Adam Gaither - Academia.edu (original) (raw)

Papers by Adam Gaither

This paper presents an efficient block detection algorithm that can convert a complex wire frame ... more This paper presents an efficient block detection algorithm that can convert a complex wire frame geometry into a set of oriented multi--block structured faces or blocks. The algorithm uses a recursive depth first search in conjunction with the Grid Topology Model (GTM) data structure. The GTM data structure is a Boundary Representation (B--Rep) radial edge non--manifold solid modeling data structure. The block detection algorithm abstracts the user from having to manually specify orientation and connectivity information traditionally needed in other grid generation systems. Introduction A multi--block structured grid has multiple regions (blocks) within a single geometry that have their own corresponding local orientation and coordinate system. Each block may match other blocks at their end vertices, or be composed of composite elements that allow partial face matching. For clarity and brevity, only full face matched blocks will be considered in this paper. In two dimensions (2D), a...

The purpose of this thesis is to develop a topology data structure that supports both structured ... more The purpose of this thesis is to develop a topology data structure that supports both structured and unstructured grid generation methods. This topology data structure directly supports the method of building edge grids, surface grids and volume grids in order to construct high quality computational fluid dynamics (CFD) grids. The minimal topological information needed for computing both structured and unstructured grids is used to determine that a non manifold boundary representation topology data structure must be used. A search of published data structures led to the adoption of the radial edge non manifold (RENM) boundary representation data structure as the basis for our implementation. An explanation of the data structure details as well as behavior of the data structures is presented. The grid topology modelling (GTM) data structure has been implemented and is used in two different production grid generation systems, SolidMesh and GUM B. Several examples of high quality CFD g...

In this paper, a sequential 2D unstructured grid generator based on iterative point insertion and... more In this paper, a sequential 2D unstructured grid generator based on iterative point insertion and local reconnection is coupled with a Delauney tessellation domain decomposition scheme to create a scalable parallel unstructured grid generator. The Message Passing Interface (MPI) is used for distributed communication in the parallel grid generator. This work attempts to provide a generic framework to enable the parallelization of fast sequential unstructured grid generators in order to compute grand-challenge scale grids for Computational Field Simulation (CFS). Motivation for moving from sequential to scalable parallel grid generation is presented. Delaunay tessellation and iterative point insertion and local reconnection (advancing front method only) unstructured grid generation techniques are discussed with emphasis on how these techniques can be utilized for parallel unstructured grid generation. Domain decomposition techniques are discussed for both Delauney and advancing front ...

Author(s): Remotigue, M. G.; Gaither, A.; Hamann, Bernd; Jean, B. A.; Mastin, C. W.; Parmley, K. ... more Author(s): Remotigue, M. G.; Gaither, A.; Hamann, Bernd; Jean, B. A.; Mastin, C. W.; Parmley, K. P.; Soni, B. K.; Thompson, J. F.; Vaughan, P. | Editor(s): Weatherill, N. P.; Eisemann, P.; Haeuser, J.; Thompson, J. F. | Abstract: The National Grid Project has been under development at the NSF Engineering Research Center at Mississippi State University since 1991. A summary of the progress to date is presented. The project utilizes Non-Uniform Rational B-Splines (NURBS) for the geometry with a solid modeling Boundary Representation (B-Rep) data structure to represent topology. Geometry can be imported into the system via the Initial Graphics Exchange Specification (IGES), discrete XYZ's (interpolated into NURBS), or can be internally created by CAD operations. The NURBS are used parametrically both the structured and unstructured grid generation. Volumetric structured and unstructured grids are generated, visualized, and evaluated within the program, allowing the user the flexibi...

This paper presents an efficient block detection algorithm that can convert a complex wire frame ... more This paper presents an efficient block detection algorithm that can convert a complex wire frame geometry into a set of oriented multi–block structured faces or blocks. The algorithm uses a recursive depth first search in conjunction with the Grid Topology Model (GTM) data structure. The GTM data structure is a Boundary Representation (B–Rep) radial edge non–manifold solid modeling data structure. The block detection algorithm abstracts the user from having to manually specify orientation and connectivity information traditionally needed in other grid generation systems. Introduction A multi–block structured grid has multiple regions (blocks) within a single geometry that have their own corresponding local orientation and coordinate system. Each block may match other blocks at their end vertices, or be composed of composite elements that allow partial face matching. For clarity and brevity, only full face matched blocks will be considered in this paper. In two dimensions (2D), a cyc...

The National Grid Project (NGP) is a comprehensive numerical grid generation software system that... more The National Grid Project (NGP) is a comprehensive numerical grid generation software system that is being developed at the National Science Foundation (NSF) Engineering Research Center (ERC) for Computational Field Simulation (CFS) at Mississippi State University (MSU). NGP is supported by a coalition of U.S. industries and federal laboratories. The objective of the NGP is to significantly decrease the amount of time it takes to generate a numerical grid for complex geometries and to increase the quality of these grids to enable computational field simulations for applications in industry. A geometric configuration can be discretized into grids (or meshes) that have two fundamental forms: structured and unstructured. Structured grids are formed by intersecting curvilinear coordinate lines and are composed of quadrilateral (2D) and hexahedral (3D) logically rectangular cells. The connectivity of a structured grid provides for trivial identification of neighboring points by increment...

A procedure is presented for efficient generation of high-quality unstructured grids suitable for... more A procedure is presented for efficient generation of high-quality unstructured grids suitable for CFD simulation of high Reynolds number viscous flow fields. Layers of anisotropic elements are generated by advancing along prescribed normals from solid boundaries. The points are generated such that either pentahedral or tetrahedral elements with an implied connectivity can be be directly recovered. As points are generated they are temporarily attached to a volume triangulation of the boundary points. This triangulation allows efficient local search algorithms to be used when checking merging layers, The existing advancing-front/local-reconnection procedure is used to generate isotropic elements outside of the anisotropic region. Results are presented for a variety of applications. The results demonstrate that high-quality anisotropic unstructured grids can be efficiently and consistently generated for complex configurations.

37th Aerospace Sciences Meeting and Exhibit, Jan 11, 1999

A multiblock unstructured grid approach is presented for solving three-dimensional incompressible... more A multiblock unstructured grid approach is presented for solving three-dimensional incompressible inviscid and viscous turbulent flows about complete configurations. The artificial compressibility form of the governing equations is solved by a node-based, finite volume implicit scheme which uses a backward Euler time discretization. Point Gauss-Seidel relaxations are used to solve the linear system of equations at each time step. This work employs a multiblock strategy to the solution procedure, which greatly improves the efficiency of the algorithm by significantly reducing the memory requirements by a factor of 5 over the singlegrid algorithm while maintaining a similar convergence behavior. The numerical accuracy of solutions is assessed by comparing with the experimental data for a submarine with stern appendages and a high-lift configuration.

In this paper, a sequential 2D unstructured grid generator based on iterative point insertion and... more In this paper, a sequential 2D unstructured grid generator based on iterative point insertion and local reconnection is coupled with a Delauney tessellation domain decomposition scheme to create a scalable parallel unstructured grid generator . The Message Passing In- terface (MPI) is used for distributed communication in the parallel grid generator . This work attempts to provide a generic framework to enable the parallelization of fast sequen - tial unstructured grid generators in order to compute grand-challenge scale grids for Com- putational Field Simulation (CFS). Motivation for moving from sequential to scalable par - allel grid generation is presented. Delaunay tessellation and iterative point insertion and local reconnection (advancing front method only) unstructured grid generation techniques are discussed with emphasis on how these techniques can be utilized for parallel unstruc - tured grid generation. Domain decomposition techniques are discussed for both Delauney and advancing front unstructured grid generation with emphasis placed on the dif ferences needed for both grid quality and algorithmic ef ficiency.

Computational Aerosciences in the 21st Century, 2000

Unstructured grid technology has the potential to significantly reduce the overall user and CPU t... more Unstructured grid technology has the potential to significantly reduce the overall user and CPU time required for CFD analysis of realistic configurations. To realize this potential, improvements in automation, anisotropic generation, adaptation, and integration within the solution process are needed. Unstructured grid generation has advanced to the point where generation of a grid for most any configuration requires only a couple of hours of user time. However, prior to grid generation, the CAD geometry must be prepared. This process can take anywhere from hours to weeks. It is the single most labor-intensive task in the overall simulation process. Adherence to standards and alternative procedures for surface grid generation which account for small gaps and overlaps and generate across multiple surfaces can minimize and potentially eliminate much of the geometry preparation. With improvements in the geometry preparation process the overall grid generation task can be more fully automated. Anisotropic grid generation is another area in need of improvement. Current techniques have not advanced to the level of robustness and generality as for isotropic grid generation. Methodologies such as use of multiple normals or truly unstructured placement of anisotropic points need to be developed into more robust procedures. Also, solution-adaptation is a potential advantage of an unstructured grid approach that has not been developed into a feasible technology for high-resolution three-dimensional simulations.

Lecture Notes in Physics, 1995

The paper highlights some new work and trends related to unstructured grid generation and flow si... more The paper highlights some new work and trends related to unstructured grid generation and flow simulation. The generation of unstructured grids using iterative point insertion routines is discussed and it is shown that a general class of methods, of which one is the Delaunay triangulation, can be developed to give high quality grids. A framework is presented for the easy implementation of these methods into a parallel computer environment which significantly improves computational performance. Finally, the issue of the generation of grids suitable for viscous flows is discussed and results presented for high Reynolds number flows.

International Meshing Roundtable, 1999

A grid generation paradigm is presented that allows a user to build both structuredand unstructur... more A grid generation paradigm is presented that allows a user to build both structuredand unstructured grids within the same environment. It provides the user with aflexible, efficient and accurate way to generate these grids. The paradigm utilizes aBoundary Representation (B-rep) radial edge non-manifold solid modeling topologydata structure for all geometric and grid interrogations. Non-Uniform Rational BSplines(NURBS) are utilized as the

In this paper, a sequential 2D unstructured grid generator based on iterative point insertion and... more In this paper, a sequential 2D unstructured grid generator based on iterative point insertion and local reconnection is coupled with a Delauney tessellation domain decomposition scheme to create a scalable parallel unstructured grid generator . The Message Passing In- terface (MPI) is used for distributed communication in the parallel grid generator . This work attempts to provide a generic framework to enable the parallelization of fast sequen - tial unstructured grid generators in order to compute grand-challenge scale grids for Com- putational Field Simulation (CFS). Motivation for moving from sequential to scalable par - allel grid generation is presented. Delaunay tessellation and iterative point insertion and local reconnection (advancing front method only) unstructured grid generation techniques are discussed with emphasis on how these techniques can be utilized for parallel unstruc - tured grid generation. Domain decomposition techniques are discussed for both Delauney and a...

Computer-Aided Design, 2001

22nd ONR Symposium …, 1998

A perspective of computational hydrodynamics is presented that is considered relevant to particul... more A perspective of computational hydrodynamics is presented that is considered relevant to particular Naval hydrodynamic problems. This is not intended as a survey of the field in general; rather, it is a summary of the ongoing research and development of computational tools in the Computational Fluid Dynamics Lab at Mississippi State University. A discussion is given of the enabling technologies on which most of the computational tools are based. Example results are presented for submarines, surface ships, and propulsors, that attempt to illustrate the current status of certain Naval hydrodynamic computational capabilities. Some observations and comments are offered relating to various needs and possible directions of future computational hydrodynamic research and development.

This paper presents an efficient block detection algorithm that can convert a complex wire frame ... more This paper presents an efficient block detection algorithm that can convert a complex wire frame geometry into a set of oriented multi–block structured faces or blocks. The algorithm uses a recursive depth first search in conjunction with the Grid Topology Model (GTM) data structure. The GTM data structure is a Boundary Representation (B–Rep) radial edge non–manifold solid modeling data structure. The block detection algorithm abstracts the user from having to manually specify orientation and connectivity information traditionally needed in other grid generation systems. Introduction A multi–block structured grid has multiple regions (blocks) within a single geometry that have their own corresponding local orientation and coordinate system. Each block may match other blocks at their end vertices, or be composed of composite elements that allow partial face matching. For clarity and brevity, only full face matched blocks will be considered in this paper. In two dimensions (2D), a cyc...

37th Aerospace Sciences Meeting and Exhibit, Jan 11, 1999

In this paper, a sequential 2D unstructured grid generator based on iterative point insertion and... more In this paper, a sequential 2D unstructured grid generator based on iterative point insertion and local reconnection is coupled with a Delauney tessellation domain decomposition scheme to create a scalable parallel unstructured grid generator . The Message Passing In- terface (MPI) is used for distributed communication in the parallel grid generator . This work attempts to provide a generic framework to enable the parallelization of fast sequen - tial unstructured grid generators in order to compute grand-challenge scale grids for Com- putational Field Simulation (CFS). Motivation for moving from sequential to scalable par - allel grid generation is presented. Delaunay tessellation and iterative point insertion and local reconnection (advancing front method only) unstructured grid generation techniques are discussed with emphasis on how these techniques can be utilized for parallel unstruc - tured grid generation. Domain decomposition techniques are discussed for both Delauney and advancing front unstructured grid generation with emphasis placed on the dif ferences needed for both grid quality and algorithmic ef ficiency.

Computational Aerosciences in the 21st Century, 2000

Lecture Notes in Physics, 1995

International Meshing Roundtable, 1999

In this paper, a sequential 2D unstructured grid generator based on iterative point insertion and... more In this paper, a sequential 2D unstructured grid generator based on iterative point insertion and local reconnection is coupled with a Delauney tessellation domain decomposition scheme to create a scalable parallel unstructured grid generator . The Message Passing In- terface (MPI) is used for distributed communication in the parallel grid generator . This work attempts to provide a generic framework to enable the parallelization of fast sequen - tial unstructured grid generators in order to compute grand-challenge scale grids for Com- putational Field Simulation (CFS). Motivation for moving from sequential to scalable par - allel grid generation is presented. Delaunay tessellation and iterative point insertion and local reconnection (advancing front method only) unstructured grid generation techniques are discussed with emphasis on how these techniques can be utilized for parallel unstruc - tured grid generation. Domain decomposition techniques are discussed for both Delauney and a...

Computer-Aided Design, 2001

22nd ONR Symposium …, 1998