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  • Open Access

    ARTICLE

    Factorial Experiment Design in the Front Velocity Modeling Approach Applied to Chromatographic Separation of Glucose and Fructose

    A. Prieto-Moreno1, L.D.Tavares Câmara2, O. Llanes-Santiago1, A. J. Silva Neto2

    CMES-Computer Modeling in Engineering & Sciences, Vol.106, No.6, pp. 441-462, 2015, DOI:10.3970/cmes.2015.106.441

    Abstract This work deals with a statistical approach to the uncertainty propagation analysis when estimating the kinetic mass transfer parameters used to model a chromatographic column in the Simulated Moving Bed. The chromatographic column modeling was performed using the new front velocity approach. The uncertainty propagation analysis of operational factors intervening in the chromatographic process to estimated parameters was made using the response surface methodology. The application of the factorial experimental design allowed us to establish those operational factors showing a greater influence on continuous chromatography. Besides, the chromatographic regions, where factors cause a greater output variation as well as their… More >

  • Open Access

    ARTICLE

    Variance-based Sensitivity Analyses of Piezoelectric Models

    T. Lahmer1, J. Ilg2, R. Lerch2

    CMES-Computer Modeling in Engineering & Sciences, Vol.106, No.2, pp. 105-126, 2015, DOI:10.3970/cmes.2015.106.105

    Abstract In the recent years many publications appeared putting emphasis on the simulation-based identification of piezoelectric material parameters from electrical or mechanical measurements and combinations of them. By experience, one is aware of the importance of a single input parameter. However, it is not yet fully understood and in particular quantified to which extend missing knowledge in the single parameters (parameter uncertainty) influences the quality of the model's prognosis. In this paper, we adapt and apply variance-based sensitivity measures to models describing the piezoelectric effect in the linear case and derive global information about the single input parameter's sensitivities. More >

  • Open Access

    ARTICLE

    Long-term Analyses of Concrete-Filled Steel Tubular Arches Accounting for Interval Uncertainty

    Yong-Lin Pi1, Mark Andrew Bradford1

    CMES-Computer Modeling in Engineering & Sciences, Vol.99, No.3, pp. 233-253, 2014, DOI:10.3970/cmes.2014.099.233

    Abstract Creep and shrinkage of the concrete core of a concrete-filled steel tubular (CFST) arch under sustained loading are inevitable, and cause a long-term change of the equilibrium configuration of the CFST arch. As the equilibrium configuration changes continuously, the long-term radial and axial displacements of the CFST arch, stress distributions as well as the internal forces in the steel tube and the concrete core change substantially with time. Creep and shrinkage of the concrete core are related to a number of its material parameters such as its creep coefficient, aging coefficient, and shrinkage strain. The values of these parameters differ… More >

  • Open Access

    ARTICLE

    Constrained Optimization Multi-dimensional Harmonic Balance Method for Quasi-periodic Motions of Nonlinear Systems

    Haitao Liao1

    CMES-Computer Modeling in Engineering & Sciences, Vol.95, No.3, pp. 207-234, 2013, DOI:10.3970/cmes.2013.095.207

    Abstract The constrained optimization multi-dimensional harmonic balance method for calculating the quasi-periodic solutions of nonlinear systems is presented. The problem of determining the worst quasi-periodic response is transformed into a nonlinear optimization problem with nonlinear equality constraints. The general nonlinear equality constraints are built using a set of nonlinear algebraic equations which is derived using the multi-dimensional harmonic balance method. The Multi- Start algorithm is adopted to solve the resulting constrained maximization problem. Finally, the validity of the proposed method is demonstrated with a Duffing oscillator and numerical case studies for problems with uncertainties are performed on a nonlinear two-degree of… More >

  • Open Access

    ARTICLE

    Faster Than Real Time Stochastic Fire Spread Simulations

    A.R.Ervilha1,2, F.A.Sousa1, J.M.C.Pereira1, J.C.F.Pereira1

    CMES-Computer Modeling in Engineering & Sciences, Vol.89, No.5, pp. 361-387, 2012, DOI:10.3970/cmes.2012.089.361

    Abstract Faster than real time stochastic fire spread predictions are reported using a Non-Intrusive Spectral Projection (NISP) method based on Polynomial Chaos expansion and Graphic Processing Units (GPUs). The fireLib BEHAVE model together with a raster surface fire growth algorithm was implemented using the Compute Unified Device Architecture (CUDA) programming language. The uncertainty generated by the four random variables considered (wind speed, wind direction, fuel moisture, and fuel load) is quantified in the stochastic solution. Stochastic simulation of an idealized vegetation fire in a realistic complex terrain is obtained with speed-ups as high as 176 when compared to Central Processing Unit… More >

  • Open Access

    ARTICLE

    An Approach to Uncertainty Analysis of Rockfall Simulation

    S. Turrin1, M. Hanss1, A.P.S. Selvadurai2

    CMES-Computer Modeling in Engineering & Sciences, Vol.52, No.3, pp. 237-258, 2009, DOI:10.3970/cmes.2009.052.237

    Abstract Despite the continuing advances in rockfall analysis, the mathematical modeling and simulation of rockfall phenomena continues to be significantly influenced by a large amount of aleatory and epistemic uncertainty on significant number of model parameters. This paper focuses on the representation and quantification of epistemic uncertainties in rockfall modeling and simulation by fuzzy numbers. The propagation of the epistemic uncertainties considered is then calculated by the transformation method as a practical implementation of fuzzy arithmetic. Epistemic uncertainties on the material properties, on the boulder geometry and dimensions, on the kinematics of the impact and on the contact response between boulder… More >

  • Open Access

    ARTICLE

    Uncertainty Analysis for a Particle Model of Granular Chute Flow

    F. Fleissner1, T. Haag2, M. Hanss2, P. Eberhard1

    CMES-Computer Modeling in Engineering & Sciences, Vol.52, No.2, pp. 181-196, 2009, DOI:10.3970/cmes.2009.052.181

    Abstract In alpine regions human settlements and infrastructure are at risk to be hit by landslides or other types of geological flows. This paper presents a new approach that can aid the design of protective constructions. An uncertainty analysis of the flow around a debris barrier is carried out using a chute flow laboratory model of the actual debris flow. A series of discrete element simulations thereby serves to compare and assess two different barrier designs. In this study, the transformation method of fuzzy arithmetic is used to investigate the influence of epistemically uncertain model parameters. It turns out that parameter… More >

  • Open Access

    ARTICLE

    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

    ARTICLE

    A Computational Inverse Technique for Uncertainty Quantification in an Encounter Condition Identification Problem

    W. Zhang1, X. Han1,2, J. Liu1, R. Chen1

    CMES-Computer Modeling in Engineering & Sciences, Vol.86, No.5, pp. 385-408, 2012, DOI:10.3970/cmes.2012.086.385

    Abstract A novel inverse technique is presented for quantifying the uncertainty of the identified the results in an encounter condition identification problem. In this technique, the polynomial response surface method based on the structure-selection technique is first adopted to construct the approximation model of the projectile/target system, so as to reduce the computational cost. The Markov Chain Monte Carlo method is then used to identify the encounter condition parameters and their confidence intervals based on this cheap approximation model with Bayesian perspective. The results are demonstrated through the simulated test cases, which show the utility and efficiency of the proposed technique.… More >

  • Open Access

    ARTICLE

    An Adaptive Extended Kalman Filter Incorporating State Model Uncertainty for Localizing a High Heat Flux Spot Source Using an Ultrasonic Sensor Array

    M.R. Myers1, A.B. Jorge2, D.E. Yuhas3, D.G. Walker1

    CMES-Computer Modeling in Engineering & Sciences, Vol.83, No.3, pp. 221-248, 2012, DOI:10.3970/cmes.2012.083.221

    Abstract An adaptive extended Kalman filter is developed and investigated for a transient heat transfer problem in which a high heat flux spot source is applied on one side of a thin plate and ultrasonic pulse time of flight is measured between spatially separated transducers on the opposite side of the plate. The novel approach is based on the uncertainty in the state model covariance and leverages trends in the extended Kalman filter covariance to drive changes to the state model covariance during convergence. This work is an integral part of an effort to develop a system capable of locating the… More >

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