COLLECTIONS

Documents published in Scipedia

• A finite point method for three-dimensional compressible flow

  E. Ortega, E. Oñate, S. Idelsohn

  (2007). Research Report, Nº PI310

  
  

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• Analysis of ship hydrodynamics using the overlapping domain decomposition level set method

  K. Lam

  (2007). Research Report, Nº PI307

  
  

  Abstract

  This report investigates the free surface capture of the Overlapping Domain Decomposition Level Set Method (ODDLS). The CFD software Tdyn is used to carry out computations in unison with GiD a pre/post processor to prepare the model and to analysis data. The Arbitrary Lagrangian-Eulerian method is also applied to allow deformation of the model mesh to allow the hull to sink and trim and to optimise free surface capture. The offshore patrol vessel NT-130 developed by Navtec in Chile is the focus of the computations. Experimental towing tank data for still water conditions was compared to Tdyn results to asses its performance. Also, data from tests in wave conditions is presented in this report.

  Abstract
  This report investigates the free surface capture of the Overlapping Domain Decomposition Level Set Method (ODDLS). The CFD software Tdyn is used to carry out computations [...]

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• Shape optimization in aeronautical applications using neural networks

  A. Daring, R. López, R. Flores, G. Bugeda, E. Oñate

  (2007). Research Report, Nº PI306

  
  

  Abstract

  An optimization methodology based on neural networks was developed for use in 2D optimal shape design problems. Neural networks were used as a parameterization scheme to represent the shape function, and an edge-based high-resolution scheme for the solution of the compressible Euler equations was used to model the flow around the shape. The global system incorporates neural networks and the Euler fluid solver into the C++ Flood optimization framework containing a library of optimization algorithms. The optimization scheme was applied to a minimal drag problem in an unconstrained optimization case and a constrained case in hypersonic flow using evolutionary training algorithms. The results indicate that the minimum drag problem is solved to a high degree of accuracy but at high computational cost. For more complex shapes, parallel computing methods are required to reduce computational time.

  Abstract
  An optimization methodology based on neural networks was developed for use in 2D optimal shape design problems. Neural networks were used as a parameterization scheme to represent [...]

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• Drag prediction system based on neural networks

  I. Ortigoza, J. García-Espinosa

  (2007). Research Report, Nº PI305

  
  

  Abstract

  In this work we will be based on two experimental-based statistical techniques, which allow us to determine approximately the residual resistance coefficient of the sailboat and the viscous coefficient and wave resistance coefficient in the case of merchants. For the calculation of the residual resistance in sailboats the most used method is the Delft series, and for the calculation of the residual resistance in merchants the most widespread method is that of Holtrop and Mennen. Both methods used experimental data to adjust a function, the results obtained with the functions are quite reliable, but it is difficult to improve the model since the statistical adjustment is complicated. For this reason, in this work we try to overcome that limitation and develop a tool that is capable of performing the same calculations, with the same or better reliability and also that allows to be constantly improved with experimental data. The tool used is the neural network.

  Abstract
  In this work we will be based on two experimental-based statistical techniques, which allow us to determine approximately the residual resistance coefficient of the sailboat [...]

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• Computation of turbulent flows using a finite element formulation

  E. Oñate, A. Valls, J. García-Espinosa

  (2007). Research Report, Nº PI304

  
  

  Abstract

  We present a formulation for analysis of turbulent incompressible flows using a stabilized finite element method (FEM) based on the finite calculus (FIC) procedure. The stabilization terms introduced by the FIC approach allow to solve a wide range of fluid flow problems at different Reynolds numbers, including turbulent flows, without the need of a turbulence model. Examples of application of the FIC/FEM formulation to the analysis of 2D and 3D incompressible flows at large Reynolds numbers exhibiting turbulence features are presented.

  Abstract
  We present a formulation for analysis of turbulent incompressible flows using a stabilized finite element method (FEM) based on the finite calculus (FIC) procedure. The stabilization [...]

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• Enhanced Rotation-Free Basic Shell Triangle. Applications to Sheet Metal Forming

  E. Oñate, F. Flores, L. Neamtu

  (2007). Research Report, Nº PI302

  
  

  Abstract

  An enhanced rotation-free three node triangular shell element (termed EBST) is presented. The element formulation is based on a quadratic interpolation of the geometry in terms of the six nodes of a patch of four triangles associated to each triangular element. This allows to compute an assumed constant curvature field and an assumed linear membrane strain field which improves the in-plane behaviour of the element. A simple and economic version of the element using a single integration point is presented. The implementation of the element into an explicit dynamic scheme is described. The efficiency and accuracy of the EBST element and the explicit dynamic scheme are demonstrated in many examples of application including the analysis of a cylindrical panel under impulse loading and sheet metal stamping problems.

  Abstract
  An enhanced rotation-free three node triangular shell element (termed EBST) is presented. The element formulation is based on a quadratic interpolation of the geometry in [...]

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• Membranes structures formed by low pressure inflatable tubes. New analysis methods and recent constructions

  E. Oñate, F. Flores, J. Marcipar

  (2007). Research Report, Nº PI303

  
  

  Abstract

  This paper shows applications of a recently developed thin shell element adequate for the analysis of membrane and inflatable structures. The element is a three node triangle with only translational degrees of freedom that uses the configuration of the three adjacent elements to evaluate the strains in terms of the nodal displacements only. This allows to compute (constant) bending strains and (linear) membrane strains using a total Lagrangian formulation. Several examples, including inflation and deflation of membranes and some practical applications to the analysis, design and construction of membrane structures formed by low pressure inflatable tubes are presented.

  Abstract
  This paper shows applications of a recently developed thin shell element adequate for the analysis of membrane and inflatable structures. The element is a three node triangle [...]

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• NURBS-Enhanced finite element method for eular equations

  R. Sevilla, S. Fernández-Méndez, A. Huerta

  (2007). Research Report, Nº PI309

  
  

  Abstract

  In this work the NURBS-Enhanced Finite Element Method (NEFEM) is combined with a Discontinuous Galerkin (DG) formulation for the numerical solution of the Euler equations of gas dynamics. With the NEFEM approach numerical fluxes along curved boundaries are computed much more accurately due to the exact geometric representation of the computational domain. The proper implementation of the wall boundary condition provides accurate results even with a linear interpolation of the solution. A detailed comparison of the NEFEM in front of isoparametric finite elements (FE) is presented, demonstrating the superiority of the NEFEM approach for both linear and higher order computations.

  Abstract
  In this work the NURBS-Enhanced Finite Element Method (NEFEM) is combined with a Discontinuous Galerkin (DG) formulation for the numerical solution of the Euler equations [...]

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• NURBS-Enhanced finite element methods (NEFEM)

  R. Sevilla, S. Fernández-Méndez, A. Huerta

  (2007). Research Report, Nº PI308

  
  

  Abstract

  An improvement of the classical finite element method is proposed. It is able to exactly represent the geometry by means of the usual CAD description of the boundary with Non-Uniform Rational B-Splines (NURBS). Here, the two-dimensional case is presented. For elements not intersecting the boundary, a standard finite element interpolation and numerical integration is used. But elements intersecting the NURBS boundary need a specifically designed piecewise polynomial interpolation and numerical integration. A priori error estimates are also presented. Finally, some examples demonstrate the applicability and benefits of the proposed methodology. NEFEM is at least one order of magnitude more precise than the corresponding isoparametric finite element in every numerical example shown. This is the case for both continuous and discontinuous Galerkin formulations. Moreover, for a desired precision NEFEM is also more computational efficient, as shown in the numerical examples. The use of NEFEM is strongly recommended in the presence of curved boundaries and/or when the boundary of the domain has complex geometric details. The possibility of computing accurate solution with coarse meshes and high order interpolations, makes NEFEM a more efficient strategy than classical isoparametric FE.

  Abstract
  An improvement of the classical finite element method is proposed. It is able to exactly represent the geometry by means of the usual CAD description of the boundary with [...]

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• Posibilidades de los métodos numéricos en obras subterráneas

  E. Oñate, B. Suárez, J. Canet

  (2007). Research Report, Nº PI301

  
  

  Abstract

  Se presenta un resumen de las posibilidades de diversos métodos numéricos basados en la combinación de técnicas de elementos finitos y de partículas para la simulación de problemas típicos de obras subterráneas, tales como la excavación de túneles y la inundación de cavidades.

  Abstract
  Se presenta un resumen de las posibilidades de diversos métodos numéricos basados en la combinación de técnicas de elementos finitos y de partículas [...]

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