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Hyperbolic systems of equations posed on erroneous curved domains
Linköping University, Department of Mathematics, Computational Mathematics. Linköping University, Faculty of Science & Engineering.ORCID iD: 0000-0002-7972-6183
Linköping University, Department of Mathematics, Computational Mathematics. Linköping University, Faculty of Science & Engineering.
2016 (English)In: Journal of Computational Physics, ISSN 0021-9991, E-ISSN 1090-2716, Vol. 308, 438-442 p.Article in journal (Refereed) Published
Abstract [en]

The effect of an inaccurate geometry description on the solution accuracy of a hyperbolic problem is discussed. The inaccurate geometry can for example come from an imperfect CAD system, a faulty mesh generator, bad measurements or simply a misconception.

We show that inaccurate geometry descriptions might lead to the wrong wave speeds, a misplacement of the boundary conditions, to the wrong boundary operator and a mismatch of boundary data.

The errors caused by an inaccurate geometry description may affect the solution more than the accuracy of the specific discretization techniques used. In extreme cases, the order of accuracy goes to zero. Numerical experiments corroborate the theoretical results.

Place, publisher, year, edition, pages
Elsevier, 2016. Vol. 308, 438-442 p.
Keyword [en]
Hyperbolic systems; Erroneous curved domains; Inaccurate data; Convergence rate
National Category
URN: urn:nbn:se:liu:diva-123918DOI: 10.1016/ 000369086700021OAI: diva2:893780
Available from: 2016-01-13 Created: 2016-01-13 Last updated: 2016-08-31Bibliographically approved
In thesis
1. Stable High Order Finite Difference Methods for Wave Propagation and Flow Problems on Deforming Domains
Open this publication in new window or tab >>Stable High Order Finite Difference Methods for Wave Propagation and Flow Problems on Deforming Domains
2016 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

We construct stable, accurate and efficient numerical schemes for wave propagation and flow problems posed on spatial geometries that are moving, deforming, erroneously described or non-simply connected. The schemes are on Summation-by-Parts (SBP) form, combined with the Simultaneous Approximation Term (SAT) technique for imposing initial and boundary conditions. The main analytical tool is the energy method, by which well-posedness, stability and conservation are investigated. To handle the deforming domains, time-dependent coordinate transformations are used to map the problem to fixed geometries.

The discretization is performed in such a way that the Numerical Geometric Conservation Law (NGCL) is satisfied. Additionally, even though the schemes are constructed on fixed domains, time-dependent penalty formulations are necessary, due to the originally moving boundaries. We show how to satisfy the NGCL and present an automatic formulation for the penalty operators, such that the correct number of boundary conditions are imposed, when and where required.

For problems posed on erroneously described geometries, we investigate how the accuracy of the solution is affected. It is shown that the inaccurate geometry descriptions may lead to wrong wave speeds, a misplacement of the boundary condition, the wrong boundary operator or a mismatch of data. Next, the SBP-SAT technique is extended to time-dependent coupling procedures for deforming interfaces in hyperbolic problems. We prove conservation and stability and show how to formulate the penalty operators such that the coupling procedure is automatically adjusted to the variations of the interface location while the NGCL is preserved.

Moreover, dual consistent SBP-SAT schemes for the linearized incompressible Navier-Stokes equations posed on deforming domains are investigated. To simplify the derivations of the dual problem and incorporate the motions of the boundaries, the second order formulation is reduced to first order and the problem is transformed to a fixed domain. We prove energy stability and dual consistency. It is shown that the solution as well as the divergence of the solution converge with the design order of accuracy, and that functionals of the solution are superconverging.

Finally, initial boundary value problems posed on non-simply connected spatial domains are investigated. The new formulation increases the accuracy of the scheme by minimizing the use of multi-block couplings. In order to show stability, the spectrum of the semi-discrete SBP-SAT formulation is studied. We show that the eigenvalues have the correct sign, which implies stability, in combination with the SBP-SAT technique in time.

Place, publisher, year, edition, pages
Linköping: Linköping University Electronic Press, 2016. 23 p.
Linköping Studies in Science and Technology. Dissertations, ISSN 0345-7524 ; 1774
National Category
Computational Mathematics Mathematical Analysis Fluid Mechanics and Acoustics
urn:nbn:se:liu:diva-130928 (URN)10.3384/diss.diva-130928 (DOI)9789176857373 (Print) (ISBN)
Public defence
2016-09-30, Visionen, Hus B, Campus Valla, Linköping, 13:15 (English)
Available from: 2016-08-31 Created: 2016-08-31 Last updated: 2016-09-01Bibliographically approved

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