A boundary representation solid modelling data structure for general numerical grid generation (original) (raw)

Topology Abstraction of Surface Models for Three-Dimensional Grid Generation

Engineering with Computers, 2001

Surface grid generation and the subsequent volume grid generation is the key to unstructured gridbased computational simulation. The baseline entities of the surface models under consideration for use with the proposed surface grid generator are curves and surfaces. There is a necessity to establish a topology relation between the curves and surfaces, prior to a surface gridding process. The present paper addresses issues related to this topology abstraction. Effort has also been made to generally discuss how to bridge the gap between CAD modelling and surface gridding. The proposed procedures have been incorporated into an Interactive Geometry Utility Environment (IGUE). The IGUE is a sub-environment of a Parallel Simulation User Environment (PSUE), which has been developed for unstructured grid-based computational simulation. Arbitrary computer application software can be integrated into the environment to provide a multidisciplinary engineering analysis capability within one unified computational framework. Examples of computational applications have been included in the present paper, to demonstrate the use of the PSUE and geometry preparation procedure with an emphasis of topology abstraction.

An automatic unstructured grid generation method for viscous flow simulations

High aspect-ratio grids are required for accurate solution of boundary layer and wake flow. An approach for the efficient generation of isotropic and stretched viscous unstructured grids is introduced in this paper. The proposed grid generation algorithm starts with a very coarse initial grid. In far field regions, isotropic cells of excellent quality are produced using a combination of point insertion and cell subdivision techniques. Simultaneously, a directional grid refinement strategy is used to construct highly stretched triangular cells in viscous dominated regions. First, anisotropic unstructured grids are produced in the stream-wise direction. Then, cells close to the solid surface are refined to highly stretched layer of triangles suitable for boundary layer region. The accuracy of the current grid generation approach is assessed by laminar and turbulent compressible flow solutions around NACA0012, RAE2822, and NHLP multi-element airfoils. Numerical flow simulation results are compared with published data. Comparisons point to accuracy of the proposed unstructured viscous grid generation procedure.

A numerical grid generation technique

Computers & Fluids, 1988

The paper describes a technique for the generation of boundary-fitted curvilinear coordinate systems for the numerical solution of partial differential equations in two space dimensions. The technique is algebraic, has a transfinite character, and is based on the blending of shearing transformations. Applications to numerical grid generation for problems in the field of computational fluid dynamics are presented.

Generation of block-structured grids in complex computational domains using templates

Finite Elements in Analysis and Design, 2003

In numerical analysis, the process of grid generation is used to decompose computational domains into ÿnite elements or ÿnite volumes. It is very di cult to generate quality grids for complex computational domains with a good distribution of nodes. This paper presents a concept for computational grid optimization performed by decomposing complex domains into simpler parts on a basis of a decomposition scheme ("template"). Complex boundaries are replaced by a number of simple patches. Special geometric constraints are imposed on the constituents of patches to allow for the same decomposition scheme to be used for a broad variety of boundary shapes. These constraints ensure consistency of the computational domain during positional and dimension changes of structural components. Grid generation is performed in four steps: building of a template, applying the template to particular data, optimization of the position of subvolume components and ÿnally, the grid generation inside subvolumes. We demonstrate our concept using an example of water turbine geometry and compare the quality of the generated numerical grids with respect to the orthogonality criteria. ?

A Cartesian-base unstructured grid generation method for moving boundary applications

A geometric adaptation method is presented for automatic generation of moving boundary unstructured grids. The method has extended the applicability of the existing Cartesian-base unstructured grid generation method to moving boundary applications. The grid generation procedure uses a Cartesian grid approach as a suitable ground for data structure access. In addition, the method requires minimum modification of the grid (and data structure) during the relative motion of the bodies, since the majority of the Cartesian cells are unchanged throughout the moving process. Therefore, less computations and higher accuracy can be achieved due to minimum grid modification and flow variable interpolation. To demonstrate the feasibility of this method, initial computations have been carried out for a store separation case using a cell-centered finite volume inviscid flow solver.

Hybrid Grid Generation for Viscous Flow Simulations in Complex Geometries

In this paper, we present a hybrid grid generation approach for viscous flow simulations by marching a surface triangulation on viscous walls along certain directions. Focuses are on the computing strategies used to determine the marching directions and distances since these strategies determine the quality of the resulting elements and the reliability of the meshing procedure to a large extent. With respect to marching direction, three strategies featured with different levels of efficiencies and robustness performance are combined to compute the initial normals at front nodes to balance the trade-off between efficiency and robustness. A novel weighted strategy is used in the normal smoothing scheme, which evidently reduce the possibility of early stop of front generation at complex corners. With respect to marching distances, the distance settings at concave and/or convex corners are locally adjusted to smooth the front shape at first; a further adjustment is then conducted for fr...

Domain Decomposition By the Advancing-Partition Method for Parallel Unstructured Grid Generation

47th AIAA Aerospace Sciences Meeting including The New Horizons Forum and Aerospace Exposition, 2009

A new method of domain decomposition has been developed for generating unstructured grids in subdomains either sequentially or using multiple computers in parallel. Domain decomposition is a crucial and challenging step for parallel grid generation. Prior methods are generally based on some auxiliary, complex, and computationally intensive operations for defining partition interfaces and usually produce grids of lower quality than those generated in single domains. The new technique, referred to as "Advancing Partition," is native to the underlying grid generation method by the Advancing-Front method and partitions a domain as part of the volume mesh generation in a "natural" way. The benefits of this approach are: 1) the process of domain decomposition is highly automated, 2) partitioning of domain does not compromise the quality of the generated grids, and 3) the computational overhead for domain decomposition is minimal. The new method has been implemented in NASA's unstructured grid generation code VGRID. 1,2