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Computational & Run Time requirements for CAA

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Old   June 16, 2010, 01:36
Default Computational & Run Time requirements for CAA
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Danillo Cafaldo dos Reis
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Hi,

I'm a undergraduate student and I'm about to start a CAA research in CFX. I've no previous experience in this area, so in order to write my project I need to know the computational and run time requirements for a simple geometry. How many nodes would I need for a LES method?
Please, any comment will be welcome.

Thanks
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Old   June 16, 2010, 08:22
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Glenn Horrocks
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It depends on what you are modelling, of course.

But any LES model will involve large meshes and long run times. LES is very computationally expensive.
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Old   June 16, 2010, 10:16
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Danillo Cafaldo dos Reis
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Thank you Glenn Horrocks for your answer.

My first idea is to model an airfoil-slat geometry, but I thing I won't have enough computational resource to explore this problem in CFX, mainly because its iterative solver. Maybe a CAA designed software should allow me to do this.

So in order to write my project I need to know what kind of geometry I will be able to explore in CFX.

Thanks
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Old   June 16, 2010, 10:21
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Basically in a LES simulation you try to represent directly the large scales and the effects of the small scales are modelled. The required grid spacing h is proportional to a specified filter width that should be smaller than the size of the smallest energy-containing motions. you can see an overview of all modeling approaches in Pope for example.

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Old   June 16, 2010, 18:38
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Glenn Horrocks
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Quote:
My first idea is to model an airfoil-slat geometry
What Re and Ma numbers?
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Old   June 17, 2010, 18:07
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Danillo Cafaldo dos Reis
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Re~9e6 e Ma=0.3
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Old   June 17, 2010, 19:40
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This is quite a high Re number, meaning that the turbulent structures will be quite small. On top of that you will have compressibility effects with Ma=0.3. This is definitely going to be a challenging model and will require a compute cluster of some size and lots of run time.
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Old   June 21, 2010, 19:01
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Danillo Cafaldo dos Reis
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Thank you Glenn Horrocks and Antonio for your answers.

I will change my initial idea and simulate a Mixing Layer, that can be interpreted as a very simplified model of slat.
I'm sure that this will be possible to do.

Best regards
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