Search for: boundary-integral-equations
0.006 seconds

    Asymmetric wave propagation in a transversely isotropic half-space in displacement potentials

    , Article International Journal of Engineering Science ; Volume 46, Issue 7 , 2008 , Pages 690-710 ; 00207225 (ISSN) Khojasteh, A ; Rahimian, M ; Eskandari, M ; Pak, R. Y. S ; Sharif University of Technology
    With the aid of a complete representation using two displacement potentials, an efficient and accurate analytical derivation of the fundamental Green's functions for a transversely isotropic elastic half-space subjected to an arbitrary, time-harmonic, finite, buried source is presented. The formulation includes a complete set of transformed stress-potential and displacement-potential relations that can be useful in a variety of elastodynamic as well as elastostatic problems. The present solutions are analytically in exact agreement with the existing solutions for a half-space with isotropic material properties. For the numerical evaluation of the inversion integrals, a quadrature scheme... 

    Boundary integral equation analysis of an inhomogeneous medium made of functionally graded materials

    , Article Advanced Materials Research ; Volume 685 , 2013 , Pages 285-289 ; 10226680 (ISSN) ; 9783037856765 (ISBN) Ashrafi, H ; Bahadori, M. R ; Keshmiri, H ; Shariyat, M ; Sharif University of Technology
    The present work develops direct graded boundary integral equation formulation for behavior investigation of the inhomogeneous media made of functionally graded materials. The isoparametric boundary elements, the elastostatic governing equations and a weighted residual technique are implemented with the material characteristics that vary continuously along a given dimension. The resulting algorithm is capable of solving the quasistatic problems for elastic functionally graded media with a variety of the boundary conditions and loadings. The inhomogeneous media is made of a ceramic-metal mixture, in which the material properties vary continuously according to a power law graded distribution... 

    A boundary element method for investigation of sloshing in complex 3D containers

    , Article 48th AIAA/ASME/ASCE/AHS/ASC Structures, Structural Dynamics, and Materials Conference, Waikiki, HI, 23 April 2007 through 26 April 2007 ; Volume 8 , 2007 , Pages 8288-8292 ; 02734508 (ISSN); 1563478927 (ISBN); 9781563478925 (ISBN) Firouz Abadi, R. D ; Haddadpour, H ; Ghasemi, M ; Sharif University of Technology
    This paper presents a matrix form model for determination of sloshing frequencies and modes in 3D liquid tanks. The governing equations of the incompressible inviscid potential flow are used to derive the governing boundary integral equation and then the boundary element method along with the collocation method is applied to obtain a matrix form standard eigenvalue problem. The sloshing mass and stiffness matrices are computed using analytical formulas which are given for quadratic boundary elements. Two typical examples are used to validate the introduced model and very good results are achieved in comparison with the exact results in the literature  

    Numerical investigation of flow pattern and hydrodynamic forces of submerged marine propellers using unsteady boundary element method

    , Article Proceedings of the Institution of Mechanical Engineers Part M: Journal of Engineering for the Maritime Environment ; Volume 233, Issue 1 , 2019 , Pages 67-79 ; 14750902 (ISSN) Najafi, S ; Abbaspoor, M ; Sharif University of Technology
    SAGE Publications Ltd  2019
    In this study, a numerical model of unsteady potential flow around submerged marine propellers has been developed. The boundary element approach in combination with time stepping method to model free wake dynamics has been implemented. An important feature of this method in the simulation of pressure-dominant problems is a proper balance between time and accuracy in the numerical process. Another advantage of time stepping method is that there is no need to define wake geometry before modeling. Due to inherent instability of boundary integral equations, a smoothing function to damp the effect of singularities is imposed to the solution. The main innovative idea of this work is that the... 

    Energy transfer in a liquid filled elemental passage of a porous medium for permeability enhancement due to pulsations of a vapor bubble

    , Article Mechanika ; Volume 22, Issue 1 , 2016 , Pages 25-30 ; 13921207 (ISSN) Rambarzin, F ; Shervani Tabar, M. T ; Taeibi Rahni, M ; Tabatabaei Nejad, S. A ; Sharif University of Technology
    Kauno Technologijos Universitetas  2016
    In this paper, a novel method which has been proposed during the last decade for increasing of the permeability of porous media of petroleum reservoirs by transferring of energy via ultrasound waves is investigated numerically. Increasing of permeability of porous media of petroleum reservoirs results in enhancing of oil recovery. This technique is based on the idea of transferring of energy to the liquid filled porous media via the ultrasound waves and consequently producing of pulsating vapor bubbles. The generated vapor bubbles transfer the energy of ultrasound waves in the liquid filled passages of a porous medium through velocity and pressure fields in the liquid domain and in turn... 

    Continuous-time state-space unsteady aerodynamic modeling based on boundary element method

    , Article Engineering Analysis with Boundary Elements ; Volume 36, Issue 5 , 2012 , Pages 789-798 ; 09557997 (ISSN) Mohammadi Amin, M ; Ghadiri, B ; Abdalla, M. M ; Haddadpour, H ; De Breuker, R ; Sharif University of Technology
    In this paper a continuous-time state-space aerodynamic model is developed based on the boundary element method. Boundary integral equations governing the unsteady potential flow around lifting bodies are presented and modified for thin wing configurations. Next, the BEM discretized problem of unsteady flow around flat wing equivalent to the original geometry is recast into the standard form of a continuous-time state-space model considering some auxiliary assumptions. The system inputs are time derivative of the instantaneous effective angle of attack and thickness/camber correction terms while the outputs are unsteady aerodynamic coefficients. To validate the model, its predictions for... 

    Two-dimensional modeling of functionally graded viscoelastic materials using a boundary element approach

    , Article Advanced Materials Research, 7 January 2012 through 8 January 2012 ; Volume 463-464 , January , 2012 , Pages 570-574 ; 10226680 (ISSN) ; 9783037853634 (ISBN) Ashrafi, H ; Bahadori, M. R ; Shariyat, M ; Sharif University of Technology
    In this paper, a 2D boundary element approach able to model viscoelastic functionally graded materials (FGM) is presented. A numerical implementation of the Somigliana identity for displacements is developed to solve 2D problems of exponentially graded elasticity. An FGM is an advanced material in which its composition changes gradually resulting in a corresponding change in properties of the material. The FGM concept can be applied to various materials for structural and functional uses. Our model needs only the Green's function of nonhomogeneous elastostatic problems with material properties that vary continuously along a given dimension. We consider the material properties to be an... 

    A 3D BEM model for liquid sloshing in baffled tanks

    , Article International Journal for Numerical Methods in Engineering ; Volume 76, Issue 9 , June , 2008 , Pages 1419-1433 ; 00295981 (ISSN) Dehghani Firouz Abadi, R ; Haddadpour, H ; Noorain, M. A ; Ghasemi, M ; Sharif University of Technology
    The present work aims at developing a boundary element method to determine the natural frequencies and mode shapes of liquid sloshing in 3D baffled tanks with arbitrary geometries. Green's theorem is used with the governing equation of potential flow and the walls and free surface boundary conditions are applied. A zoning method is introduced to model arbitrary arrangements of baffles. By discretizing the flow boundaries to quadrilateral elements, the boundary integral equation is formulated into a general matrix eigenvalue problem. The governing equations are then reduced to a more efficient form that is merely represented in terms of the potential values of the free surface nodes, which...