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Hybrid Grid Generation for Viscous Flow Computations Around Complex Geometries
KTH, School of Engineering Sciences (SCI), Mechanics.
2009 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

A set of algorithms building a program package for the generation of twoandthree-dimensional unstructured/hybrid grids around complex geometrieshas been developed.

The unstructured part of the grid generator is based on the advancing frontalgorithm. Tetrahedra of variable size, as well as directionally stretched tetrahedracan be generated by specification of a proper background grid, initiallygenerated by a Delaunay algorithm.

A marching layer prismatic grid generation algorithm has been developedfor the generation of grids for viscous flows. The algorithm is able to handleregions of narrow gaps, as well as concave regions. The body surface is describedby a triangular unstructured surface grid. The subsequent grid layers in theprismatic grid are marched away from the body by an algebraic procedurecombined with an optimization procedure, resulting in a semi-structured gridof prismatic cells.

Adaptive computations using remeshing have been done with use of a gradientsensor. Several key-variables can be monitored simultaneously. The sensorindicates that only the key-variables with the largest gradients give a substantialcontribution to the sensor. The sensor gives directionally stretched grids.

An algorithm for the surface definition of curved surfaces using a biharmonicequation has been developed. This representation of the surface canbe used both for projection of the new surface nodes in h-refinement, and theinitial generation of the surface grid.

For unsteady flows an algorithm has been developed for the deformationof hybrid grids, based on the solution of the biharmonic equation for the deformationfield. The main advantage of the grid deformation algorithm is that itcan handle large deformations. It also produces a smooth deformation distributionfor cells which are very skewed or stretched. This is necessary in orderto handle the very thin cells in the prismatic layers.

The algorithms have been applied to complex three-dimensional geometries,and the influence of the grid quality on the accuracy for a finite volumeflow solver has been studied for some simpler generic geometries.

Place, publisher, year, edition, pages
Stockholm: KTH , 2009. , viii, 48 p.
Series
Trita-MEK, ISSN 0348-467X ; 2009:17
Keyword [en]
grid generation, unstructured grids, hybrid grids, surface grids, three-dimensional grids, adaptive grids, moving grids, grid quality, accuracy
National Category
Fluid Mechanics and Acoustics
Identifiers
URN: urn:nbn:se:kth:diva-11934ISBN: 978-91-7415-491-7 (print)OAI: oai:DiVA.org:kth-11934DiVA: diva2:290618
Public defence
2010-02-19, Sal F3, Lindstedtsvägen 26, KTH, Stockholm, 10:15 (English)
Opponent
Supervisors
Note
QC 20100812Available from: 2010-01-27 Created: 2010-01-27 Last updated: 2010-08-12Bibliographically approved
List of papers
1. Adaptive grid generation for 3D unstructured grids
Open this publication in new window or tab >>Adaptive grid generation for 3D unstructured grids
(English)Manuscript (preprint) (Other academic)
National Category
Fluid Mechanics and Acoustics
Identifiers
urn:nbn:se:kth:diva-24076 (URN)
Note
QC 20100812Available from: 2010-08-12 Created: 2010-08-12 Last updated: 2010-08-12Bibliographically approved
2. Hybrid grid generation for complex 3D geometries
Open this publication in new window or tab >>Hybrid grid generation for complex 3D geometries
(English)Manuscript (preprint) (Other academic)
National Category
Fluid Mechanics and Acoustics
Identifiers
urn:nbn:se:kth:diva-24078 (URN)
Note
QC 20100812Available from: 2010-08-12 Created: 2010-08-12 Last updated: 2010-08-12Bibliographically approved
3. Grid deformation of 3D hybrid grids
Open this publication in new window or tab >>Grid deformation of 3D hybrid grids
(English)Manuscript (preprint) (Other academic)
National Category
Mechanical Engineering
Identifiers
urn:nbn:se:kth:diva-24077 (URN)
Note
QC 20100812Available from: 2010-08-12 Created: 2010-08-12 Last updated: 2010-08-12Bibliographically approved
4. A higher order representation of unstructured surface grids
Open this publication in new window or tab >>A higher order representation of unstructured surface grids
(English)Manuscript (preprint) (Other academic)
National Category
Fluid Mechanics and Acoustics
Identifiers
urn:nbn:se:kth:diva-24080 (URN)
Note
QC 20100812Available from: 2010-08-12 Created: 2010-08-12 Last updated: 2010-08-12Bibliographically approved
5. Accuracy evaluation of the unstructured node- centered finite volume method in aerodynamic
Open this publication in new window or tab >>Accuracy evaluation of the unstructured node- centered finite volume method in aerodynamic
(English)Manuscript (preprint) (Other academic)
National Category
Fluid Mechanics and Acoustics
Identifiers
urn:nbn:se:kth:diva-24081 (URN)
Note
QC 20100812Available from: 2010-08-12 Created: 2010-08-12 Last updated: 2010-08-12Bibliographically approved
6. Experiences of grid generation and steady/unsteady viscous computations for complex geometries.
Open this publication in new window or tab >>Experiences of grid generation and steady/unsteady viscous computations for complex geometries.
(English)Manuscript (preprint) (Other academic)
National Category
Fluid Mechanics and Acoustics
Identifiers
urn:nbn:se:kth:diva-24082 (URN)
Note
QC 20100812Available from: 2010-08-12 Created: 2010-08-12 Last updated: 2010-08-12Bibliographically approved

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CiteExportLink to record
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Citation style
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Output format
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