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• Desarrollo del código de elementos finitos TDYN para estudio de la hidrodinámica de barcos. Aplicaciones al diseño de veleros de la Copa América.

  E. Oñate, J. García-Espinosa

  (2004). Research Report, Nº PI246

  
  

  Abstract

  En los últimos años CIMNE ha desarrollado en colaboración con la empresa COMPASS Ingeniería y Sistemas, S.A. (www.compassis.com) un nuevo código de cálculo basado en el método de los elementos finitos para el estudio fluido-dinámico de embarcaciones. El código permite reproducir de forma virtual con fidelidad el denominado “Canal de Ensayos Hidrodinámicos” (CEH) utilizado regularmente para la evaluación experimental de la resistencia hidrodinámica de barcos. El nuevo código, denominado TDYN, es una alternativa a mucho más económica y precisa a los ensayos en el CEH, al permitir analizar el comportamiento de barcos en el agua a escala real, eliminando así los errores de escala usuales en los ensayos experimentales. TDYN incorpora nuevos modelos matemáticos y métodos de elementos finitos avanzados que han llevado a término numerosas publicaciones internacionales. TDYN se desarrolló conjuntamente por investigadores de la Universidad Politécnica de Catalunya (UPC) del Depto. De Resistencia de Materiales y Estructuras de la Escuela Técnica Superior de Ingenieros de Caminos, Canales y Puertos de Barcelona y del Departamento de Ciencia e Ingenieros Náuticas de la Facultad de Náutica de Barcelona en el marco de diversos proyectos europeos y nacionales llevados a término en colaboración con CIMNE y la empresa COMPASS, además de otras empresas de prestigio en el sector naval. TDYN se aplicó al diseño de diversos veleros de la Copa América (en particular por el equipo del barco ALINGHI ganador de la edición de 2003). TDNY lo comercializa actualmente en todo el mundo la empresa COMPASS, una spin-off de la UPC.  

  Abstract
  En los últimos años CIMNE ha desarrollado en colaboración con la empresa COMPASS Ingeniería y Sistemas, S.A. (www.compassis.com) un nuevo código [...]

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• Programación y gestión de redes de notas via Internet I

  J. Jiménez, A. Priegue, F. Guzmán, E. Oñate

  (2005). Research Report, Nº PI279

  
  

  Abstract

    Este trabajo presenta los desarrollos llevados a cabo en CIMNE en la programación y gestión de redes de motas utilizando Internet. El trabajo se enmarca dentro de la línea de I+D de CIMNE en el estudio, desarrollo y aplicación de redes de sensores inteligentes sin hilos en diversos ámbitos de la ingeniería. En las referencias [(1-3)] se describen los resultados de investigaciones anteriores del equipo de CIMNE sobre el tema. El trabajo se ha llevado a cabo en el marco de las actividades del proyecto "Desarrollo de tecnologías para investigación y gestión de procesos constructivos utilizando redes de sensores sin hilos.(PROSENSOR)" financiado por el programa PROFIT del Ministerio de Educación y Ciencia. El proyecto se inició en Noviembre de 2005 y su finalización está prevista en Diciembre, 2007. Los autores agradecen a la empresa Sensoria S.A., el asesoramiento y colaboración en la realización del trabajo.

  Abstract
    Este trabajo presenta los desarrollos llevados a cabo en CIMNE en la programación y gestión de redes de motas utilizando Internet. El trabajo se enmarca [...]

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• Plataforma WSN/NIMS I

  J. Piazzese, J. Jiménez, E. Oñate

  (2005). Research Report, Nº PI268

  
  

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• El método de partículas y elementos finitos. Aplicaciones en ingeniería de puertos

  E. Oñate, M. Celigueta, S. Idelsohn, F. Del Pin

  (2005). Research Report, Nº PI278

  
  

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• Plataforma WSN/NIMS III. Programación básica de motas

  J. Jiménez, A. Priegue, J. Piazzese, E. Oñate

  (2005). Research Report, Nº PI277

  
  

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• An edge-based solver for compressible flow

  E. Ortega, R. Flores, E. Oñate

  (2005). Research Report, Nº PI275

  
  

  Abstract

  An edge-based high-resolution scheme for the solution of the compressible Euler equations on unstructured finite elements grids is presented. The flow solver adopted in the present work is the approximate Riemann solver developed by Roe. A high-order spatial approximation is achieved by means of a piecewise linear reconstruction of the interface variables according to the MUSCL (Monotone Upstream-centered Schemes for Conservation Laws) formulation. Finally, non-linear limiters are introduced in order to prevent the generation of oscillations. The proposed approach corresponds with the methodology presented by Löhner in [1].

  Abstract
  An edge-based high-resolution scheme for the solution of the compressible Euler equations on unstructured finite elements grids is presented. The flow solver adopted in the [...]

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• Plataforma WSN/NIMS II. Primeras experiencias en CIMNE

  J. Jiménez, A. Priegue, E. Oñate

  (2005). Research Report, Nº PI272

  
  

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• Evolutionary methods for optimal shape design

  A. Fung, E. Pahl, G. Bugeda, E. Oñate

  (2005). Research Report, Nº PI270

  
  

  Abstract

  An optimization code called Optima has been developed at the International Centre for Numerical Methods in Engineering (CIMNE). This report validates two reputably robust Evolutionary Algorithms available in Optima and employs them on aerodynamic shape optimization problems. The two schemes, Differential Evolution Scheme 1 (DE1) and Evolution Strategy coupled with Covariance Matrix Adaptation (ES-CMA), were tested and verified on three standard parametric optimization objective functions through comparison against existing results. Analysis of the test data allowed trends to be established and from this, settings to enhance the performance of the algorithms were proposed and substantiated. The algorithms and their suggested settings were applied on an inverse and a direct constrained shape optimization problem involving NACA four digit airfoils. The inverse task involves the recovery of an airfoil profile through its pressure distribution combination of lift and drag coefficients. Simulation of the airfoil in turbulent flow was done using a Computational Fluid Dynamics (CFD) setup. Finally, the results are presented and the ES-CMA method, using the setting CMA-B proposed in this paper, was found to be most robust. Suggestions for improvements and further work in the optimization configuration and the problem simulation are also proposed.  

  Abstract
  An optimization code called Optima has been developed at the International Centre for Numerical Methods in Engineering (CIMNE). This report validates two reputably robust [...]

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• Modeling bed erosion in free surface flows by the particle finite element method

  E. Oñate, M. Celigueta, S. Idelsohn

  (2006). Research Report, Nº PI293

  
  

  Abstract

  We present a general formulation for modeling bed erosion in free surface flows using the particle finite element method (PFEM). The key feature of the PFEM is the use of an updated Lagrangian description to model the motion of nodes (particles) in domains containing fluid and solid subdomains. Nodes are viewed as material points (called particles) which can freely move and even separate from the fluid and solid subdomains representing, for instance, the effect of water drops or soil/rock particles. A mesh connects the nodes defining the discretized domain in the fluid and solid regions where the governing equations, expressed in an integral form, are solved as in the standard FEM. The necessary stabilization for dealing with the incompressibility of the fluid is introduced via the finite calculus (FIC) method. An incremental iterative scheme for the solution of the nonlinear transient coupled fluid-structure problem is described. The erosion mechanism is modeled by releasing the material adjacent to the bed surface according to the frictional work generated by the fluid shear stresses. The released bed material is subsequently transported by the fluid flow. Examples of application of the PFEM to solve a number of bed erosion problems involving large motions of the free surface and splashing of waves are presented.

  Abstract
  We present a general formulation for modeling bed erosion in free surface flows using the particle finite element method (PFEM). The key feature of the PFEM is the use of [...]

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• LES turbulence models. Relation with stabilized numerical methods

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

  (2006). Research Report, Nº PI288

  
  

  Abstract

  One of the aims of this text is to show some important results in LES modelling and to identify which are main mathematical problems for the development of a complete theory. A relevant aspect of LES theory, which we will consider in our work, is the close relationship between the mathematical properties of LES models and the numerical methods used for their implementation. In last years it is more and more common the idea in the scientific community, especially in the numerical community, that turbulence models and stabilization techniques play a very similar role. Methodologies used to simulate turbulent flows, RANS or LES approaches, are based on the same concept: unability to simulate a turbulent flow using a finite discretization in time and space. Turbulence models introduce additional information (impossible to be captured by the approximation technique used in the simulation) to obtain physically coherent solutions. On the other side, numerical methods used for the integration of partial differential equations (PDE) need to be modified in order to able to reproduce solutions that present very high localized gradients. These modifications, known as stabilization techniques, make possible to capture these sharp and localized changes of the solution. According with previous paragraphs, the following natural question appears: Is it possible to reinterpret stabilization methods as turbulence models? This question suggests a possible principle of duality between turbulence modelling and numerical stabilization. More than to share certain properties, actually, it is suggested that the numerical stabilization can be understood as turbulence. The opposite will occur if turbulence models are only necessary due to discretization limitations instead of a need for reproducing the physical behaviour of the flow. Finally: can turbulence models be understood as a component of a general stabilization method?

  Abstract
  One of the aims of this text is to show some important results in LES modelling and to identify which are main mathematical problems for the development of a complete theory. [...]

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