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  • Open Access


    A Geometric Deformation Constrained Level Set Method for Structural Shape and Topology Optimization

    S.Y. Wang1,2, K.M. Lim2,3, B.C. Khoo2,3, M.Y. Wang4

    CMES-Computer Modeling in Engineering & Sciences, Vol.18, No.3, pp. 155-182, 2007, DOI:10.3970/cmes.2007.018.155

    Abstract In this paper, a geometric deformation constrained level set method is presented as an effective approach for structural shape and topology optimization. A level set method is used to capture the motion of the free boundary of a structure. Furthermore, the geometric deformation of the free boundary is constrained to preserve the structural connectivity and/or topology during the level set evolution. An image-processing-based structural connectivity and topology preserving approach is proposed. A connected components labeling technique based on the 4-neighborhood connectivity measure and a binary image is used for the present region identification. The corresponding binary image after an exploratory… More >

  • Open Access


    Structural Arrangement Effects of Mineral Platelets on the Nature of Stress Distribution in Bio-Composites

    S. Anup1, S. M. Sivakumar2, G. K. Suraishkumar3

    CMES-Computer Modeling in Engineering & Sciences, Vol.18, No.2, pp. 145-154, 2007, DOI:10.3970/cmes.2007.018.145

    Abstract Bone is a hierarchical bio-composite, and has a staggered arrangement of soft protein molecules interspaced with hard mineral platelets at the fine ultrastructure level. The investigation into reasons for high fracture toughness of bio-composites such as bone requires consideration of properties at the different levels of hierarchy. In this work, the analysis is done at the continuum level, but the properties used are appropriate to that of the level considered. In this way, the properties at the fine ultrastructure level of bone is considered in the stress distribution analysis of a platelet adjacent to the broken platelet. Results show the… More >

  • Open Access


    Buckling and Free Vibrations of Sandwich General shells of Revolution with Composite facings and Viscoelastic core under Thermal Environment using Semi-analytical Method

    Sharnappa1, N. Ganesan2, Raju Sethuraman3

    CMES-Computer Modeling in Engineering & Sciences, Vol.18, No.2, pp. 121-144, 2007, DOI:10.3970/cmes.2007.018.121

    Abstract This article presents the study on buckling and free vibration behavior of sandwich general shells of revolution under thermal environment using Wilkins theory. The temperature assumes to be uniform over the shell structure. The numerical analysis is based on the semi-analytical finite element method applicable to thick shells. The analysis is carried out for different geometry such as truncated conical and hemispherical shells with various facing and core materials under clamped-clamped boundary condition. The parametric study is carried out for different core to facing (tc / tf) thickness ratio by considering the temperature dependent and independent material properties of the… More >

  • Open Access


    Finite Element Analysis of Particle Assembly-water Coupled Frictional Contact Problem

    S. Ozaki1, K. Hashiguchi2, T. Okayasu2, D.H. Chen1

    CMES-Computer Modeling in Engineering & Sciences, Vol.18, No.2, pp. 101-120, 2007, DOI:10.3970/cmes.2007.018.101

    Abstract In order to analyze precisely not only the elastoplastic deformation phenomenon of saturated particle assembly such as soils, grains, powdered and tablet medicines or three dimensional cellular materials, but also the frictional sliding phenomenon between saturated particle assembly and other bodies, a particle assembly-water coupled finite element program, that incorporates both the subloading surface and the subloading-friction models, is developed. Subsequently, simulations of the compaction behavior of saturated particle assembly under strain rate control are performed. It is revealed by the numerical experiment adopting the finite element program that the frictional sliding behavior of the contact boundary influences both the… More >

  • Open Access


    Numerical Simulations of Irregular Particle Transport in Turbulent Flows Using Coupled LBM-DEM

    K. Han 1, Y. T. Feng 1, D. R. J. Owen1

    CMES-Computer Modeling in Engineering & Sciences, Vol.18, No.2, pp. 87-100, 2007, DOI:10.3970/cmes.2007.018.087

    Abstract Numerical procedures are introduced for simulations of irregular particle transport in turbulent flows using the coupled lattice Boltzmann method (LBM) and the discrete element method (DEM). The fluid field is solved by the extended LBM with the incorporation of the Smagorinsky turbulence approach, while particle interaction is modeled by the DEM. The hydrodynamic interactions between fluid and particles are realised through an immersed boundary condition, which gives rise to a coupled solution strategy to model the fluid-particle system under consideration. Main computational aspects comprise the lattice Boltzmann formulation for the solution of fluid flows; the incorporation of the large eddy… More >

  • Open Access


    A Hybrid Laplace Transform/Finite Difference Boundary Element Method for Diffusion Problems

    A. J. Davies1, D. Crann1, S. J. Kane1, C-H. Lai2

    CMES-Computer Modeling in Engineering & Sciences, Vol.18, No.2, pp. 79-86, 2007, DOI:10.3970/cmes.2007.018.079

    Abstract The solution process for diffusion problems usually involves the time development separately from the space solution. A finite difference algorithm in time requires a sequential time development in which all previous values must be determined prior to the current value. The Stehfest Laplace transform algorithm, however, allows time solutions without the knowledge of prior values. It is of interest to be able to develop a time-domain decomposition suitable for implementation in a parallel environment. One such possibility is to use the Laplace transform to develop coarse-grained solutions which act as the initial values for a set of fine-grained solutions. The… More >

  • Open Access


    Computation of transient viscous flows using indirect radial basis function networks

    N. Mai-Duy1, L. Mai-Cao2, T. Tran-Cong3

    CMES-Computer Modeling in Engineering & Sciences, Vol.18, No.1, pp. 59-78, 2007, DOI:10.3970/cmes.2007.018.059

    Abstract In this paper, an indirect/integrated radial-basis-function network (IRBFN) method is further developed to solve transient partial differential equations (PDEs) governing fluid flow problems. Spatial derivatives are discretized using one- and two-dimensional IRBFN interpolation schemes, whereas temporal derivatives are approximated using a method of lines and a finite-difference technique. In the case of moving interface problems, the IRBFN method is combined with the level set method to capture the evolution of the interface. The accuracy of the method is investigated by considering several benchmark test problems, including the classical lid-driven cavity flow. Very accurate results are achieved using relatively low numbers… More >

  • Open Access


    A Geometrical Comparison between Cell Method and Finite Element Method in Electrostatics

    M. Heshmatzadeh, G. E. Bridges1

    CMES-Computer Modeling in Engineering & Sciences, Vol.18, No.1, pp. 45-58, 2007, DOI:10.3970/cmes.2007.018.045

    Abstract Cell Method, a Finite Formulation technique, is compared in detail with the Finite Element Method (FEM), a differential-based numerical technique. In the finite formulation technique, Poisson's equation is described starting from a topological foundation. The final set of algebraic equations resulting from the two approaches are compared in matrix form. The equivalence of the coefficient matrices is proven for a Voronoi dual mesh and linear shape functions in the FEM. The difference between the source (charge) vectors in the two approaches is described. It is shown that the use of linear shape functions in the FEM is equivalent to the… More >

  • Open Access


    Thermo-Poro-Elastostatic Green's Functions for Unsaturated Soils

    Ehsan Jabbari1, Behrouz Gatmiri2,3

    CMES-Computer Modeling in Engineering & Sciences, Vol.18, No.1, pp. 31-44, 2007, DOI:10.3970/cmes.2007.018.031

    Abstract In this paper after a discussion about the evolution of the unsaturated soils' governing differential equations and a brief history of the Green's functions for porous media, the governing equations, i.e., the mathematical model in the presence of heat effects are presented and simplified so as the derivation of the associated Green's functions be in the realm of possibility. The thermal two- and three-dimensional, full- and half-space Green's functions for unsaturated porous media, although in a relatively simplified form, are being introduced for the first time, following the previous works of the authors. The derived Green's functions have been demonstrated… More >

  • Open Access


    Design Optimization of the Intake of a Small-Scale Turbojet Engine

    R. Amirante1, L.A. Catalano2, A. Dadone1, V.S.E. Daloiso1

    CMES-Computer Modeling in Engineering & Sciences, Vol.18, No.1, pp. 17-30, 2007, DOI:10.3970/cmes.2007.018.017

    Abstract This paper proposes a gradient-based progressive optimization technique, which can be efficiently combined with black-box simulation codes. Its efficiency relies on the simultaneous convergence of the flow solution, of the gradient evaluation, and of the design update, as well as on the use of progressively finer grids. The developed numerical technique has general validity and is here applied to the fluid-dynamic design optimization of the intake of a small-size turbojet engine, at high load and zero flight speed. Two simplified design criteria are proposed, which avoid simulating the flow in any turbojet components other than the intake itself. Using a… More >

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