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  • Open Access


    Insight into High-quality Aerodynamic Design Spaces through Multi-objective Optimization

    T. Kipouros1, D.M. Jaeggi2, W.N. Dawes3, G.T. Parks2,A.M. Savill1, P.J. Clarkson2

    CMES-Computer Modeling in Engineering & Sciences, Vol.37, No.1, pp. 1-44, 2008, DOI:10.3970/cmes.2008.037.001

    Abstract An approach to support the computational aerodynamic design process is presented and demonstrated through the application of a novel multi-objective variant of the Tabu Search optimization algorithm for continuous problems to the aerodynamic design optimization of turbomachinery blades. The aim is to improve the performance of a specific stage and ultimately of the whole engine. The integrated system developed for this purpose is described. This combines the optimizer with an existing geometry parameterization scheme and a well-established CFD package. The system's performance is illustrated through case studies -- one two-dimensional, one three-dimensional -- in which… More >

  • Open Access


    A Novel Fictitious Time Integration Method for Solving the Discretized Inverse Sturm-Liouville Problems, For Specified Eigenvalues

    Chein-Shan Liu1, Satya N. Atluri2

    CMES-Computer Modeling in Engineering & Sciences, Vol.36, No.3, pp. 261-286, 2008, DOI:10.3970/cmes.2008.036.261

    Abstract The inverse Sturm-Liouville problem finds its applications in the identification of mechanical properties and/or geometrical configurations of a vibrating continuous medium; however, this problem is hard to solve, either theoretically or numerically. Previously, Liu (2008a) has constructed a Lie-group shooting method to determine the eigenvalues, and the corresponding eigenfunctions, for the direct Sturm-Liouville problem. In this study, we are concerned with solving the inverse Sturm-Liouville problem, by developing a Lie-group of SL(2,R) to construct nonlinear algebraic equations (NAEs), when discrete eigenvalues are specified. Our purpose here is to use these NAEs to solve the unknown function More >

  • Open Access


    A Parameter Free Cost Function for Multi-Point Low Speed Airfoil Design

    G. Veble1,2,3

    CMES-Computer Modeling in Engineering & Sciences, Vol.36, No.3, pp. 243-260, 2008, DOI:10.3970/cmes.2008.036.243

    Abstract A simple cost function is proposed that depends on the inviscid pressure distribution around an airfoil and that, when minimized, results in airfoils that promote laminar flow. Additional constraints specify the design point of the airfoil. The method allows for straightforward inclusion of multiple design points. The resulting airfoils are quantitatively similar to those already successfully used in practice. More >

  • Open Access


    Methods to Automatically Build Point Distribution Models for Objects like Hand Palms and Faces Represented in Images

    Maria João M. Vasconcelos1, João Manuel R. S. Tavares1

    CMES-Computer Modeling in Engineering & Sciences, Vol.36, No.3, pp. 213-242, 2008, DOI:10.3970/cmes.2008.036.213

    Abstract In this work we developed methods to automatically extract significant points of objects like hand palms and faces represented in images that can be used to build Point Distribution Models automatically. These models are further used to segment the modelled objects in new images, through the use of Active Shape Models or Active Appearance Models. These models showed to be efficient in the segmentation of objects, but had as drawback the fact that the labelling of the landmark points was usually manually made and consequently time consuming. Thus, in this paper we describe some methods More >

  • Open Access


    Probabilistic Collocation used in a Two-Step approach for \\efficient uncertainty quantification in computational fluid dynamics.

    G.J.A. Loeven1,2, H. Bijl3

    CMES-Computer Modeling in Engineering & Sciences, Vol.36, No.3, pp. 193-212, 2008, DOI:10.3970/cmes.2008.036.193

    Abstract In this paper a Two-Step approach is presented for uncertainty quantification for expensive problems with multiple uncertain parameters. Both steps are performed using the Probabilistic Collocation method. The first step consists of a sensitivity analysis to identify the most important parameters of the problem. The sensitivity derivatives are obtained using a first or second order Probabilistic Collocation approximation. For the most important parameters the probability distribution functions are propagated using the Probabilistic Collocation method using higher order approximations. The Two-Step approach is demonstrated for flow around a NACA0012 airfoil with eight uncertain parameters in the More >

  • Open Access


    Meshless Analysis of Ductile Failure

    L. Li, S. Liu, H. Wang1

    CMES-Computer Modeling in Engineering & Sciences, Vol.36, No.2, pp. 173-192, 2008, DOI:10.3970/cmes.2008.036.173

    Abstract We study ductile fracture using Reproducing Kernel Particle Interpolation and the Gurson-Tvergaard-Needleman (GTN) model. The meshless simulations are compared with the available experimental results and previous finite element simulations for crack propagation. The results agree well with experimental results, and it is confirmed that the proposed method provides a convenient and yet accurate means for simulation of ductile fracture. More >

  • Open Access


    Integral Method for Contact Problem of Bonded Plane Material with Arbitrary Cracks

    Yueting Zhou1, Xing Li2, Dehao Yu1

    CMES-Computer Modeling in Engineering & Sciences, Vol.36, No.2, pp. 147-172, 2008, DOI:10.3970/cmes.2008.036.147

    Abstract A problem for bonded plane material with a set of curvilinear cracks, which is under the action of a rigid punch with the foundation of convex shape, has been considered in this paper. Kolosov-Muskhelishvili complex potentials are constructed as integral representations with the Cauchy kernels with respect to derivatives of displacement discontinuities along the crack contours and pressure under the punch. The contact of crack faces is considered. The considered problem has been transformed to a system of complex Cauchy type singular integral equations of first and second kind. The presented approach allows to consider More >

  • Open Access


    A Local Hypersingular Boundary Integral Equation Method Using a Triangular Background Mesh

    V. Vavourakis 1

    CMES-Computer Modeling in Engineering & Sciences, Vol.36, No.2, pp. 119-146, 2008, DOI:10.3970/cmes.2008.036.119

    Abstract In this paper, a new meshless Local Hypersingular Boundary Integral Equation method is presented for the analysis of two-dimensional elastostatic problems. The elastic domain is discretized by placing arbitrarily nodes on its boundary and interior. Given this set of nodes, the corresponding map of background triangles is constructed through a common triangulation algorithm. The local domain of each node consists of the union of triangles that this point lies, thus, creating a polygonal line of its local boundary. The local boundary integral equations of both displacements and stresses of the conventional Boundary Elements Method are… More >

  • Open Access


    Large Deformation Analysis with Galerkin based Smoothed Particle Hydrodynamics

    S. Wong, Y. Shie

    CMES-Computer Modeling in Engineering & Sciences, Vol.36, No.2, pp. 97-118, 2008, DOI:10.3970/cmes.2008.036.097

    Abstract In this paper, we propose a Galerkin-based smoothed particle hydrodynamics (SPH) formulation with moving least-squares meshless approximation, applied to solid mechanics and large deformation. Our method is truly meshless and based on Lagrangian kernel formulation and stabilized nodal integration. The performance of the methodology proposed is tested through various simulations, demonstrating the attractive ability of particle methods to handle severe distortions and complex phenomena. More >

  • Open Access


    A Node-Based Element for Analysis of Planar Piezoelectric Structures

    H. Nguyen-Van1, N.Mai-Duy1, T. Tran-Cong1

    CMES-Computer Modeling in Engineering & Sciences, Vol.36, No.1, pp. 65-96, 2008, DOI:10.3970/cmes.2008.036.065

    Abstract A novel node-based smoothing element for triangular and quadrilateral meshes is presented for static analysis of planar piezoelectric structures. In contrast to the smoothed finite element formulation that was based on sub-cells within an original quadrilateral element, this new method transforms a general original finite element mesh into a mesh of new smoothing cells individually associated with a single node which is termed as node-based elements. The displacement fields of the element are approximated by the linear interpolation functions of the original mesh while the approximations of mechanical strains and electric potential fields are normalized More >

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