Documents published in Scipedia

• Estimation of kinetic parameters in a chromatographic separation model via Bayesian inference

  C. Oliveira, J. Junior, D. Knupp, A. Neto, A. Prieto-Moreno, O. Llanes-Santiago

  Rev. int. métodos numér. cálc. diseño ing. (2018). Vol. 34, (1), 26

  
  

  Abstract

  The modeling of adsorption processes appears quite frequently in the chemical industry, petrochemical plants and refineries, for example for separation and purification of mixtures in Simulated Moving Bed (SMB) units. In the mathematical formulation, the accurate determination of the model parameters is an important step for the design of chromatographic conditions for continuous separation in SMB processes. This work is aimed at the estimation of the model parameters in adsorption processes, using a chromatographic column for the separation of glucose and fructose. The Bayesian framework for inverse problems is investigated through the implementation of Markov Chain Monte Carlo methods (MCMC) and a critical comparison against the classical Maximum Likelihood approach, with the minimization of the objective function via two different stochastic techniques, namely the Particle Collision Algorithm (PCA), and the Particle Swarm Optimization (PSO) is performed. Different cases are presented in order to investigate the statistical significance of the estimates obtained, and perform comparisons between the solution via Bayesian inference and via the minimization of the objective function with the stochastic methods. The results demonstrate that the Bayesian approach employs less computational effort to achieve estimates with comparable statistical information.

  Abstract
  The modeling of adsorption processes appears quite frequently in the chemical industry, petrochemical plants and refineries, for example for separation and purification of [...]

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• Simulation of the two-dimensional flow of the initiation channel of the Itaipu hydroelectric power plant by the lattice Boltzmann method

  J. Cargnelutti, V. Galina, E. Kaviski, L. Gramani, A. Lobeiro

  Rev. int. métodos numér. cálc. diseño ing. (2018). Vol. 34, (1), 25

  
  

  Abstract

  This paper analyzes the ability of the Lattice Boltzmann method (LBM) with multiple relaxation times (MRT) in the simulation of flow in practical engineering problems. The case study covered refers to the first section of the initiation channel, which is part of the piracema channel, located in the Itaipu Hydroelectric Power Plant. The initiation channel has submerged obstacles distributed from one margin to the other, in order to reduce water velocity and allow the piracema cycle to occur. The governing equations of flow are the shallow water equations, which will be solved through the LBM-MRT. The non-slip bounce-back scheme was used on walls and obstacles, constant discharge at the inlet and fixed depth at the outlet of the channel. Due to the characteristics of the problem to be simulated, a large eddy simulation (LES) technique was incorporated into the computational code, which allows to obtain results that are closer to the actual behavior of the flow. In addition, the stability of the simulation at all points of the mesh is evaluated for each step of time and, together with the property of the consistency of the LBM, the convergence of the solution is obtained. The simulation provides the depth, velocities in the x and y directions, and the magnitude of water vorticity.

  Abstract
  This paper analyzes the ability of the Lattice Boltzmann method (LBM) with multiple relaxation times (MRT) in the simulation of flow in practical engineering problems. The [...]

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• Analytical solution proposal for fast numerical algorithm in special structured higher order differential equations

  I. Derin, Y. Hames

  Rev. int. métodos numér. cálc. diseño ing. (2018). Vol. 34, (1), 21

  
  

  Abstract

  We suggest a practical method for obtaining the particular solution of non-homogeneous higher order linear differential equations with constant coefficients. The proposed method can be applied directly and simply to such problems. We revealed that is valid for the different type of problem by using sample solutions. This simple analytical solution that we have introduced will help to create a fast numerical algorithm for computers and thus simplify the numerical solutions of higher order physical problems.

  Abstract
  We suggest a practical method for obtaining the particular solution of non-homogeneous higher order linear differential equations with constant coefficients. The proposed [...]

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• Modal and dynamic analysis of a footbridge in service

  N. Frechilla, M. Cacho-Pérez, A. Lorenzana

  Rev. int. métodos numér. cálc. diseño ing. (2018). Vol. 34, (1), 18

  
  

  Abstract

  Civil engineering constructions like pedestrian footbridges are structures increasingly slender, ambitious and complex in which the dynamic effects caused by the loads to which they are subjected (pedestrians) may induce service problems and / or significant or repetitive amplifications of the efforts and deformations. This fact together with the current social demands related to the perception and comfort raise the need to integrate the analysis and computer-aided design in the evaluation of the vibrations generated by the loads this type of structures supports. In the specific case of finite element commercial programs, their use has not proliferated as much as in other engineering fields due to the existence of simplified methodologies in numerous national and international guidelines and regulations and the difficulty of making realistic models in the case of complex structures. However, the knowledge generated by the analysis of this type of numerical models would be especially useful in the earlier phases of the design of similar structures, so much initial as of the necessary modifications to solve existing dynamic problems, since it is in these stages when the best solution could be applied from both a technical and an economic point of view. This article describes the process of generation and updating of the mechanical finite element model (FEM) of a footbridge in service and the simulation of two types of load: an excitation generated by a shaker and a pedestrian load, contrasting the results generated by the numerical model with those obtained experimentally.

  Abstract
  Civil engineering constructions like pedestrian footbridges are structures increasingly slender, ambitious and complex in which the dynamic effects caused by the loads to [...]

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• Parallelization using a BDD-C of a multiscale strategy with non lineal localization based on a NKS

  J. Hinojosa, K. Saavedra, G. Pincheira

  Rev. int. métodos numér. cálc. diseño ing. (2018). Vol. 34, (1), 19

  
  

  Abstract

  In previous works, the nonlinear localization was first presented and studied in the case of large displacements but only for globally stable structural responses. In this paper, the parallelization of this computational strategy using a Balancing Domain Decomposition by Constrains (BDD-C) is presented. Finally, a validation of this implementation is carried out in lineal elasticity, verifying the ''speed-up'' and the numerical extensibility.

  Abstract
  In previous works, the nonlinear localization was first presented and studied in the case of large displacements but only for globally stable structural responses. In this [...]

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• Modeling the effects of high strain rate loading on RC columns using Arbitrary Lagrangian Eulerian (ALE) technique

  M. Abedini, A. Mutalib, S. Raman, E. Akhlaghi

  Rev. int. métodos numér. cálc. diseño ing. (2018). Vol. 34, (1), 24

  
  

  Abstract

  In recent years, many studies have been conducted by governmental and nongovernmental organizations across the world in an attempt to better understand the effect of explosive loads on buildings in order to better design against specific threats. This study is intended to contribute to increase the knowledge about how explosions affect reinforced concrete (RC) columns. In this study, a nonlinear model is developed to study the blast response of RC columns subjected to explosive loads. Numerical modeling of RC column under explosive load is presented using advanced finite element code LS DYNA. The obtained numerical model is validated with the experimental test and the results are in substantial agreement with the experimental data. ALE method for blast analysis is presented in the current research. The effects of scaled distance on the damage profile of RC columns are investigated. The results demonstrate that the level of damage increased with describing the scaled distance. Also the results shown duration for the blast loading, and hence the impulse, varies with charge masses at the specified scaled distance. Higher magnitude charge masses produced longer blast loading durations than lower magnitude charge masses. This means that at the same scaled distance, a charge mass of higher magnitude produced a higher impulse than the lower magnitude charge mass. The findings of this research represent the scaled distance is an important parameter that should be taken into account when analyzing the behavior of RC columns under explosive effects. The data collected from this research are being used to improve the knowledge of how structures will respond to a blast event, and improve finite element models for predicting the blast performance of concrete structures.

  Abstract
  In recent years, many studies have been conducted by governmental and nongovernmental organizations across the world in an attempt to better understand the effect of explosive [...]

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• Two-dimensional numerical simulation of channel flow with submerged obstacles using the lattice Boltzmann method

  J. Cargnelutti, V. Galina, E. Kaviski, L. Gramani, A. Lobeiro

  Rev. int. métodos numér. cálc. diseño ing. (2018). Vol. 34, (1), 20

  
  

  Abstract

  A two-dimensional numerical simulation of the water flow in a rectangular channel with submerged obstacles distributed alternately along its banks is presented. The governing equations of flow are the shallow water equations, which will be solved by the Boltzmann lattice method (LBM) with multiple relaxation times (MRT). The non-slip bounce-back scheme was used on walls and obstacles, constant discharge at the inlet and fixed depth at the outlet of the channel. Due to the characteristics of the problem to be simulated, a large eddy simulation (LES) technique was incorporated into the computational code, which allows to obtain results that are closer to the actual behavior of the flow. In addition, the stability of the simulation at all points of the mesh is evaluated for each step of time and, together with the property of the consistency of the LBM, the convergence of the solution is obtained. The simulation provides the depth, velocities in the x and y directions, and the magnitude of water vorticity.

  Abstract
  A two-dimensional numerical simulation of the water flow in a rectangular channel with submerged obstacles distributed alternately along its banks is presented. The governing [...]

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• Nonlinear dynamic analysis of structures in contact with soil

  L. Rosas, A. Silva, R. Silveira

  Rev. int. métodos numér. cálc. diseño ing. (2018). Vol. 34, (1), 14

  
  

  Abstract

  Structural elements, in many situations, are supported by other surfaces, such as soil, which may offer movement constraints in some directions. Therefore, the static and dynamic analysis of these elements considering their interaction with the soil becomes important in the design of a structural design. This paper presents the nonlinear dynamic analysis of structural systems considering such interaction through the Finite Element Method. A geometrically nonlinear beam-column element is used to model the structure, while the soil can be idealized as a continuum foundation, through the Winkler and Pasternak models. It is assumed that the foundation reacts to tension and compression stresses, so during the deformation process the structural elements are subjected to bilateral contact constraints. The analysis is based on the modeling of the structural system using the finite element method, where the Newmark integration method and Newton-Raphson iterative strategy are used in the process of solving the nonlinear dynamic equations in the time domain. Practical situations involving the interaction between soil and structure were evaluated during the study, showing the influence of contact in the natural vibration frequency and transient response of these structures.

  Abstract
  Structural elements, in many situations, are supported by other surfaces, such as soil, which may offer movement constraints in some directions. Therefore, the static and [...]

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• Galoisian and numerical approach of three dimensional linear differential systems with skew symmetric matrices defined in a non- constant differential field

  P. Acosta-Humánez, M. Jiménez, J. Ospino-Portillo

  Rev. int. métodos numér. cálc. diseño ing. (2018). Vol. 34, (1), 8

  
  

  Abstract

  This work contrasts numerical methods with algebraic methods. These methods are applied to solve a three dimensional linear differential system with skew symmetric matrices defined in a non- constant differential field. Algorithms and methods of Differential Galois Theory, are used to provide an algebraic solution, while numerical methods, in particular, methods from Runge - Kutta family, are applied to the same system. Finally, the absolute and relative errors between Liouvillians solution are calculated comparing the solutions obtained by means of algebraic methods and by means of numerical methods.

  Abstract
  This work contrasts numerical methods with algebraic methods. These methods are applied to solve a three dimensional linear differential system with skew symmetric matrices [...]

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• Composite slabs micromechanics characterization of the steel-concrete interaction with finite element models

  A. Plans, D. Alamillo, M. Ferrer, F. Marimon

  Rev. int. métodos numér. cálc. diseño ing. (2018). Vol. 34, (1), 22

  
  

  Abstract

  This study focuses on the improvement of composite slabs characterization throughout the use of advanced finite elements models. The accurate three-dimensional modelling of a full scale commercial steel sheet and concrete slab geometries enables the analysis of the composite slab micromechanics. The inclusion of the embossments depth and slope, the steel sheet thickness, the tilting angle, the length and width and spacing of embossments, and the profiling angle of the rib shape removes the need of simplifications for the complex phenomenon at the steel – concrete interface. The accuracy observed at the finite element models once compared with the laboratory specimens enables a new approach to describe the complex stress distributions in composite slabs. In particular, this study introduces a novel representation of the longitudinal shear strength tu and a newly defined vertical normal stress σu between the steel and concrete that frequently define the overall composite slab bearing capacity. Subsequently, this study compares detailed stress diagrams and deformations from the finite elements models with experimental data obtained through piezoelectric gauges at the laboratory specimens.

  Abstract
  This study focuses on the improvement of composite slabs characterization throughout the use of advanced finite elements models. The accurate three-dimensional modelling of [...]

  • 263
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