Change search
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
Acceleration of Compressible Flow Simulations with Edge using Implicit Time Stepping
KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Aerodynamics.ORCID iD: 0000-0001-9902-6216
2012 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

Computational fluid dynamics (CFD) has become a significant tool routinely used in design and optimization in aerospace industry. Typical flows may be characterized by high-speed and compressible flow features and, in many cases, by massive flow separation and unsteadiness. Accurate and efficient numerical solution of time-dependent problems is hence required, and the efficiency of standard dual-time stepping methods used for unsteady flows in many CFD codes has been found inadequate for large-scale industrial problems. This has motivated the present work, in which major effort is made to replace the explicit relaxation methods with implicit time integration schemes. The CFD flow solver considered in this work is Edge, a node-based solver for unstructured grids based on a dual, edge-based formulation. Edge is the Swedish national CFD tool for computing compressible flow, used at the Swedish aircraft manufacturer SAAB, and developed at FOI, lately in collaboration with external national and international partners. The work is initially devoted to the implementation of an implicit Lower-Upper Symmetric Gauss-Seidel (LU-SGS) type of relaxation in Edge with the purpose to speed up the convergence to steady state. The convergence of LU-SGS has been firstly accelerated by basing the implicit operator on a flux splitting method of matrix dissipation type. An increase of the diagonal dominance of the system matrix was the principal motivation. Then the code has been optimized by means of performance tools Intel Vtune and CrayPAT, improving the run time. It was found that the ordering of the unknowns significantly influences the convergence. Thus, different ordering techniques have been investigated. Finding the optimal ordering method is a very hard problem and the results obtained are mostly illustrative. Finally, to improve convergence speed on the stretched computational grids used for boundary layers LU-SGS has been combined with the line-implicit method.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2012. , x, 35 p.
Series
Trita-AVE, ISSN 1651-7660 ; 2012:25
Keyword [en]
compressible CFD, convergence acceleration, implicit time-stepping, matrix dissipation, line-implicit, performance optimization
National Category
Engineering and Technology Aerospace Engineering
Identifiers
URN: urn:nbn:se:kth:diva-97455OAI: oai:DiVA.org:kth-97455DiVA: diva2:533381
Presentation
2012-06-11, Entrepl (E2), Lindstedsvägen 3, KTH, Stockholm, 10:15 (English)
Opponent
Supervisors
Note
QC 20120626Available from: 2012-06-26 Created: 2012-06-13 Last updated: 2012-06-26Bibliographically approved
List of papers
1. Convergence Acceleration of the CFD Code Edge by LU-SGS
Open this publication in new window or tab >>Convergence Acceleration of the CFD Code Edge by LU-SGS
2011 (English)In: 3rd CEAS European Air & Space Conference, Venice, 24-28 October 2011, CEAS/AIDAA , 2011, 606-611 p.Conference paper, Published paper (Refereed)
Abstract [en]

Edge is a flow solver for unstructured grids based on a dual grid and edge-based formulation. The standard dual-time stepping methods for compressible unsteady flows are inadequate for large-scale industrial problems. This has motivated the present work, in which an implicit Lower-Upper Symmetric Gauss-Seidel (LU-SGS) type of relaxation has been implemented in the code Edge with multigrid acceleration. Two different types of dissipation, a scalar and a matrix model, have been constructed which increase the diagonal dominance of the system matrix but not the numerical viscosity of the computed solution. A parametric study demonstrates convergence accelerations by a factor of three for inviscid transonic flows compared to explicit Runge-Kutta smoothing for multigrid acceleration.

Place, publisher, year, edition, pages
CEAS/AIDAA, 2011
Keyword
compressible CFD, convergence acceleration, implicit time-stepping, matrix dissipation
National Category
Aerospace Engineering
Identifiers
urn:nbn:se:kth:diva-78943 (URN)
Conference
3rd CEAS European Air & Space Conference
Note
QC 20120209Available from: 2012-02-09 Created: 2012-02-08 Last updated: 2014-12-01Bibliographically approved
2. Performance analysis of the LU-SGS algorithm in the CFD code Edge
Open this publication in new window or tab >>Performance analysis of the LU-SGS algorithm in the CFD code Edge
(English)Manuscript (preprint) (Other academic)
National Category
Aerospace Engineering
Identifiers
urn:nbn:se:kth:diva-98474 (URN)
Note
QS 2012Available from: 2012-06-26 Created: 2012-06-26 Last updated: 2012-06-26Bibliographically approved
3. Implementation of Implicit LU-SGS method with Line-implicit scheme on Stretched Unstructured Grids
Open this publication in new window or tab >>Implementation of Implicit LU-SGS method with Line-implicit scheme on Stretched Unstructured Grids
(English)Manuscript (preprint) (Other academic)
Abstract [en]

A first implementation of line-implicit Lower-Upper Symmetric Gauss-Seidel (LU-SGS) in Edge has been considered in this paper for convergenceacceleration on stretched meshes. The motivation comes from the lack of efficiency of the implicit LU-SGS when running in RANS meshes. Edge is a flow solver for unstructured grids based on a dual grid and edge-based formulation. The line-implicit method has been implemented in the code Edge has an acceleration method when computing explicit schemes in stretched meshes. This methods works only in regions of stretched grid where the flow equations are integrated implicitly in time along the structured lines. The combination with an implicit LU-SGS should remove the restriction of the time step for explicit schemes and accelerate the convergence to steady state. The results have shown that for highly stretched meshes, line-implicit LU-SGS could perform much faster than LU-SGS.

National Category
Aerospace Engineering
Identifiers
urn:nbn:se:kth:diva-98475 (URN)
Note
QS 2012Available from: 2012-06-26 Created: 2012-06-26 Last updated: 2012-06-26Bibliographically approved

Open Access in DiVA

errata(65 kB)61 downloads
File information
File name ERRATA01.pdfFile size 65 kBChecksum SHA-512
e9cc11f159531f6e21e15a75cfc55dbdcaf5919a7d7321ec0e3584d13e323e2a07e032b9543e930b06b8471839078bb01504598dee3de8002db1bfb868c24b0d
Type errataMimetype application/pdf
Licentiate_E-Otero(5575 kB)766 downloads
File information
File name FULLTEXT03.pdfFile size 5575 kBChecksum SHA-512
7eca9d0dfb4337dd59a7781bdd79dcded6af0e15996d2ccc5271f88cdf9b607ffe258a8ad570013b525224cb9e3657e4cd2d54721faffe5ec9d140f2210bb8d8
Type fulltextMimetype application/pdf

Authority records BETA

Otero, Evelyn

Search in DiVA

By author/editor
Otero, Evelyn
By organisation
Aerodynamics
Engineering and TechnologyAerospace Engineering

Search outside of DiVA

GoogleGoogle Scholar
Total: 766 downloads
The number of downloads is the sum of all downloads of full texts. It may include eg previous versions that are now no longer available

urn-nbn

Altmetric score

urn-nbn
Total: 299 hits
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf