Dynamic boundary conditions in computational fluid dynamics

Mario A. Storti*, Norberto M. Nigro, Rodrigo R. Paz, Lisandro Dalcin

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

20 Scopus citations

Abstract

The number and type of boundary conditions to be used in the numerical modeling of fluid mechanics problems is normally chosen according to a simplified analysis of the characteristics, and also from the experience of the modeler. The problem is harder at inflow/outflow boundaries which are, in most cases, artificial boundaries, so that a bad decision about the boundary conditions to be imposed may affect the precision and stability of the whole computation. For inviscid flows, the analysis of the sense of propagation in the normal direction to the boundaries gives the number of conditions to be imposed and, in addition, the conditions that are "absorbing" for the waves impinging normally to the boundary. In practice, it amounts to counting the number of positive and negative eigenvalues of the advective flux Jacobian projected onto the normal. The problem is even harder when the number of incoming characteristics varies during the computation, and the correct treatment of these cases poses both mathematical and practical problems. One example considered here is a compressible flow where the flow regime at a certain part of an inlet/outlet boundary can change from subsonic to supersonic and the flow can revert. In this work the technique for dynamically imposing the correct number of boundary conditions along the computation, using Lagrange multipliers and penalization, is discussed and several numerical examples are presented.

Original languageEnglish (US)
Pages (from-to)1219-1232
Number of pages14
JournalComputer Methods in Applied Mechanics and Engineering
Volume197
Issue number13-16
DOIs
StatePublished - Feb 15 2008

Keywords

  • Absorbing boundary conditions
  • Computational fluid dynamics
  • Finite elements

ASJC Scopus subject areas

  • Computational Mechanics
  • Mechanics of Materials
  • Mechanical Engineering
  • Physics and Astronomy(all)
  • Computer Science Applications

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