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Incompressible Compressible coupling...

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Old   June 17, 2009, 17:02
Post Incompressible Compressible coupling...
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Debojyoti Ghosh
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Hi,

Does anyone know of any paper dealing with the coupling of compressible and incompressible flow solver coupling?

-Debo
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Old   June 18, 2009, 02:24
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andy
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Coupling of what form? - separate butting solution regions?

What is the purpose of the coupling? - why not use an incompressible or compressible solver for the whole field?
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Old   June 18, 2009, 15:19
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Debojyoti Ghosh
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the idea is to have a compressible flow solver around a wing/blade and immerse that in a background (much larger) mesh on which incompressible solver works... The main flow is pretty low speed so it is incompressible but the flow near the wing itself is compressible...
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Old   June 18, 2009, 18:51
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There are two ways in which this can be done. Extending the incompressible solver to include the compressible regimes. Preconditioning of the compressible solvers to solve incompressible regime. Search for all mach number solvers and you will find many ways of performing such simulations using both the approaches.
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Old   June 19, 2009, 03:50
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Quote:
Originally Posted by dog5011 View Post
the idea is to have a compressible flow solver around a wing/blade and immerse that in a background (much larger) mesh on which incompressible solver works... The main flow is pretty low speed so it is incompressible but the flow near the wing itself is compressible...
I am not sure I can see the advantages in this compared to using a compressible solver adapted to handle low Mach number flows which can be done in a number of ways.

If you do attempt to butt an incompressible solver to a compressible solver in a low Mach number region you are likely to have significant problems with acoustic waves. The assumption of incompressibility cannot represent these and so a straightforward approach is going to reflect most of this energy at the interface. Unfortunately, at low Mach numbers, it is primarily the presence of acoustics waves that causes compressible solvers problems (hence the introduction of the assumption of incompressibility). A common way to tackle issues like this are buffer zones where you solve a modified form of the governing equations to progressively damp down whatever you are trying to remove.
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