2,148 research outputs found

    Developments and trends in three-dimensional mesh generation

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    An intense research effort over the last few years has produced several competing and apparently diverse methods for generating meshes. Recent progress is reviewed and the central themes are emphasized which form a solid foundation for future developments in mesh generation

    Aspects of Unstructured Grids and Finite-Volume Solvers for the Euler and Navier-Stokes Equations

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    One of the major achievements in engineering science has been the development of computer algorithms for solving nonlinear differential equations such as the Navier-Stokes equations. In the past, limited computer resources have motivated the development of efficient numerical schemes in computational fluid dynamics (CFD) utilizing structured meshes. The use of structured meshes greatly simplifies the implementation of CFD algorithms on conventional computers. Unstructured grids on the other hand offer an alternative to modeling complex geometries. Unstructured meshes have irregular connectivity and usually contain combinations of triangles, quadrilaterals, tetrahedra, and hexahedra. The generation and use of unstructured grids poses new challenges in CFD. The purpose of this note is to present recent developments in the unstructured grid generation and flow solution technology

    A new functional for improving cell area distribution

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    In this work we present a new area functional that help us improve the cell area distribution in structured grids over plane irregular regions, which avoids very small and very large cell areas as much as possible. We present some results and an implementation of this functional in a preliminary version of the latest UNAMalla system

    Automatic Generation of Near-Body Structured Grids

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    Numerical grid generation has been a bottleneck in the computational fluid dynamics process for a long time when using the structured overset grids. Many current structured overset grid generation schemes like the hyperbolic grid generation method require significant user interaction to generate good computational grids robustly. Other grid generation schemes like the elliptic grid generation method take a significant amount of time for grid calculation, which is not desirable for computational fluid dynamics. Herein a new grid generation method is presented that combines the hyperbolic grid generation scheme with the elliptic grid generation scheme that uses Poisson’s equation. The new scheme builds upon the strengths of the different techniques by first applying hyperbolic grid generation, which is very fast but sometimes fails in strong concavities, and then using elliptic grid generation to locally fix the problems where hyperbolic grid generation results are not acceptable for computational fluid dynamics calculation. The new technique is demonstrated in various examples that are known to cause problems for either hyperbolic or elliptic grid generation when applied alone. The computational speed of the combined scheme grid generation is also exanimated by comparing the results with hyperbolic and elliptic grid generation. The combined grid generation scheme is further implemented in Engineering Sketch Pad to get useful near-body structure grids based on the geometry of the model. Attributes in Engineering Sketch Pad are used to define the places where the surface and volume grids should be generated, while the tessellations are used to locate and project grid generation results and therefore boost grid generation speed. Three cases are tested to illustrate the implementation of the combined grid generation scheme in Engineering Sketch Pad

    Numerical computation of complex multi-body Navier-Stokes flows with applications for the integrated Space Shuttle launch vehicle

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    An enhanced grid system for the Space Shuttle Orbiter was built by integrating CAD definitions from several sources and then generating the surface and volume grids. The new grid system contains geometric components not modeled previously plus significant enhancements on geometry that has been modeled in the old grid system. The new orbiter grids were then integrated with new grids for the rest of the launch vehicle. Enhancements were made to the hyperbolic grid generator HYPGEN and new tools for grid projection, manipulation, and modification, Cartesian box grid and far field grid generation and post-processing of flow solver data were developed

    An Implicit Modified Lax-Wendroff Scheme for Irregular 2D Space Regions

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    Nowadays, there are many modelling problems which involve the shallow water equations for irregular domains. One of the most important blocks for solving these equations is the advection equation. In this paper, we present the implementation of an implicit modified Lax-Wendroff scheme in order to approximate the solution of the advection equation in some irregular domains in the plane, using a general finite difference method on structured convex grids
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