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  • 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 free stream conditions and geometry.… More >

  • Open Access


    Uncertainty Quantification of the Interaction of a Vortex Pair With the Ground

    J.L. Sereno1, J.C.F. Pereira1

    CMES-Computer Modeling in Engineering & Sciences, Vol.73, No.1, pp. 23-44, 2011, DOI:10.3970/cmes.2011.073.023

    Abstract The evolution of a two-dimensional vortex pair in ground effect was studied under the influence of random initial inputs comprising vortex strength (circulation) or initial vortex position. The paper addresses the questions of how do variations and uncertainties of initial conditions translate to the variability of vortex pair evolution. The stochastic solutions were obtained recurring to the Polynomial Chaos Expansion method of random processes applied to the Navier-Stokes equations for a laminar flow. The method quantifies the extent, dependence and propagation of uncertainty through the model system and, in particular, a methodology for the calculation of the vortices trajectory variability,… More >

  • Open Access


    On Chaos Control in Uncertain Nonlinear Systems

    Veturia Chiroiu1, Ligia Munteanu2, Ioan Ursu3

    CMES-Computer Modeling in Engineering & Sciences, Vol.72, No.3, pp. 229-246, 2011, DOI:10.3970/cmes.2011.072.229

    Abstract Chaotic behavior of uncertain nonlinear systems offers a rich variety of orbits, which can be controlled by bounding the signals involved in closed-loop systems. In this paper, systems with nonlinear uncertainties with no prior knowledge of their bounds, unmodeled dynamic law and rapidly varying disturbances are analyzed in order to propose a stabilization controller of the chaotic behavior via the fuzzy logic systems. More >

  • Open Access


    Investigation of Multi Geometric Uncertainties by Different Polynomial Chaos Methodologies Using a Fictitious Domain Solver

    L. Parussini1, V. Pediroda2

    CMES-Computer Modeling in Engineering & Sciences, Vol.23, No.1, pp. 29-52, 2008, DOI:10.3970/cmes.2008.023.029

    Abstract In this paper different Polynomial Chaos methods coupled to Fictitious Domain approach have been applied to one- and two- dimensional elliptic problems with multi uncertain variables in order to compare the accuracy and convergence of the methodologies. Both intrusive and non-intrusive methods have been considered, with particular attention to their employment for quantification of geometric uncertainties. A Fictitious Domain approach with Least-Squares Spectral Element approximation has been employed for the analysis of differential problems with uncertain boundary domains. Its main advantage lies in the fact that only a Cartesian mesh, that represents the enclosure, needs to be generated. Excellent accuracy… More >

  • Open Access


    Fictitious Domain with Least-Squares Spectral Element Method to Explore Geometric Uncertainties by Non-Intrusive Polynomial Chaos Method

    L. Parussini1, V. Pediroda2

    CMES-Computer Modeling in Engineering & Sciences, Vol.22, No.1, pp. 41-64, 2007, DOI:10.3970/cmes.2007.022.041

    Abstract In this paper the Non-Intrusive Polynomial Chaos Method coupled to a Fictitious Domain approach has been applied to one- and two-dimensional elliptic problems with geometric uncertainties, in order to demonstrate the accuracy and convergence of the methodology. The main advantage of non-intrusive formulation is that existing deterministic solvers can be used. A new Least-Squares Spectral Element method has been employed for the analysis of deterministic differential problems obtained by Non-Intrusive Polynomial Chaos. This algorithm employs a Fictitious Domain approach and for this reason its main advantage lies in the fact that only a Cartesian mesh needs to be generated. Excellent… More >

  • Open Access


    A Novel Improved Bat Algorithm in UAV Path Planning

    Na Lin1, Jiacheng Tang1, Xianwei Li2,3, Liang Zhao1,*

    CMC-Computers, Materials & Continua, Vol.61, No.1, pp. 323-344, 2019, DOI:10.32604/cmc.2019.05674

    Abstract Path planning algorithm is the key point to UAV path planning scenario. Many traditional path planning methods still suffer from low convergence rate and insufficient robustness. In this paper, three main methods are contributed to solving these problems. First, the improved artificial potential field (APF) method is adopted to accelerate the convergence process of the bat’s position update. Second, the optimal success rate strategy is proposed to improve the adaptive inertia weight of bat algorithm. Third chaos strategy is proposed to avoid falling into a local optimum. Compared with standard APF and chaos strategy in UAV path planning scenarios, the… More >

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