Global ETD Search
Search theses and dissertations gathered from participating repositories worldwide. Every result links back to the library that holds it. No account is needed.
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Showing 1 to 20 of 37 for “"hexahedral"”.
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Generation and Optimization of Quadrilateral and Hexahedral Meshes
… the structure simplification of unstructured hexahedral (hex-) meshes that contain more complex scenarios due to the additional dimension. Even though the initial simplification results on some simple hex-meshes are promising, more works need to be done to extend the operations used in …
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Domain decomposition for hexahedral mesh generation using singularity lines
Generating automatically a hexahedral mesh for a 3D domain of arbitrary complexity is a challenging problem that has puzzled the research community considerably. As opposed to tetrahedral mesh generation, there is no existing algorithm that can operate with the push of a button and produce the …
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A Selective Approach to Hexahedral Refinement of Unstructured Conformal Meshes
Hexahedral refinement increases the density of an all-hexahedral mesh in a specified region, improving numerical accuracy. Previous research using solely sheet refinement theory made the implementation computationally expensive and unable to effectively handle multiply-connected transition elements …
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All Hexahedral Meshing of Multiple Source, Multiple Target, Multiple Axis Geometries Via Automatic Grafting and Sweeping
The development of algorithms for the automatic creation of finite element meshes composed entirely of hexahedra (all-hex) is an active area of research. All-hex meshes are desirable for their characteristic of high accuracy with a low node count. Sweeping is one of the most widely used algorithms …
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Adaptive Frame Fields for Polycube Generation and Quad Simplification
Hexahedral (hex) meshing is the problem of approximating a 3-dimensional volume with cube-like structures, and is used to discretize arbitrary volumes to solve PDEs. The structure of a hex mesh is largely guided by its singular graph. For a hex mesh to have good quality, the hexes must have …
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Computationally-effective Modeling of Far-field Underwater Explosion for Early-stage Surface Ship Design
… FEM. Second, a novel fully automatic all-hexahedral mesh generation scheme is applied to generate the fluid mesh. Along with the spectral element, the all-hex mesh shows greater accuracy than the all-tetrahedral finite element mesh which is typically used. This new meshing approach …
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Hamiltonian Paths and Strands for Unified Grid Approach for Computing Aerodynamic Flows
… a structured grid solver. A pure quadrilateral/hexahedral mesh is a prerequisite for the line identification and enables approximate factorization along the lines on the unstructured grid. Among various methods, subdivision is the easiest way to obtain a pure quadrilateral/hexahedral mesh from …
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An anisotropic adaptive method for the solution of 3-D inviscid and viscous compressible flows
… validated on various benchmark cases on both hexahedral and tetrahedral meshes. The numerical results obtained span inviscid and viscous flows, as well as internal and external aerodynamics. The effectiveness of the adaptive scheme to equidistribute the interpolation error over the edges of …
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Oxygen diffusion through titanium and other HCP metals
… interstitials in alpha-titanium, the octahedral, hexahedral, and crowdion sites. Transitions between these interstitial sites form a complex diffusion network in which almost all pathways contribute to diffusion. The interaction energy between oxygen and 45 substitutional solutes are calculated …
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Computational modeling and simulation of composite materials based on tomographic images
… element methodology. Although quadrilateral or hexahedral elements are obviously most natural in our context, IGFEM has primarily been used only with triangular elements in 2D and tetrahedral elements in 3D because of the much simpler implementation of the intersections of interfaces with mesh …
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Interior Node Projection Techniques in Sweeping Algorithms
… thesis. Sweeping is a method used to produce all-hexahedral finite element meshes on certain classes of geometry. The placement of nodes in the interior of the geometry during the sweeping process remains a difficult problem. This thesis presents advancements in this area which improve the speed …
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Surpassing Local Optimality in Geometry Processing
… to target cross-field based quad meshing, hexahedral mesh quality enhancement, and algebraic collision detection. With these tools, we manage to avoid shallower local minima and sometimes to reach or even surpass globally optimal solutions. We conclude with some principles by which these …
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A Parallel Solution-Adaptive Method for Turbulent Non-Premixed Combusting Flows
… body-fitted multi-block quadrilateral meshes and hexahedral meshes. The compressible formulation adopted herein can readily accommodate large density variations and thermo-acoustic phenomena. A preconditioned multigrid algorithm is used to obtain the solution on highly stretched meshes in a more …
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AEROMECHANICS OF A DOUBLE ANHEDRAL TIP COMPOSITE ROTOR: EXPERIMENT AND MODELING
… 3-D model was developed with CATIA (CAD), Cubit (hexahedral meshing), and X3D (aeromechanics). The 3-D CAD was constructed with guidance from Boeing to ensure the geometry was representative of a modern rotor yet generic enough to be open source for U.S. Gov-industry-academia joint study. The …
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Development and application of hybrid finite methods for solution of time dependent maxwell's equations
… specifically in the context of rectangular and hexahedral elements. Due to the Galerkin-type treatment of the hanging variables, the resulting FETD method has the same conditions of stability as those of the regular FETD method. Based on this method, an FDTD subgridding method with provable …
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Efficient finite-volume schemes for magnetohydrodynamic simulations in solar physics
… and local grid adaption on unstructured hexahedral or tetrahedral grids.<br><br>All our comparisons of solvers are based on considering their efficiencies, i.e., the computational time required for reaching the same errors. We construct one- and two-dimensional Riemann problems whose …
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Variational multiscale method for coupled systems: free-surface flows and stratified turbulence
… method for coupled systems is implemented using hexahedral and tetrahedral elements, and the code is parallelized for the distributed memory system. A range of problems is presented to show the mathematical and computational features of the method.
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Code Verification and Numerical Accuracy Assessment for Finite Volume CFD Codes
… elements in 2D and tetrahedral, prismatic, and hexahedral elements in 3D. The requirements of systematic mesh refinement are discussed, particularly in regards to unstructured meshes. Different code options verified include the baseline steady state governing equations, transport models, …
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3D FE simulation of the welding process to optimise residual stress profiles in complex geometries
… welded structures, a newly developed all-hexahedral meshing technique was employed to mesh the complex intersection area in a tee branch junction. The moving heat source and filler material deposition were simulated by assigning reactivated elements with a volumetric heat flux progressing …
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Numerical Analysis of Respiratory Aerosol Deposition: Effects of Exhalation, Airway Constriction and Electrostatic Charge
… on the transport and deposition of aerosols with hexahedral meshes being most accurate. Objective II: In order to evaluate the effects of bronchoconstriction under exhalation conditions, normal and constricted pediatric airway models were considered. Results include (i) a significant increase in …
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