i.e. melting temperature, enthalpy of fusion and thermal conductivity), solar radiation and mass flow rate. The parametric analysis ranges are selected according to the properties of the most of available PCMs on the market, which shows the practical application of the numerical research. Furthermore, a three-dimensional model of...
Numerical assessment of new compound restrainer for seismic retrofit of bridges
, Article Structure and Infrastructure Engineering ; 2017 , Pages 1-20 ; 15732479 (ISSN) ; Pahlavan Yali, A ; Sharif University of Technology
Abstract
This paper studies through numerical simulation a practical compound restrainer to use for the improvement of seismic performance of bridges. A mechanical model has been introduced for the restrainer and a basic optimisation approach has been conducted to evaluate the performance of the restrainer to changes in the properties of its components. A real 2-span simply supported plate girder bridge has been selected for case study. Using a detailed three-dimensional model, several non-linear time history analyses were performed under seismic excitations in order to assess the performance of the bridge retrofitted by conventional restrainers including linear and non-linear viscous dampers on one...
Numerical assessment of new compound restrainer for seismic retrofit of bridges
, Article Structure and Infrastructure Engineering ; Volume 14, Issue 5 , 2018 , Pages 652-671 ; 15732479 (ISSN) ; Pahlavan Yali, A ; Sharif University of Technology
Taylor and Francis Ltd
2018
Abstract
This paper studies through numerical simulation a practical compound restrainer to use for the improvement of seismic performance of bridges. A mechanical model has been introduced for the restrainer and a basic optimisation approach has been conducted to evaluate the performance of the restrainer to changes in the properties of its components. A real 2-span simply supported plate girder bridge has been selected for case study. Using a detailed three-dimensional model, several non-linear time history analyses were performed under seismic excitations in order to assess the performance of the bridge retrofitted by conventional restrainers including linear and non-linear viscous dampers on one...
Nonlinear seismic assessment of steel moment frames under bidirectional loading via endurance time method
, Article Structural Design of Tall and Special Buildings ; Vol. 23, issue. 6 , April , 2014 , p. 442-462 ; ISSN: 15417794 ; Estekanchi, H. E ; Sharif University of Technology
Abstract
In this paper, considering horizontal components of seismic excitation, an algorithm for the nonlinear multi-component analysis of building structures by the Endurance Time (ET) method is proposed, and results of the ET method for various steel moment frames with one to seven stories are verified by comparing with the results from Nonlinear Time History Analysis with use of two different sets of ground motions. In addition, several parameters such as eccentricities and irregularities in structure, rotational and lateral stiffness, effect of hysteresis type and ductility have been considered for sensitivity analysis on results, obtained by ET method. Results show that on the basis of...
New modeling for moment-rotation behavior of bolted endplate connections
, Article Scientia Iranica ; Volume 18, Issue 4 A , August , 2011 , Pages 827-834 ; 10263098 (ISSN) ; Mofid, M ; Sharif University of Technology
2011
Abstract
A new exponential model to depict the moment-rotation (M-θ) relationship of Bolted Endplate Connections (BEC) is proposed. The proposed model represents an approach to the prediction of M-O curves, taking into account the possible failure modes and the deformation characteristics of the connection elements. The presented model has three physical parameters, along with two curve-fitted factors. These physical parameters are generated from dimensional details of the connection, as well as the material properties. By employing simplified connection behavioral models to estimate the connection M-θ behavior, analytical expressions for evaluating major connection parameters, such as initial...
Multi-channel electrocardiogram denoising using a Bayesian filtering framework
, Article 2006 Computers in Cardiology, CIC, Valencia, 17 September 2006 through 20 September 2006 ; Volume 33 , 2006 , Pages 185-188 ; 02766574 (ISSN); 1424425328 (ISBN); 9781424425327 (ISBN) ; Shamsollahi, M. B ; Jutten, C ; Sharif University of Technology
2006
Abstract
In some recent works, model-based filtering approaches have been proved as effective methods for extracting ECG signals from single channel noisy recordings. The previously developed methods, use a highly realistic nonlinear ECG model for the construction of Bayesian filters. In this work, a multi-channel extension of the previous approach is developed, by using a three dimensional model of the cardiac dipole vector. The results have considerable improvement compared with the single channel approach. The method is hence believed to be applicable to low SNR multi-channel recordings
MODSharp: Regional-scale numerical model for quantifying groundwater flux and contaminant discharge into the coastal zone
, Article Environmental Modelling and Software ; Volume 22, Issue 9 , 2007 , Pages 1307-1315 ; 13648152 (ISSN) ; Sharif University of Technology
2007
Abstract
In this paper the development of a quasi-three-dimensional numerical model that can be used for quantifying groundwater inputs and associated contaminant discharged from coastal aquifers into the coastal zone at a regional scale is presented. The present model is called MODSharp. In order to handle problems at a regional scale, the sharp interface approach which is used for conceptualising seawater intrusion, is applied to this model. This model can be used for the simulation of groundwater flow and contaminant transport in layered coastal aquifers at a regional scale. The method of characteristics is used to solve the advection-dispersion equation, which governs contaminant transport in...
Modeling of cell deformation under external force using artificial neural network
, Article ASME International Mechanical Engineering Congress and Exposition, Proceedings (IMECE), 12 November 2010 through 18 November 2010 ; Volume 2 , 2010 , Pages 659-665 ; 9780791844267 (ISBN) ; Vossoughi, G. R ; Abbasi, A. A ; Raeissi, P ; Sharif University of Technology
Abstract
Embryogenesis, regeneration and cell differentiation in microbiological entities are influenced by mechanical forces. Therefore, development of mechanical properties of these materials is important. Neural network technique is a useful method which can be used to obtain cell deformation by the means of force-geometric deformation data or vice versa. Prior to insertion in the needle injection process, deformation and geometry of cell under external point-load is a key element to understand the interaction between cell and needle. In this paper the goal is the prediction of cell membrane deformation under a certain force, and to visually estimate the force of indentation on the membrane from...
Linear and nonlinear model of cutting forces in peripheral milling: A comparison between the accuracy of 2D and 3D models
, Article 2009 ASME International Mechanical Engineering Congress and Exposition, IMECE2009, Lake Buena Vista, FL, 13 November 2009 through 19 November 2009 ; Volume 3 , 2010 , Pages 955-962 ; 9780791843765 (ISBN) ; Movahhedy, M. R ; Vossoughi, G ; Sharif University of Technology
2010
Abstract
Peripheral milling is extensively used in manufacturing processes, especially in aerospace industry where end mills are used for milling of wing parts and engine components. Knowledge of the cutting forces is the first necessary stage in analysis of the milling process. In this paper, cutting forces are presented for both two and three dimensional models. Instead of the common linear dependency of cutting forces to the cut chip thickness, two nonlinear models are presented. In the first model, cutting forces are considered as a function of chip thickness with a complete third order polynomial. In the second one, the quadratic and constant terms of the third order polynomial are set to zero....
Kinetics of static strain aging after temper rolling of low carbon steel
, Article Ironmaking and Steelmaking ; Volume 38, Issue 4 , 2011 , Pages 314-320 ; 03019233 (ISSN) ; Serajzadeh, S ; Sharif University of Technology
Abstract
In this study, static strain aging behaviour of cold rolled steel strips was considered with emphasis on the distribution of residual hydrostatic stress developed during temper rolling. In order to assess residual stress distribution produced by the temper rolling, a three-dimensional model was first employed. Then, samples were rolled at a reduction of 4% under single and double pass rolling programmes and the kinetics of static strain aging phenomenon as well as the required activation energies were then evaluated using hardness and tensile tests on the deformed samples. Considering the predicted residual hydrostatic stress distribution, it was found that tensile hydrostatic stresses...
Investigating the effect of hybrid silica nanoparticles-copolymer on increasing oil recovery in a three dimensional porous media
, Article Scientia Iranica ; Volume 24, Issue 6 , 2017 , Pages 3466-3475 ; 10263098 (ISSN) ; Ramazani, A. S. A ; Hekmatzadeh, M ; Sharif University of Technology
Abstract
In this work, hybrid of silica nanoparticles (NPs) with sulfonated copolymer has been prepared in order to improve the copolymer properties for Enhanced Oil Recovery (EOR). Some tests are done to find the effectiveness of injecting fluid on Recovery Factor (RF), such as Contact Angle (CA), interfacial tension (IFT), inherent viscosity, and eventually Micro-Model (MM) flooding. In CA test, wettability alteration from Oil-Wet (OW) to Water-Wet (WW) is reached by sedimentation and adsorption of NPs on the rock slice. In addition, IFT reduction is obtained by increasing the NaCl concentration. The viscosity change is investigated for the hybrid and copolymer under simulated high-temperature oil...
Hydrodynamic and electrochemical modeling of vanadium redox flow battery
, Article Mechanics and Industry ; Volume 16, Issue 2 , 2015 ; 22577777 (ISSN) ; Elyasi, S ; Mollazadeh, M ; Sharif University of Technology
EDP Sciences
2015
Abstract
Two and three dimensional modeling of a single cell of vanadium redox flow battery has been done thoroughly according to electrochemical and fluid mechanic equations in this study. The modeling has been done in stationary state and its results have been presented in three chemical, electrical and mechanical sub models. The parametric analysis on some of important factors in cell operation demonstrated that increase in electrode and membrane conductivity and electrode porosity contributes to electric potential increase in cells. Also operational temperature increase leads to decrease in cells' voltage. Better fluid distribution on the electrode surface area results in better cell operation,...
Field Scale Characterization of Geological Formations Using Percolation Theory
, Article Transport in Porous Media ; Vol. 92, issue. 2 , March , 2012 , p. 357-372 ; ISSN: 1693913 ; Masihi, M ; Shojaei, A ; Pishvaie, M ; King, P. R ; Sharif University of Technology
Abstract
The connectivity of high conductivity pathways in geological formations depend on the spatial distribution of geological heterogeneities that may appear on various length scales. Appropriate modeling of this is crucial within in hydrology and petroleum systems. The approach taken in this study is to use percolation theory to quantify the connectivity, hydraulic conductivity, and breakthrough time behavior between an injector and a producer within such systems. In particular, a three-dimensional overlapping sandbody model is considered which assumes that the geological formation can be split into either conductive flow units (i. e., good sands) or non-conductive units (i. e., poor sands). The...
Field scale characterization of geological formations using percolation theory
, Article Transport in Porous Media ; Volume 92, Issue 2 , 2012 , Pages 357-372 ; 01693913 (ISSN) ; Masihi, M ; Shojaei, A ; Pishvaie, M ; King, P. R ; Sharif University of Technology
2012
Abstract
The connectivity of high conductivity pathways in geological formations depend on the spatial distribution of geological heterogeneities that may appear on various length scales. Appropriate modeling of this is crucial within in hydrology and petroleum systems. The approach taken in this study is to use percolation theory to quantify the connectivity, hydraulic conductivity, and breakthrough time behavior between an injector and a producer within such systems. In particular, a three-dimensional overlapping sandbody model is considered which assumes that the geological formation can be split into either conductive flow units (i. e., good sands) or non-conductive units (i. e., poor sands). The...
Feasibility of infrared tracking of beating heart motion for robotic assisted beating heart surgery
, Article International Journal of Medical Robotics and Computer Assisted Surgery ; Volume 14, Issue 1 , February , 2018 ; 14785951 (ISSN) ; Farahmand, F ; Vossoughi, G ; Ghavidel, A. A ; Rezayat, M ; Sharif University of Technology
John Wiley and Sons Ltd
2018
Abstract
Background: Accurate tracking of the heart surface motion is a major requirement for robot assisted beating heart surgery. Method: The feasibility of a stereo infrared tracking system for measuring the free beating heart motion was investigated by experiments on a heart motion simulator, as well as model surgery on a dog. Results: Simulator experiments revealed a high tracking accuracy (81 μm root mean square error) when the capturing times were synchronized and the tracker pointed at the target from a 100 cm distance. The animal experiment revealed the applicability of the infrared tracker with passive markers in practical heart surgery conditions. Conclusion: With the current technology,...
Experimental and theoretical evaluations of thermal histories and residual stresses in dissimilar friction stir welding of AA5086-AA6061
, Article International Journal of Advanced Manufacturing Technology ; Volume 61, Issue 1-4 , 2012 , Pages 149-160 ; 02683768 (ISSN) ; Serajzadeh, S ; Kokabi, A. H ; Sharif University of Technology
2012
Abstract
In this work, the thermomechanical responses during the dissimilar friction stir welding of aluminum alloys have been evaluated employing a three-dimensional model and the finite element software ABAQUS. Furthermore, welding experiments have been conducted under different working conditions and the temperature variations during and after welding as well as the produced residual stresses in various positions of the welded samples were measured using hole-drilling technique. The model results were then examined by experimental data, and a reasonable agreement was observed. It is found that tool rotational speed significantly affects the amount of maximum tensile residual stress while traverse...
Experimental and numerical study of low frequency pulsed Nd:YAG laser heating of slip cast fused silica ceramics for laser assisted turning process considering laser beam overlapping
, Article Scientia Iranica ; Volume 26, Issue 1B , 2019 , Pages 394-407 ; 10263098 (ISSN) ; Movahhedy, M. R ; Shoja Razavi, R ; Sharif University of Technology
Sharif University of Technology
2019
Abstract
Machining of ceramics often involves many challenges due to their high hardness, brittleness, and low-thermal conductivity. Laser Assisted Machining (LAM) is a promising technology for improving the machinability of hard-to-cut materials. In this work, the effect of laser heating in the LAM process on Slip Cast Fused Silica (SCFS) ceramics is investigated by conducting a numerical thermal analysis of laser effects on material behavior. A transient three-dimensional heat transfer analysis for Laser Assisted Turning (LAT) of SCFS is performed using finite-element method. Temperature distributions in SCFS cylindrical specimens are obtained. Moreover, the influence of laser parameters, such as...