ABSTRACT
Introducción: La Isla del Coco por su ubicación en el océano Pacífico y en aguas profundas, periódicamente arriban olas energéticas que se originan en el Océano del Sur. La isla actúa como un abrigo disipando parte de la energía de las olas que llegan a la costa pacífica de Costa Rica. Objetivo: El objetivo del trabajo es caracterizar las condiciones generales del oleaje a través de la simulación numérica del oleaje en el Pacífico Tropical del Este (PTE), con especial interés en la Isla del Coco. Métodos: Las olas se propagan con el modelo espectral de oleaje WAVEWATCH III. Se usa en el modelo una malla no estructurada. Se utilizan dos años (2007-2008) de datos históricos de oleaje como condiciones de frontera obtenidos de reanálisis con el modelo WAVEWATCH generado por el Instituto Francés para la Investigación del Mar (IFREMER por sus siglas en francés). Se obtienen mapas anuales y estacionales y series temporales de la altura significante de la ola, periodo y dirección asociado al pico del espectro de energía. Resultados: Los resultados mostrados son similares a otros estudios previos de simulación y observación. El campo de oleaje es caracterizado por periodos largos y dirección desde suroeste en promedio. Las condiciones de oleaje sobre la isla obedecen a los sistemas extratropicales de ambos hemisferios y a procesos locales en el PTE. Conclusiones: El modelo de olas WAVEWATCH III mostró que representa las condiciones típicas de oleaje en los alrededores de la Isla del Coco. Es el primer trabajo de simulación de oleaje aplicando una malla no convencional en la zona económica exclusiva de Costa Rica. El estudio sirve como base para extenderse a otras áreas específicas de la costa.
Introduction: Periodically energetic waves, originated in the Southern Ocean, arrive to Cocos Island, because of its location in the Pacific Ocean and in deep waters. The island acts as a shelter dissipating part of the energy of the waves that reach the Pacific coast of Costa Rica. Objetive: The objective of the work is to characterize the general conditions of the swell through the numerical simulation of the swell in the Eastern Tropical Pacific (ETP), with special interest in Cocos Island. Methods: The waves are propagated with the WAVEWATCH III wave spectral model. An unstructured mesh is used in the model. Two years (2007-2008) of hindcast data are used as boundary conditions obtained from reanalysis with the WAVEWATCH model, generated by the French Institute for Marine Research (IFREMER for its acronym in French). Annual and seasonal maps and time series of significant wave height, peak period and peak wave direction are obtained. Results: The results shown are similar to other previous simulation and observation studies. The mean wave field is characterized by long periods from southwest direction. The wave conditions on the island obey the extratropical systems of both hemispheres and local processes in the PTE. Conclusions: The WAVEWATCH III wave model showed that it represents the typical wave conditions in the surroundings of Cocos Island. It is the first wave simulation work applying an unconventional mesh in the exclusive economic zone of Costa Rica. The study serves as a basis for extending to other specific areas of the coast.
ABSTRACT
Objective To study high-quality and high efficient meshing methods for skeleton. Methods Based on characteristics of bone structure, the mesh generation technology of computational fluid dynamics (CFD) was applied in mesh generation for bone biomechanics. Hexahedron elements and tetrahedron elements were used to simulate cortical bone and cancellous bone, respectively. Results By using CFD mesh generation technology, high-quality hexahedral elements could be obtained, the structure characteristics of skeleton could be preferably simulated, and computer automatic meshing could be implemented. The amount of time for meshing bones by the new method was only about 1/5 of that by the traditional method, and the calculation results obtained from the finite element model were basically consistent with the results from the cadaver experiment. Conclusions The CFD mesh generation technology can be applied in the field of bone biomechanics, which provides an effective approach to reconstruct complex human skeleton.
ABSTRACT
Objective To study high-quality and high efficient meshing methods for skeleton.Methods Based on characteristics of bone structure,the mesh generation technology of computational fluid dynamics (CFD) was applied in mesh generation for bone biomechanics.Hexahedron elements and tetrahedron elements were used to simulate cortical bone and cancellous bone,respectively.Results By using CFD mesh generation technology,high-quality hexahedral elements could be obtained,the structure characteristics of skeleton could be preferably simulated,and computer automatic meshing could be implemented.The amount of time for meshing bones by the new method was only about 1/5 of that by the traditional method,and the calculation results obtained from the finite element model were basically consistent with the results from the cadaver experiment.Conclusions The CFD mesh generation technology can be applied in the field of bone biomechanics,which provides an effective approach to reconstruct complex human skeleton.
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Objective To develop an automatic segmentation and mesh generation technique for abdominal aortic aneurysm (AAA) and to build a 2D numerical analysis model that can be used for finite element analysis (FEA). Methods A method that totally based on morphology processing was developed to segment all the components of the AAA. For each closed curve that obtained, its signed distance function was then calculated. According to the set relationships between each curve, the final signed distance function was calculated. Under the control of this function and an equilibrium relationship, iterated Delaunay algorithms were used until the equilibrium relationship was satisfied or the set conditions were reached. Then the program ended and the finite element model was generated. Results Automatic segmentation of the lumen as well as semiautomatic segmentation of the wall and calcification were achieved. Different parts of the AAA were meshed, and the type and density of the mesh could be controlled. Two finite element models were established for stress analysis: one was the coupling mesh of the thrombus and the wall, and the other was the coupling mesh of the thrombus, the wall and the calcifications. Conclusions An automatic segmentation and mesh generation algorithm with high accuracy has been developed, without any complicated computation or initial curve. The mesh generation algorithm tends to produce high quality meshes and the generation is easy to be controlled by only two parameters. The generated mesh has been verified to be useful in FEA simulation.
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Objective To generate finite element models of human head based on segmented computer tomography data.Methods A four-step procedure was adopted to configure the coarse mesh.The method of longest edge propagation path and the edge collapse were used to refine and optimize the final mesh.The method was evaluated by means of computer simulations in a 3-concentric-sphere head model and a three-layer realistic geometry human head model.Results The present simulation results showed reliability and rationality of the finite element computation,thus indicate the suitability of the developed method.Conclusion A multi-tissue finite element model is obtained by using this method.It can be applied to the computation of finite element based bio-mechanics and bio-electromagnetism.