• Title/Summary/Keyword: Discrete-Element-Method

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Predicted Air Flow Around Objects Using the Discrete Vortex Method

  • Kim, Tae-Hyeung
    • Journal of Korean Society for Atmospheric Environment
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    • v.9 no.E
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    • pp.347-357
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    • 1993
  • The Lagrangian grid-free numerical method, the discrete vortex method, was applied to solve the Navier-Stokes euqations. This method avoids the introduction of numerical viscosity swamping the real physical viscosity at high Reynolds number, unlike Eulerian method, e.g. finite difference and element methods. The boundary integral equation method for the potential flow solution was included to make the discrete vortex method more feasible for complex geometries. The fast adaptive multipole expansion method was incorporated to reduce the computational time from $O(N^2)$ to O(N) for the computations of vortex-vortex interactions. The test problems were air flow around one circular cylinder and two circular cylinders in tandem with various gaps. The numerical results were in excellent gareement with the experimental and other computational results. The applicabilty of the method was discussed with the indoor and the outdoor air pollution problems, especially the contaminant transport in the recirculation regions.

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Updating of Finite Element Model and Joint Identification with Frequency Response Function (주파수응답함수를 이용한 유한요소모델의 개선 및 결합부 동정)

  • 서상훈;지태한;박영필
    • Journal of KSNVE
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    • v.7 no.1
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    • pp.61-69
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    • 1997
  • Despite of the development in the finite element method, it is difficult to get the finite element model describing the dynamic characteristics of the complex structure exactly. Therefore a number of different methods have been developed in order to update the finite element model of a structure using vibration test data. This paper outlines the basic formulation for the frequency response function based updating method. One important advantage of this method is that the intermediate step of performing an eigensolution extraction is unnecessary. Using simulated experimental data, studies are conducted in the case of 10 DOF discrete system. The solution of noisy and incomplete experimental data is discussed. True measured frequency response function data are used for updating the finite element model of a beam and a plate. Its applicability to the joint identification is also considered.

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An hp-angular adaptivity with the discrete ordinates method for Boltzmann transport equation

  • Ni Dai;Bin Zhang;Xinyu Wang;Daogang Lu;Yixue Chen
    • Nuclear Engineering and Technology
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    • v.55 no.2
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    • pp.769-779
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    • 2023
  • This paper describes an hp-angular adaptivity algorithm in the discrete ordinates method for Boltzmann transport applications with strong angular effects. This adaptivity uses discontinuous finite element quadrature sets with different degrees, which updates both angular mesh and the degree of the underlying discontinuous finite element basis functions, allowing different angular local refinement to be applied in space. The regular and goal-based error metrics are considered in this algorithm to locate some regions to be refined. A mapping algorithm derived by moment conservation is developed to pass the angular solution between spatial regions with different quadrature sets. The proposed method is applied to some test problems that demonstrate the ability of this hp-angular adaptivity to resolve complex fluxes with relatively few angular unknowns. Results illustrate that a reduction to approximately 1/50 in quadrature ordinates for a given accuracy compared with uniform angular discretization. This method therefore offers a highly efficient angular adaptivity for investigating difficult particle transport problems.

ERROR ESTIMATES FOR FULLY DISCRETE DISCONTINUOUS GALERKIN METHOD FOR NONLINEAR PARABOLIC EQUATIONS

  • Ohm, Mi-Ray;Lee, Hyun-Yong;Shin, Jun-Yong
    • Journal of applied mathematics & informatics
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    • v.28 no.3_4
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    • pp.953-966
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    • 2010
  • In this paper, we develop discontinuous Galerkin methods with penalty terms, namaly symmetric interior penalty Galerkin methods to solve nonlinear parabolic equations. By introducing an appropriate projection of u onto finite element spaces, we prove the optimal convergence of the fully discrete discontinuous Galerkin approximations in ${\ell}^2(L^2)$ normed space.

Analysis of a strip footing on a homogenous soil using element free Galerkin method

  • Ganaiea, Aashiq H.;Sawant, Vishwas A.
    • Coupled systems mechanics
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    • v.4 no.4
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    • pp.365-383
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    • 2015
  • Strip footing is an important type of shallow foundations and is commonly used beneath the walls. Analysis of shallow foundation involves the determination of stresses and deformations. Element free Galerkin method, one of the important mesh free methods, is used for the determination of stresses and deformations. Element free Galerkin method is an efficient and accurate method as compared to finite element method. The Element Free Galerkin method uses only a set of nodes and a description of model boundary is required to generate the discrete equation. Strip footing of width 2 m subjected to a loading intensity of 200 kPa is studied. The results obtained are agreeing with the values obtained using analytical solutions available in the literature. Parametric study is done and the effect of modulus of deformation, Poisson's ratio and scaling parameter on deformation and stresses are determined.

Comparative Numerical Analysis of Homogenized and Discrete-Micromechanics Models for Functionally Graded Materials (기능경사재를 위한 균질화와 이산화-미시역학 모델에 대한 비교 수치해석)

  • Ha, Dae-Yul;Lee, Hong-Woo;Cho, Jin-Rae
    • Proceedings of the KSME Conference
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    • 2000.04a
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    • pp.399-404
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    • 2000
  • Functionally graded materials(FGMs) involve dual-phase graded layers in which two different constituents are mixed continuously and functionally according to a given volume fraction. For the analysis of their thermo-mechanical response, conventional homogenized methods have been widely employed in order to estimate equivalent material properties of the graded layer. However, such overall estimations are insufficient to accurately predict the local behavior. In this paper, we compare the thermo-elastic behaviors predicted by several overall material-property estimation techniques with those obtained by discrete analysis models utilizing the finite element method, for various volume fractions and loading conditions.

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Modeling concrete fracturing using a hybrid finite-discrete element method

  • Elmo, Davide;Mitelman, Amichai
    • Computers and Concrete
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    • v.27 no.4
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    • pp.297-304
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    • 2021
  • The hybrid Finite-Discrete Element (FDEM) approach combines aspects of both finite elements and discrete elements with fracture mechanics principles, and therefore it is well suited for realistic simulation of quasi-brittle materials. Notwithstanding, in the literature its application for the analysis of concrete is rather limited. In this paper, the proprietary FDEM code ELFEN is used to model concrete specimens under uniaxial compression and indirect tension (Brazilian tests) of different sizes. The results show that phenomena such as size effect and influence of strain-rate are captured using this modeling technique. In addition, a preliminary model of a slab subjected to dynamic shear punching due to progressive collapse is presented. The resulting fracturing pattern of the impacted slab is similar to observations from actual collapse.

Numerical analysis of a complex slope instability: Pseudo-wedge failure

  • Babanouri, Nima;Sarfarazi, Vahab
    • Geomechanics and Engineering
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    • v.15 no.1
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    • pp.669-676
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    • 2018
  • The "pseudo-wedge" failure is a name for a complex instability occurring at the Sarcheshmeh open-pit mine (Iran). The pseudo-wedge failure contains both the rock bridge failure and sliding along pre-existing discontinuities. In this paper, a cross section of the failure area was first modeled using a bonded-particle method. The results indicated development of tensile cracks at the slope toe which explains the freedom of pseudo-wedge blocks to slide. Then, a three-dimensional discrete element method was used to perform a block analysis of the instability. The technique of shear strength reduction was used to calculate the factor of safety. Finally, the influence of geometrical characteristics of the mine wall on the pseudo-wedge failure was investigated. The safety factor significantly increases as the dip and dip direction of the wall decrease, and reaches an acceptable value with a 10-degree decrease of them.

NUMERICAL PROPERTIES OF GAUGE METHOD FOR THE INCOMPRESSIBLE NAVIER-STOKES EQUATIONS

  • Pyo, Jae-Hong
    • Journal of the Korean Society for Industrial and Applied Mathematics
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    • v.14 no.1
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    • pp.43-56
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    • 2010
  • The representative numerical algorithms to solve the time dependent Navier-Stokes equations are projection type methods. Lots of projection schemes have been developed to find more accurate solutions. But most of projection methods [4, 11] suffer from inconsistency and requesting unknown datum. E and Liu in [5] constructed the gauge method which splits the velocity $u=a+{\nabla}{\phi}$ to make consistent and to replace requesting of the unknown values to known datum of non-physical variables a and ${\phi}$. The errors are evaluated in [9]. But gauge method is not still obvious to find out suitable combination of discrete finite element spaces and to compute boundary derivative of the gauge variable ${\phi}$. In this paper, we define 4 gauge algorithms via combining both 2 decomposition operators and 2 boundary conditions. And we derive variational derivative on boundary and analyze numerical results of 4 gauge algorithms in various discrete spaces combinations to search right discrete space relation.