Search for: semi-analytical
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    Implementing an accurate generalized gaussian quadrature solution to find the elastic field in a homogeneous anisotropic media

    , Article Journal of the Serbian Society for Computational Mechanics ; Volume 11, Issue 1 , 2017 , Pages 11-19 ; 18206530 (ISSN) Kabir, H ; Matikolaei, S. A. H. H ; Sharif University of Technology
    In the current study, the elastic field in an anisotropic elastic media is determined by implementing a general semi-analytical method. In this specific methodology, the displacement field is computed as a sum of finite functions with unknown coefficients. These aforementioned functions exactly satisfy both the homogeneous and inhomogeneous boundary conditions in the proposed media. It is worth mentioning that the unknown coefficients are determined by implementing the principle of minimum potential energy. The numerical integration is done by employing the Generalized Gaussian Quadrature rule. Furthermore, and with the aid of the calculated unknown coefficients, the displacement fields as... 

    Vibration analysis of a variable thickness isotropic Kirchhoff annular plate covered with piezoelectric layers using modified wave method

    , Article Australian Journal of Basic and Applied Sciences ; Volume 5, Issue 8 , August , 2011 , Pages 1172-1184 ; 19918178 (ISSN) Rasekh Saleh, N ; Bahrami, M. N ; Kargarnovin, M. H ; Sharif University of Technology
    In this paper, based on Kirchhoff plate theory (CLPT), vibration analysis of an arbitrary nonlinear variable thickness annular isotropic plate which is covered with piezoelectric layers on the top and bottom surfaces in a short circuit state is performed using a semi-analytic method, named modified wave method (MWM). The plate is partitioned into several continuous segments with constant thicknesses, for which there exists exact analytical solutions. Considering wave method, the solution of each segment is assumed to be the combination of waves moving forward and backward, and at each step, waves in positive and negative directions are obtained in terms of waves at the inner edge of the... 

    On dynamic pull-in instability of electrostatically actuated multilayer nanoresonators: A semi-analytical solution

    , Article ZAMM Zeitschrift fur Angewandte Mathematik und Mechanik ; Volume 99, Issue 9 , 2019 ; 00442267 (ISSN) Taati, E ; Sharif University of Technology
    Wiley-VCH Verlag  2019
    Based on the nonlocal Euler–Bernoulli beam theory, a theoretical approach is developed to investigate the effects of small scale and intermolecular force on the dynamic pull-in behavior of electrostatically actuated nanoresonators. To this purpose, nanoresonators are modeled as multilayer beams with rectangular cross-sections and fixed-fixed and fixed-free end conditions which are embedded in an elastic medium containing Winkler and Pasternak elastic foundations. Also, the effects of nonlocal parameter, fringing field due to the finite width of beams, Casimir or van der Waals intermolecular forces, nonlinear term induced by mid-plane stretching and Winkler and Pasternak elastic foundations... 

    Semi analytical solution to transient start of weakly underexpanded turbulent jet

    , Article Journal of Fluids Engineering, Transactions of the ASME ; Volume 133, Issue 9 , Sep , 2011 ; 00982202 (ISSN) Chitsaz, I ; Saidi, M. H ; Mozafari, A. A ; Sharif University of Technology
    This study presents a semi analytical solution for the transient weakly underexpanded jet. Different polytropic processes are compared with available experimental data in the literature to assess the best process for steady and transient weakly underexpanded jets. The steady state results agree reasonably well with the experimental and analytical data. It is also shown that isentropic process evaluates steady injection better than other processes. Tip penetration of transient results was compared with available data in literature, and no exact agreement for isothermal and isentropic is observed. This appears due to the linearization of equation of state. It is suggested that more accurate... 

    Analysis and Design of Optical Devices by Colloidal Nano-Structures

    , M.Sc. Thesis Sharif University of Technology Nekuee, Amir Hossein (Author) ; Akbari, Mahmood (Supervisor)
    The colloidal crystals are formed of spherical particles and can be fabricated using simple and low-cost chemical methods. Optical properties of colloidal crystals should be recognized properly in order to design optical devices based on these nano-structures. Reflection and transmission coefficients of these multilayer structures are very important for understanding their properties. Semi-analytical methods like Fourier Modal method (FMM) can be very useful to obtain their reflection and transmission properties of these multilayer structures. In this thesis, we try to implement Matched Coordinate (MC) and Adaptive Spatial Resolution (ASR) techniques in the FMM. These techniques increase... 

    Three Dimensional Double Diffusive Convection in Saturated Porous Media

    , M.Sc. Thesis Sharif University of Technology Tabrizi Nejad As, Sara (Author) ; Aataiee-Ashtiani, Behzad (Supervisor)
    Thermal and compositional variations through porous media are the main causes of bringing changes in the density of the fluid in place and arising in density-driven flow. This phenomenon is usually called thermohaline or thermosolutal convection (TC). When the flow is driven by the concentration gradient of two different compositions the problem is called double-diffusive convection (DDC). This phenomenon can be observed in several applications as in geological carbon dioxide sequestration, geothermal systems, underground thermal energy storage, salt mining, salt domes, groundwater management, waste disposal, and seawater intrusion.Despite that TC processes are three-dimensional by nature... 

    Developing Three Dimensional Model for Delineation of Capture Zone of Multi Wells in Complicated Condition (Skin Effect, Partially Penetrating)

    , M.Sc. Thesis Sharif University of Technology Rashidian dezfouli, Hassan (Author) ; Ataei Ashtiani, Behzad (Supervisor)
    Pump and treat is one of the oldest and mostly used methods in remediation of groundwater. Although this method has been criticized recently, it is still widely be used. The systems typically use one or more extraction and injection wells to hydraulically control the contamination plume. The purpose of studying a pump and treat system is to determine the appropriate location and discharge for the wells in the way that the contamination could be pumped out. In this study after reviewing some existing solutions for delineation the capture zone of single well a method to delineate the capture zone for arbitrary located wells is presented. This method can delineate a three dimensional capture... 

    Time-Dependent Stress of Functionally Graded Rotating Disks

    , M.Sc. Thesis Sharif University of Technology Livani, Mostafa (Author) ; Haddadpoor, Hassan (Supervisor) ; Hoseini Koordkheili, Ali (Supervisor)
    A semi-analytical solution for rotating axisymmetric disks made of functionally graded materials was previously proposed by Hosseini Kordkheili and Naghdabadi [10]. In the present work the solution is employed to study thermoelastic creep behavior of the functionally graded rotating disks with variable thickness in to the time domain. The rate type governing differential equations for the considered structure are derived and analytically solved in terms of rate of stress and strain as a reduced to a set of linear algebraic equations. The advantage of this method is to avoid simplifications and restrictions which are normally associated with other creep solution techniques in the literature.... 

    Free vibration analysis of moderately thick functionally graded plates on elastic foundation using the extended Kantorovich method

    , Article Archive of Applied Mechanics ; Volume 83, Issue 2 , February , 2013 , Pages 177-191 ; 09391533 (ISSN) Fallah, A ; Aghdam, M. M ; Kargarnovin, M. H ; Sharif University of Technology
    Free vibration analysis of moderately thick rectangular FG plates on elastic foundation with various combinations of simply supported and clamped boundary conditions are studied. Winkler model is considered to describe the reaction of elastic foundation on the plate. Governing equations of motion are obtained based on the Mindlin plate theory. A semi-analytical solution is presented for the governing equations using the extended Kantorovich method together with infinite power series solution. Results are compared and validated with available results in the literature. Effects of elastic foundation, boundary conditions, material, and geometrical parameters on natural frequencies of the FG... 

    Experimental investigation of near miscibility effect on relative permeability curves

    , Article 74th European Association of Geoscientists and Engineers Conference and Exhibition 2012 Incorporating SPE EUROPEC 2012: Responsibly Securing Natural Resources, 4 June 2012 through 7 June 2012 ; June , 2012 , Pages 5469-5474 ; 9781629937908 (ISBN) Parvazdavani, M ; Masihi, M ; Ghazanfari, M. H ; Sharif University of Technology
    European Association of Geoscientists and Engineers, EAGE  2012
    The requirement of reliable relative permeability data is more intensified when the miscibility condition approaches. In this work the relative permeability of CO2 and oil has been measured at different miscibility conditions using conventional methods. Fractured dolomite and sandstone core plugs samples were used in the experiments. Due to some errorful assumptions of conventional methods such as immiscible, incompressible displacement, inverse modeling was used for predicting the reliable relative permeability of oil and gas phases at near miscible condition from measured oil production and pressure drop data. The initial guesses of relative permeabilities were provided from conventional... 

    Analytical and rigorous method for analysis of an array of magnetically-biased graphene ribbons

    , Article Optics Express ; Volume 27, Issue 20 , 2019 ; 10944087 (ISSN) Rahmanzadeh, M ; Rejaei, B ; Memarian, M ; Khavasi, A ; Sharif University of Technology
    OSA - The Optical Society  2019
    A sheet of graphene under magnetic bias attains anisotropic surface conductivity, opening the door for realizing compact devices such as Faraday rotators, isolators and circulators. In this paper, an accurate and analytical method is proposed for a periodic array of graphene ribbons under magnetic bias. The method is based on integral equations governing the induced surface currents on the coplanar array of graphene ribbons. For subwavelength size ribbons subjected to an incident plane wave, the current distribution is derived leading to analytical expressions for the reflection/transmission coefficients. The results obtained are in excellent agreement with full-wave simulations and predict... 

    Effect of residual stress on stress intensity factors of fretting fatigue cracks

    , Article International Journal of Microstructure and Materials Properties ; Volume 2, Issue 2 , 2007 , Pages 164-177 ; 17418410 (ISSN) Farrahi, G. H ; Mohajerani, A ; Sharif University of Technology
    Inderscience Publishers  2007
    The effect of compressive Residual Stress (RS) on the Stress Intensity Factors (SIFs) of fretting fatigue cracks was studied using semi-analytical methods. The fretting fatigue of a half-plane in contact with a flat rounded pad was taken into consideration, and RS such as those created by shot-peening were added to the model. Studies of several RS profiles were accomplished to consider the effect of changes in RS caused by stress relaxation during service or pretreatment and manufacturing discrepancies regarding parameters. The distribution of dislocations method was applied to the calculation of the SIFs of these cracks and was shown to be capable of dealing with these kinds of problems. It... 

    Semi-analytical solution for the free vibration analysis of generally laminated composite Timoshenko beams with single delamination

    , Article Composites Part B: Engineering ; Volume 45, Issue 1 , 2013 , Pages 587-600 ; 13598368 (ISSN) Kargarnovin, M. H ; Ahmadian, M. T ; Jafari Talookolaei, R. A ; Abedi, M ; Sharif University of Technology
    A rather new semi-analytical method towards investigating the free vibration analysis of generally laminated composite beam (LCB) with a delamination is presented. For the first time the combined effects of material couplings (bending-tension, bending-twist, and tension-twist couplings) with the effects of shear deformation, rotary inertia and Poisson's effect are taken into account. The semi-analytical solution for the natural frequencies and mode shapes are presented by incorporating the constraint conditions using the method of Lagrange multipliers. To verify the validity and the accuracy of the obtained results, they were compared with the results from other available references. Very... 

    Stable semi-analytical method for analysis of plasmonic propagation on periodically patterned metal plates

    , Article Proceedings of SPIE - The International Society for Optical Engineering, 26 January 2010 through 28 January 2010 ; January , 2010 ; 0277786X (ISSN) ; 9780819480057 (ISBN) Yasrebi, N ; Khorasani, S ; Karami Taheri, H ; Rashidian, B ; Hosseini, A ; Sharif University of Technology
    The need for antennas with improved characteristics for communication and radar applications has resulted in an ever-increasing demand for research in the field of high impedance surfaces, which can work as an artificial magnetic conductor. One method in fabrication of these surfaces is formation of a metamaterial by patterning a metallic surface in the shape of space filling curves (e.g. Hilbert or Peanu Curves). In this paper, we present a novel semi-analytical solution to the problem of plasmonic propagation on these surfaces. The method is based on a previously presented Green's function formalism, which has been reported in an earlier paper of ours. We have modified and improved the... 

    Numerical investigation of crack orientation in the fretting fatigue of a flat rounded contact

    , Article International Journal of Engineering, Transactions B: Applications ; Volume 23, Issue 3-4 , 2010 , Pages 223-232 ; 1728-144X (ISSN) Mohajerani, A ; Farrahi, G. H ; Sharif University of Technology
    Materials and Energy Research Center  2010
    The growth of slant cracks by fretting fatigue of a half plane in contact with a flat rounded pad was studied. The mode I and mode II stress intensity factors for cracks of various lengths and directions were calculated using the semi-analytical method of the distribution of dislocations, and their cumulative effect on the crack growth was investigated using the strain energy density criterion. The results showed dominance of mode I fracture on crack growth, and based on the observation of strain energy density factor versus crack orientation, the results also suggest that depending on the crack length, the most critical orientations of cracks are at 0° to 20° outward the contact zone. Good... 

    Tree-dimensional Free Vibration of Nano-Composite Plates with Arbitrary Geometry within Couple Stress Theory

    , M.Sc. Thesis Sharif University of Technology Forouzan, Bahareh (Author) ; Mohammadi Shoja, Hossein (Supervisor)
    Based on Hamilton’s principle, a three-dimensional semi-analytical method for the analysis of free vibration of a nano-composite plate within the couple stress theory is developed. Computation of dynamic behavior as well as natural frequencies and mode shapes is interested. In this method, the mechanical displacement functions, in each layer, are defined as product of a base function and a three-dimensional polynomial with unknown coefficients. The base functions are defined with respect to the kinematical boundary condition and the domain geometry. The mode shapes will be obtained and the accuracy of the present approach is demonstrated by comparison it in both classical elasticity and... 

    Obtaining a Semi-analytical Solution for Contaminant Transport in Coastal Aquifers: Fourier-galerkin Method

    , M.Sc. Thesis Sharif University of Technology Koohbor, Behshad (Author) ; Ataie-Ashtiani, Behzad (Supervisor) ; Jamali, Mirmosaddegh (Co-Advisor)
    Existing closed form solutions of contaminant transport problems are limited by the mathematically convenient assumption of uniform flow. These solutions cannot be applied for coastal aquifers where seawater intrusion induces a variable velocity field. The Fourier series method is adapted to obtain a semi-analytical solution for contaminant transport in confined coastal aquifer in which the saltwater wedge is in equilibrium with a freshwater discharge flow. The developed method can be applied for different scenarios of contamination. Two scenarios dealing with, respectively, contaminant leakage from a source at the aquifer top surface and aquifer contamination from the landward boundary are... 

    Development of a Suitable Computational Conjugate Heat Transfer Algorithm to Analyze Turbine Blade Internal Cooling

    , M.Sc. Thesis Sharif University of Technology Sajadi, Ali (Author) ; Darbandi, Masoud (Supervisor)
    Nowadays, the study of flow and heat transfer in turbine engines has become critical due to their increasing use and importance in various engineering industries. The critical issue of blade burning in the first row of turbine’s blades illuminates the critical roles of numerical and experimental activities in reducing these undesirable effects. Since blade cooling is directly related to the secondary air system, one important issue in blade burning research is to utilize the conjugate heat transfer approach. As Known, an increase of about 1% in the mass flow of air entering into the secondary air system would cause an increase of about 0.5% in the engine specific fuel consumption (SFC),... 

    Re-interpreting simultaneous buckling modes of axially compressed isotropic conical shells

    , Article Thin-Walled Structures ; Vol. 84 , November , 2014 , pp. 360-368 ; ISSN: 02638231 Shakouri, M ; Spagnoli, A ; Kouchakzadeh, M. A ; Sharif University of Technology
    Elastic stability of shell structures under certain loading conditions is characterized by a dramatically unstable postbuckling behavior. The presence of simultaneous 'competing' buckling modes (corresponding to the same critical buckling load) is understood to be largely responsible for such behavior. In this paper, within the framework of linear bifurcation eigenvalue analysis and Donnell shallow shell theory, the presence of simultaneous buckling modes in axially compressed isotropic cones is determined using the semi-analytical method of Galerkin. The results are presented in the plane of the dimensionless reciprocal meridional and circumferential buckling half wavelengths, and are... 

    A new simplified formula in prediction of the resonance velocity for multiple masses traversing a thin beam

    , Article Scientia Iranica ; Volume 23, Issue 1 , 2016 , Pages 133-141 ; 10263098 (ISSN) Afghani Khoraskani, R ; Mofid, M ; Eftekhar Azam, S ; Ebrahimzadeh Hassanabadi, M ; Sharif University of Technology
    In this article, transverse vibration of an Euler-Bernoulli beam carrying a series of traveling masses is analyzed. A semi-analytical approach based on eigenfunction expansion method is employed to achieve the dynamic response of the beam. The inertia of the traveling masses changes the fundamental period of the base beam. Therefore, a comprehensive parametric survey is required to reveal the resonance velocity of the traversing inertial loads. In order to facilitate resonance detection for engineering practitioners, a new simplified formula is proposed to approximate the resonance velocity