Search for: computational-mechanics
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    Design, modeling and optimization of a novel two DOF polymeric electro-thermal micro-actuator

    , Article Applied Mechanics and Materials ; Vol. 307 , 2013 , pp. 112-116 ; ISSN: 16609336 ; ISBN: 9783037856598 Sheikhbahaie, R ; Alasty, A ; Salarieh, H ; Sharif University of Technology
    In this paper, design, simulation and optimization of a novel electrothermally-activated polymeric microactuator capable of generating combination of bidirectional lateral and rotational motions are presented. The composite structure of this actuator is consisted of a symmetric meandered shape silicon skeleton, a SU8 thermal expandable polymer and a thin film chrome layer heater. This actuator is controlled by applying appropriate voltages on its four terminals. With the purpose of dimension optimization, a numerical parametric study is executed. The modeled actuator which is 1560 ?m long, 156 ?m wide and 30 ?m thick, demonstrates a remarkable lateral displacement of 23 ?m at power... 

    Numerical studies on the performance of Saccardo ventilation system in emergency fire scenarios

    , Article Applied Mechanics and Materials ; Vol. 527 , 2014 , Pages 146-151 ; ISSN: 16609336 Ganjiazad, R ; Kazemipour, A ; Afshin, H ; Farhanieh, B ; Sharif University of Technology
    In this study, the influence of volumetric flow rate and inclination angle of air jet is evaluated on the performance of a Saccardo ventilation system in a straight rectangular tunnel in case of fire. Simultaneous effects of volumetric flow rate and inclination angle of jet exiting the Saccardo nozzle on the behavior of smoke plume is considered by studying the structure of velocity profile before the fire source. It is found that this factor has a remarkable influence on the behavior of smoke plume and therefore, on the temperatures experienced near the fire. Besides, the influence of tunnel slope on the performance of the Saccardo system to sweep the plume is investigated. It is shown that... 

    Investigation of cutting model in machining of Al/SiC p metal matrix composite

    , Article Applied Mechanics and Materials, 18 November 2011 through 20 November 2011, Shenzhen ; Volume 117-119 , 2012 , Pages 1465-1470 ; 16609336 (ISSN) ; 9783037852804 (ISBN) Nikouei, S. M ; Kouchakzadeh, M. A ; Yousefi, R ; Kadivar, M. A ; Sharif University of Technology
    Prediction of shear plane angle is a way for prediction of the mechanism of chip formation, machining forces and so on. In this study, Merchant and Lee-Shaffer theories are used to predict the shear plane angles and cutting forces in machining of Al/SiC p MMC. The experimental cutting forces are compared with the calculated cutting force based on shear plane angles extracted from Merchant and Lee-Shaffer theories. The variation of these cutting forces with cutting speed, feed rate and depth of cut has been discussed. The results show that Merchant theory may be used as a good method for prediction of chip formation in machining of Al/SiC p MMC  

    Development of 3D neutron noise simulator based on GFEM with unstructured tetrahedron elements

    , Article Annals of Nuclear Energy ; Volume 97 , 2016 , Pages 132-141 ; 03064549 (ISSN) Hosseini, S. A ; Vosoughi, N ; Sharif University of Technology
    Elsevier Ltd 
    In the present study, the neutron noise, i.e. the stationary fluctuation of the neutron flux around its mean value is calculated based on the 2G, 3D neutron diffusion theory. To this end, the static neutron calculation is performed at the first stage. The spatial discretization of the neutron diffusion equation is performed based on linear approximation of Galerkin Finite Element Method (GFEM) using unstructured tetrahedron elements. Using power iteration method, neutron flux and corresponding eigen-value are obtained. The results are then benchmarked against the valid results for VVER-1000 (3D) benchmark problem. In the second stage, the neutron noise equation is solved using GFEM and... 

    Generalized nonlinear 3D Euler-Bernoulli beam theory

    , Article Iranian Journal of Science and Technology, Transaction B: Engineering ; Volume 32, Issue 1 , 2008 , Pages 1-12 ; 10286284 (ISSN) Zohoor, H ; Khorsandijou, S. M ; Sharif University of Technology
    The issue of the new elastic terms discovered in the nonlinear dynamic model of an enhanced nonlinear 3D Euler-Bernoulli beam is discussed. While the elastic orientation is negligible, the nonlinear dynamic model governing tension-compression, torsion and two spatial bendings is presented. Considering this model, some new elastic terms can be identified in the variation of elastic potential energy in each bending motion equation, and in each transverse shear force. Due to the new terms, each term of a bending equation and a transverse shear force, finds a counterpart in the other bending equation and transverse shear force, but the equations remain asymmetric. The new terms have arisen,... 

    Experimental and computational investigation into the use of co-flow fluidic thrust vectoring on a small gas turbine

    , Article Aeronautical Journal ; Volume 112, Issue 1127 , 2008 , Pages 17-25 ; 00019240 (ISSN) Banazadeh, A ; Saghafi, F ; Ghoreyshi, M ; Pilidis, P ; Sharif University of Technology
    Royal Aeronautical Society  2008
    This paper presents the application of a relatively new technique of fluidic thrust-vectoring (FTV), named Co-flow, for a small gas-turbines. The performance is obtained via experiment and computational fluid dynamics (CFD). The effects of a few selected parameters including the engine throttle setting, the secondary air mass-flow rate and the secondary slot height upon thrust-vectoring performance are provided. Thrust vectoring performance is characterised by the ability of the system to deflect the engine thrust with respect to the delivered secondary air mass-flow rate. The experimental study was conducted under static conditions in an outdoor environment at Cranfield University workshop... 

    Applying simulated annealing to cellular manufacturing system design

    , Article International Journal of Advanced Manufacturing Technology ; Volume 32, Issue 5-6 , 2007 , Pages 531-536 ; 02683768 (ISSN) Arkat, J ; Saidi, M ; Abbasi, B ; Sharif University of Technology
    Cell formation and cellular layout design are the two main steps in designing a cellular manufacturing system (CMS). In this paper, we will present an integrated methodology based on a new concept of similarity coefficients and the use of simulated annealing (SA) as an optimization tool. In comparison with the previous works, the proposed methodology takes into account relevant production data, such as alternative process routings and the production volumes of parts. The SA-based optimization tool is parallel in nature and, hence, can reduce the computation time significantly, so it is capable of handling large-scale problems. Finally, the SA-based procedure is compared with a genetic... 

    Hierarchical Multi-Scale Modeling of Large Plastic Deformation with Application in Powder Compaction

    , Ph.D. Dissertation Sharif University of Technology Rezaei Sameti, Amir (Author) ; Khoei, Amir Reza (Supervisor)
    The hierarchical multi-scale approach is one of the most powerful techniques that takes the advantage of different scales and succeeds the limitations of each method in a way that the large systems in coarse-scale can be simulated with atomic precision. In this thesis, the hierarchical atomistic-continuum multi-scale method is developed for modeling the phenomena with non-homogenous deformation, large deformation and plastic behavior. In this regard at first, an atomistic-based higher-order continuum model is formulated in the framework of nonlinear finite element method to present the geometrically nonlinear behavior of nano-structures. The efficiency of higher-order Cauchy-Born hypothesis... 

    EFG mesh-less method for coupled hydro-mechanical analysis of unsaturated porous media

    , Article Unsaturated Soils: Research and Applications - Proceedings of the 6th International Conference on Unsaturated Soils, UNSAT 2014 ; Vol. 1, issue , July , 2014 , p. 581-587 ; 978-1-138-00150-3 Samimi, S ; Pak, A ; Sharif University of Technology
    Numerical modeling of the fully coupled phenomena of solid deformation-fluid flow in partially saturated porous media is of great interest in many branches of science and engineering. In this study, a new formulation based on one of the famous mesh-less methods, called Element-Free Galerkin (EFG), is developed to simulate the water and air movement through variably saturated soils. For this purpose, the governing partial differential equations including the equilibrium equation and mass conservation laws for each fluid phase are discretized in space using the same EFG shape functions. To enforce the essential boundary conditions, penalty method is employed. Temporal discretization is... 

    Mixing enhancement of two gases in a microchannel using DSMC

    , Article Applied Mechanics and Materials, Dubai ; Volume 307 , 2013 , Pages 166-169 ; 16609336 (ISSN) ; 9783037856598 (ISBN) Darbandi, M ; Lakzian, E ; Sharif University of Technology
    In high Knudsen number flow regimes microgas flow analysis may not be performed accurately using the classical CFD methods. Alternatively, the gas flow through micro-geometries can be investigated reliably using the direct simulation Monte Carlo (DSMC) method. Our concern in this paper is to use DSMC to study the mixing of two gases in entering simultaneously into a microchannel. The mixing process is assumed to be complete when the mass composition of each species deviates by no more than ±1% from its equilibrium composition. To enhance the mixing process, we focus on the effects of inlet-outlet pressure difference and the pressure ratios of the two incoming CO and N2 streams on the mixing... 

    CFD simulation of natural draught cooling tower wind-covering

    , Article Applied Mechanics and Materials, Dubai ; Volume 307 , 2013 , Pages 279-284 ; 16609336 (ISSN) ; 9783037856598 (ISBN) Darbandi, M ; Salemkar, H ; Behrouzifar, A ; Abrar, B ; Sharif University of Technology
    Past experiences have shown that a local wind can considerably affect the performances of powerplant cooling towers and factory chimneys. In thermal powerplants, the performance of Rankin cycles would reduce if the temperature of its condenser increases. This issue is very important to powerplants located in countries with strong local winds. To remedy the malperformance of a natural cooling tower in windy conditions, it is required to understand the physics of flow around cooling towers more clearly. One adverse physics is known as the wind covering problem which can drastically affect the natural draught through a cooling tower in windy conditions. In this paper, we focus on wind-covering... 

    3D neutron diffusion computational code based on GFEM with unstructured tetrahedron elements: A comparative study for linear and quadratic approximations

    , Article Progress in Nuclear Energy ; Volume 92 , 2016 , Pages 119-132 ; 01491970 (ISSN) Hosseini, S. A ; Sharif University of Technology
    Elsevier Ltd  2016
    In the present study, the comparison between the results obtained from the linear and quadratic approximations of the Galerkin Finite Element Method (GFEM) for neutronic reactor core calculation was reported. The sensitivity analysis of the calculated neutron multiplication factor, neutron flux and power distributions in the reactor core vs. the number of the unstructured tetrahedron elements and order of the considered shape function was performed. The cost of the performed calculation using linear and quadratic approximation was compared through the calculation of the FOM. The neutronic core calculation was performed for both rectangular and hexagonal geometries. Both the criticality and... 

    Toward multiscale modeling of wave propagation in arteries

    , Article Journal of Mechanics in Medicine and Biology ; Volume 16, Issue 3 , 2016 ; 02195194 (ISSN) Raustin, R ; Mohammadi, H ; Sharif University of Technology
    World Scientific Publishing Co. Pte Ltd 
    In this study, we apply a novel numerical technique for modeling the propagation of mechanical wave in the human arteries using the multiscale method. We define a particle region characterized by molecular dynamics (MD) method which is surrounded by a continuous region characterized by a finite element (FE) method. The interface between the two models are defined so as to minimize spurious reflections at the interface. This is a preliminary work for the modeling of the mechanical stability of atherosclerosis plaques using multiscale method. The model offered has extensive application in cell mechanics  

    An integrated SPH-polyhedral DEM algorithm to investigate hydraulic stability of rock and concrete blocks: application to cubic armours in breakwaters

    , Article Engineering Analysis with Boundary Elements ; Volume 84 , 2017 , Pages 1-18 ; 09557997 (ISSN) Sarfaraz, M ; Pak, A ; Sharif University of Technology
    In this paper, a combination of the Lagrangian meshfree method of SPH and Polyhedral DEM is presented to simulate the interaction between the free surface of water and solid objects possessing sharp edges and flat surfaces, such as armour units of breakwaters. Both SPH and DEM schemes are validated successfully against experimental data. The numerical scheme is utilized to inspect the stability of concrete cubic armours in rubble-mound breakwaters through systematic analyses with various geometrical parameters and environmental conditions. The numerical results regarding the required dimensions of the cubic blocks for providing stability of the armour units under the wave attack are compared... 

    Multi-scale modeling of plastic deformations in nano-scale materials; transition to plastic limit

    , Article International Journal for Numerical Methods in Engineering ; Volume 109, Issue 8 , 2017 , Pages 1180-1216 ; 00295981 (ISSN) Khoei, A. R ; Jahanshahi, M ; Sharif University of Technology
    A large amount of research in computational mechanics has biased toward atomistic simulations. This trend, on one hand, is due to the increased demand to perform computations in nanoscale and, on the other hand, is due to the rather simple applications of pairwise potentials in modeling the interactions between atoms of a given crystal. The Cauchy–Born (CB) hypothesis has been used effectively to model the behavior of crystals under different loading conditions, in which the comparison with molecular dynamics simulations presents desirable coincidence between the results. A number of research works have been devoted to the validity of CB hypothesis and its application in post-elastic limit.... 

    An investigation on the dynamic response of the shaking table steel deck using finite element

    , Article 11th World Congress on Computational Mechanics, WCCM 2014, 5th European Conference on Computational Mechanics, ECCM 2014 and 6th European Conference on Computational Fluid Dynamics, ECFD 2014 ; 2014 , pp. 1330-1340 ; ISBN: 9788494284472 Moghaddam, H ; Farzanian, K ; Taheri, E ; Sharif University of Technology
    This paper presents the results of an analytical study on the dynamic characteristics of the Shaking Table facilities at Sharif University. This 3 degree of freedom shaking table is driven by 3 servo-control hydraulic actuators, and consists of a 12 ton, 4m×4m×0.6m steel deck. The main objective of this investigation is to identify the degree of flexibility of the deck, and its adverse effects in causing errors in the simulation of seismic effects on different structural specimens. Many frame specimens of different weights and configurations are subjected to seismic motions, and their responses are calculated using FE models. Some of these models were designed to account for eccentric... 

    A novel three-dimensional element free Galerkin (EFG) code for simulating two-phase fluid flow in porous materials

    , Article Engineering Analysis with Boundary Elements ; Vol. 39, issue. 1 , 2014 , pp. 53-63 ; ISSN: 09557997 Samimi, S ; Pak, A ; Sharif University of Technology
    In the past few decades, numerical simulation of multiphase flow systems has received increasing attention because of its importance in various fields of science and engineering. In this paper, a three-dimensional numerical model is developed for the analysis of simultaneous flow of two fluids through porous media. The numerical approach is fairly new based on the element-free Galerkin (EFG) method. The EFG is a type of mesh-less method which has rarely been used in the field of flow in porous media. The weak forms of the governing partial differential equations are derived by applying the weighted residual method and Galerkin technique. The penalty method is utilized for imposition of the... 

    A fully coupled element-free Galerkin model for hydro-mechanical analysis of advancement of fluid-driven fractures in porous media

    , Article International Journal for Numerical and Analytical Methods in Geomechanics ; Volume 40, Issue 16 , 2016 , Pages 2178-2206 ; 03639061 (ISSN) Samimi, S ; Pak, A ; Sharif University of Technology
    John Wiley and Sons Ltd 
    Hydraulic fracturing (HF) of underground formations has widely been used in different fields of engineering. Despite the technological advances in techniques of in situ HF, the industry uses semi-analytical tools to design HF treatment. This is due to the complex interaction among various mechanisms involved in this process, so that for thorough simulations of HF operations a fully coupled numerical model is required. In this study, using element-free Galerkin (EFG) mesh-less method, a new formulation for numerical modeling of hydraulic fracture propagation in porous media is developed. This numerical approach, which is based on the simultaneous solution of equilibrium and continuity... 

    A three-dimensional mesh-free model for analyzing multi-phase flow in deforming porous media

    , Article Meccanica ; Volume 51, Issue 3 , 2016 , Pages 517-536 ; 00256455 (ISSN) Samimi, S ; Pak, A ; Sharif University of Technology
    Springer Netherlands 
    Fully coupled flow-deformation analysis of deformable multiphase porous media saturated by several immiscible fluids has attracted the attention of researchers in widely different fields of engineering. This paper presents a new numerical tool to simulate the complicated process of two-phase fluid flow through deforming porous materials using a mesh-free technique, called element-free Galerkin (EFG) method. The numerical treatment of the governing partial differential equations involving the equilibrium and continuity equations of pore fluids is based on Galerkin’s weighted residual approach and employing the penalty method to introduce the essential boundary conditions into the weak forms.... 

    Extrinsically enriched element free Galerkin method for heat and fluid flow in deformable porous media involving weak and strong discontinuities

    , Article Computers and Geotechnics ; Volume 103 , 2018 , Pages 179-192 ; 0266352X (ISSN) Iranmanesh, M. A ; Pak, A ; Sharif University of Technology
    Elsevier Ltd  2018
    In this study, an extrinsically enriched element free Galerkin (EFG) method is proposed for the thermo-hydro-mechanical simulation of saturated porous media. By taking advantage of partition of unity property of moving least square shape functions, weak discontinuities such as material interfaces are modeled using the Ridge enrichment function and impermeable strong discontinuities are simulated using the Heaviside function. Some guidelines are proposed for the selection of EFG numerical parameters to ensure the stability and accuracy of the results. Numerical examples are provided to illustrate the capability of the proposed approach for fully coupled THM analysis of discontinuous porous...