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Implementation of k-Exact Finite Volume Reconstruction in DLR’s Next-Generation CFD Solver: Flucs and its Comparison to Other Methods
KTH, School of Engineering Sciences (SCI), Mechanics.
2017 (English)Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
Abstract [en]

This thesis extended the order of the reconstruction of state for convective fluxes used by Finite Volume (FV) algorithm in DLR’s next-generation CFD solver: Flucs, from constant and linear to quadratic and cubic. Two approaches for calculating derivatives were implemented in Flucs and some test cases were tried. To allow for integration of moments within each cell and a higher-order integration of fluxes, the mesh used by Discontinuous Galerkin (DG) was fed to the FV algorithm. Insufficient geometric treatment of the boundary cells and the dummy cells in FV is believed to be detrimental to the order of error reduction in NACA0012 case and the smooth bump case. In the smooth bump case, the FV algorithms failed to show higher than second order error reduction because of this reason. The order of the schemes away from the boundaries was verified with the Ehrenfried Vortex test case. For at least structured meshes and unstructured meshes with quads, schemes of order k approached k + 1 order accuracy on sufficiently fine meshes. The original goal of this thesis was partly accomplished and some further work in the code is expected.

Abstract [sv]

Detta examensarbete vidareutvecklade ordningen av rekonstruktion av tillståndet för konvektiva flöden som används av FV-algoritmen i DLR’s nästa generations CFD-lösare: Flucs, från konstant och linjär till kvadratisk och kubisk. Två metoder för beräkning av derivatorna genomfördes i Flucs och några testfall försökades. För att möjliggöra integrationen av momenten inom varje cell och integrationen av flöden på en högre ordning, matades det nät som används av DG till FV-algoritmen. Otillräcklig geometrisk behandling av gränscellerna och dummycellerna antas vara skadlig för ordning av felreduceringen i NACA0012-fallet och det Smmoth Bump-fallet. I det Smooth Bump-Fallet fick FV-algoritmerna inte visa högre än andra ordning av felreducering på grund av denna anledning. Ordningen av schemana bort från gränserna verifierades med Ehrenfried Vortex-testfallet. För åtminstone strukturerade nät och ostrukturerade nät med fyrkantiga celler nådde algorithmer med order k, k + 1 ordernoggrannhet på tillräckliga bra nät. Det ursprungliga målet för denna avhandling uppnåddes delvis och ytterligare arbete i koden förväntas.

Place, publisher, year, edition, pages
2017. , p. 33
National Category
Engineering and Technology
Identifiers
URN: urn:nbn:se:kth:diva-220315OAI: oai:DiVA.org:kth-220315DiVA, id: diva2:1167206
External cooperation
DLR
Supervisors
Examiners
Available from: 2017-12-18 Created: 2017-12-18 Last updated: 2017-12-18Bibliographically approved

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