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S Valliappan - One of the best experts on this subject based on the ideXlab platform.

  • wave propagation analysis of two phase saturated porous media using coupled finite Infinite Element method
    Soil Dynamics and Earthquake Engineering, 1999
    Co-Authors: Nasser Khalili, M. Yazdchi, S Valliappan
    Abstract:

    Abstract A fully coupled two-dimensional Infinite Element for frequency domain analysis of wave propagation problems in unbounded saturated porous media is presented. The decay function of the Element is derived based on the analytical solution of Biot (Theory of propagation of elastic waves in fluid-saturated porous solid. 1. Low-frequency range. Journal of the Acoustical Society of America 1956;28(2):168–78) formulation for a one-dimensional configuration. After a detailed description of the Element formulation, the effectiveness and the accuracy of the present Infinite Element in simulating unbounded domains are demonstrated through two numerical examples. Extremely good agreements are obtained between the results from a very large mesh and those from the coupled finite–Infinite Element method. It is shown that the accuracy of the solutions deteriorate significantly when the Infinite Elements are removed and fixed to free displacement boundary conditions are introduced at the truncated boundaries.

  • An axi‐symmetric Infinite Element for transient radial flow problems
    International Journal for Numerical and Analytical Methods in Geomechanics, 1999
    Co-Authors: Nasser Khalili, S Valliappan, M. Yazdchi
    Abstract:

    The formulation of an axi-symmetric Infinite Element for transient analysis of flow problems in unbounded domain is presented. The theoretical basis as well as the implementation of the Element is discussed, and the Element decay function is derived using the analytical solution of a one-dimensional axially symmetric configuration. The form of decay within the Element is described as a function of both time and space, and thus the hydraulic head distribution in the far field is simulated rigorously. The accuracy and the efficiency of the proposed Element are demonstrated through several numerical examples in Infinite media. In general, it is shown that using the present Infinite Element transient flow problems in unbounded domains can be simulated effectively. Copyright © 1999 John Wiley & Sons, Ltd.

  • Wave propagation analysis of two-phase saturated porous media using coupled finite–Infinite Element method
    Soil Dynamics and Earthquake Engineering, 1999
    Co-Authors: Nasser Khalili, M. Yazdchi, S Valliappan
    Abstract:

    Abstract A fully coupled two-dimensional Infinite Element for frequency domain analysis of wave propagation problems in unbounded saturated porous media is presented. The decay function of the Element is derived based on the analytical solution of Biot (Theory of propagation of elastic waves in fluid-saturated porous solid. 1. Low-frequency range. Journal of the Acoustical Society of America 1956;28(2):168–78) formulation for a one-dimensional configuration. After a detailed description of the Element formulation, the effectiveness and the accuracy of the present Infinite Element in simulating unbounded domains are demonstrated through two numerical examples. Extremely good agreements are obtained between the results from a very large mesh and those from the coupled finite–Infinite Element method. It is shown that the accuracy of the solutions deteriorate significantly when the Infinite Elements are removed and fixed to free displacement boundary conditions are introduced at the truncated boundaries.

  • 1D Infinite Element for dynamic problems in saturated porous media
    Communications in Numerical Methods in Engineering, 1997
    Co-Authors: Nasser Khalili, S Valliappan, J. Tabatabaee Yazdi, M. Yazdchi
    Abstract:

    A fully coupled 1D Infinite Element for frequency domain analysis of wave propagation problems in unbounded saturated porous media is presented. The Element wave propagation function is derived using an analytical solution for Biot's formulation (1962). The effectiveness and the accuracy of the Infinite Element proposed are demonstrated through a simple wave propagation problem in a semi-Infinite soil column subjected to a harmonic surface loading. It is shown that an accurate representation of the problem can be obtained by coupling the conventional finite Elements with the proposed Infinite Element. The accuracy of the solution significantly deteriorates when free or fixed boundary conditions are imposed at the truncated boundary instead of the Infinite Element. © 1997 John Wiley & Sons, Ltd.

  • a dynamic Infinite Element for three dimensional Infinite domain wave problems
    International Journal for Numerical Methods in Engineering, 1993
    Co-Authors: Chongbin Zhao, S Valliappan
    Abstract:

    A three-dimensional dynamic Infinite Element which satisfies the following requirements: (1) displacement compatibility on the interface between finite and Infinite Elements; (2) definition of the wave propagation and amplitude attenuation behaviours in the Infinite Element using wave propagation functions; (3) convergence of the generalized integrals related to mass and stiffness matrices of the Infinite Element; and (4) displacement continuity along the common boundary of neighbouring Infinite Elements in the case of simulating multiple material layers or multiple wave numbers within the foundation, is presented in this paper

David S. Burnett - One of the best experts on this subject based on the ideXlab platform.

  • An ellipsoidal acoustic Infinite Element
    Computer Methods in Applied Mechanics and Engineering, 1998
    Co-Authors: David S. Burnett, Richard Lovell Holford
    Abstract:

    Abstract In previous papers the authors presented new 3-D time-harmonic prolate and oblate spheroidal acoustic Infinite Elements, based on new prolate and oblate spheroidal multipole expansions, for modeling acoustic fields in unbounded domains. Here, we present the development of an ellipsoidal Infinite Element, which is the logical generalization of those Elements. This development is also based on a new multipole expansion as well as a new system of ellipsoidal coordinates. The Element stiffness, radiation-damping and mass matrices are developed and presented in sufficient detail to enable their software implementation. Both the new coordinate system and the new Element include the previous spheroidal coordinate systems and spheroidal Elements as limiting cases. Therefore, all the previously reported performance data for the spheroidal Elements apply to this ellipsoidal Element when used in spheroidal form. Since the three axes of an ellipsoid can be chosen independently, an ellipsoid can circumscribe any structural shape at least as closely, and generally more closely, than a prolate or oblate spheroid. The resulting reduction in size of the finite computational domain will result in even greater computational speeds than those already reported for the spheroidal Elements. The Element may be used to model problems in free-space (4π steradians), half-space (2π), quarter-space (π) or eighth-space ( π 2 ). Since this Infinite Element provides maximum computational efficiency for structures of all shapes, software Element libraries would need only this one Element for all problems in unbounded domains.

  • a three dimensional acoustic Infinite Element based on a prolate spheroidal multipole expansion
    Journal of the Acoustical Society of America, 1994
    Co-Authors: David S. Burnett
    Abstract:

    This paper describes a new three‐dimensional (3‐D) time‐harmonic acoustic Infinite Element for modeling acoustic fields in exterior domains, typically surrounding a structure. This ‘‘prolate spheroidal Infinite Element’’ is based on a new multipole expansion that is the exact solution for arbitrary scattered and/or radiated fields exterior to a prolate spheroid of any eccentricity. A combination of both prolate and oblate spheroidal Infinite Elements (the latter to be published separately) provides a capability for very efficiently modeling acoustic fields surrounding structures of virtually any practical shape. This new prolate Element has symmetric matrices that are as cheap to generate as for 2‐D Elements because only 2‐D integrals need to be numerically evaluated. The prolate Element (along with a symmetric‐matrix fluid–structure coupling Element, also to be published separately) fits naturally into purely structural finite Element codes, thereby providing a structural acoustics capability. For the cl...

  • A three‐dimensional acoustic Infinite Element based on a prolate spheroidal multipole expansion
    The Journal of the Acoustical Society of America, 1994
    Co-Authors: David S. Burnett
    Abstract:

    This paper describes a new three‐dimensional (3‐D) time‐harmonic acoustic Infinite Element for modeling acoustic fields in exterior domains, typically surrounding a structure. This ‘‘prolate spheroidal Infinite Element’’ is based on a new multipole expansion that is the exact solution for arbitrary scattered and/or radiated fields exterior to a prolate spheroid of any eccentricity. A combination of both prolate and oblate spheroidal Infinite Elements (the latter to be published separately) provides a capability for very efficiently modeling acoustic fields surrounding structures of virtually any practical shape. This new prolate Element has symmetric matrices that are as cheap to generate as for 2‐D Elements because only 2‐D integrals need to be numerically evaluated. The prolate Element (along with a symmetric‐matrix fluid–structure coupling Element, also to be published separately) fits naturally into purely structural finite Element codes, thereby providing a structural acoustics capability. For the cl...

  • Structural acoustic modeling using a new high accuracy acoustic Infinite Element
    The Journal of the Acoustical Society of America, 1993
    Co-Authors: David S. Burnett
    Abstract:

    This new 3‐D time‐harmonic acoustic Infinite Element uses a truncated form of the exact asymptotic series solution for general scattered and/or radiated fields, providing an accurate approximation all the way to infinity. The Infinite Element and a companion fluid–structure coupling Element have symmetric matrices that fit seamlessly into any structural finite Element code, providing a structural acoustic capability as versatile and powerful as the structural code itself. Most important, this approach is several orders of magnitude faster, for the same accuracy, than the traditional and almost universally used boundary Element method (BEM) for the acoustics, i.e., the surface Helmholtz integral equation, which the author also developed and used for several years. The reason is that the bandwidth of the coupled system equations is much smaller for Infinite Elements (being a domain method) than for the BEM. Experience with both methods has revealed that the severe computational inefficiency of the BEM limit...

Youqing Wang - One of the best experts on this subject based on the ideXlab platform.

  • Equivalent dynamic Infinite Element for soil-structure interaction
    Finite Elements in Analysis and Design, 2013
    Co-Authors: Youqing Wang
    Abstract:

    In this paper, equivalent dynamic Infinite Element is proposed. The idea of the method is based on the elastic recovery of general Infinite Element and the energy absorption of viscous boundary. The equivalent dynamic Infinite Element is not required for wave functions, since the waves on the interfaces with adjacent finite and Infinite Elements are absorbed by the equivalent damping. And the role of the far field medium in the elastic recovery has also been considered in the equivalent dynamic Element. Such an Element can be used directly as general finite Element and appropriates for dynamic soil-structure interaction problems. Numerical analyses involving comparisons with known analytical or numerical solutions are presented. The results obtained show the effectiveness of the proposed equivalent dynamic Infinite Element.

Steffen Marburg - One of the best experts on this subject based on the ideXlab platform.

  • Spectral Stochastic Infinite Element Method in Vibroacoustics
    Journal of Theoretical and Computational Acoustics, 2020
    Co-Authors: Felix Kronowetter, Lennart Moheit, Martin Eser, Kian K. Sepahvand, Steffen Marburg
    Abstract:

    A novel method to solve exterior Helmholtz problems in the case of multipole excitation and random input data is developed. The Infinite Element method is applied to compute the sound pressure field in the exterior fluid domain. The consideration of random input data leads to a stochastic Infinite Element formulation. The generalized polynomial chaos expansion of the random data results in the spectral stochastic Infinite Element method. As a solution technique, the non-intrusive collocation method is chosen. The performance of the spectral stochastic Infinite Element method is demonstrated for a time-harmonic problem and an eigenfrequency study.

  • Spectral Stochastic Infinite Element Method in Vibroacoustics
    2020
    Co-Authors: Felix Kronowetter, Lennart Moheit, Martin Eser, Kian K. Sepahvand, Steffen Marburg
    Abstract:

    A novel method to solve exterior Helmholtz problems in the case of multipole excitation and random input data is developed. The Infinite Element method is applied to compute the sound pressure fiel...

Frédéric Magoulès - One of the best experts on this subject based on the ideXlab platform.

  • Analysis of a conjugated Infinite Element method for acoustic scattering
    Computers & Structures, 2007
    Co-Authors: Jean-christophe Autrique, Frédéric Magoulès
    Abstract:

    This work is devoted to a study of a conjugated Infinite Element method for Helmholtz problems in exterior domains. A formulation of this method with Lagrange multipliers defined on (semi-)Infinite space is presented and analyzed in a domain decomposition context. The implementation aspects of this method in a parallel industrial acoustic software (SYSNOISE) are described in details. Numerical results show the computational efficiency of this method on acoustic scattering problems.

  • Studies of an Infinite Element method for acoustical radiation
    Applied Mathematical Modelling, 2006
    Co-Authors: Jean-christophe Autrique, Frédéric Magoulès
    Abstract:

    Infinite Element computations are very efficient for predicting the vibro-acoustic response and sensitivities of a vibrating structure for an exterior acoustic domain. In addition, domain decomposition methods are very powerful algorithms for solving large linear systems in parallel. In this paper, an Infinite Element method is proposed and analyzed for parallel computations purpose. An original formulation of this method with Lagrange multipliers defined on (semi-)Infinite space is presented. The implementation aspects of this method in an industrial acoustic software (SYSNOISE) are discussed. New numerical results illustrate the efficiency of the proposed method for realistic acoustical radiation problems.

  • NUMERICAL ANALYSIS OF A COUPLED FINITE-Infinite Element METHOD FOR EXTERIOR HELMHOLTZ PROBLEMS
    Journal of Computational Acoustics, 2006
    Co-Authors: Jean-christophe Autrique, Frédéric Magoulès
    Abstract:

    Coupled finite-Infinite Element computations are very efficient for modeling large scale acoustics problems. Parallel algorithms, like sub-structuring and domain decomposition methods, have shown to be very efficient for solving huge linear systems arising from acoustics. In this paper, a coupled finite-Infinite Element method is described, formulated and analyzed for parallel computations purpose. New numerical results illustrate the efficiency of this method for academic test cases and industrial problems alike.