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Old   December 11, 2014, 07:34
Default Solving after mapping results
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Simone
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Hello everybody,

I know that this argument has been already discussed, but I can't find the answer I'm searching for.
I think the problem is general so it will probably be very interesting.

I run a steady-state RANS simulation (simpleFoam) and I mapped the results on a sub-domain with a finer mesh in order to run a transient DES simulation (pimpleFoam).

The question is: after I mapped the results on the sub-domain, how can I run the new simulation? I mean, which are the BC types I need to put on the boundary of the sub-domain?

Thanks for the answers,

Simone
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Old   December 11, 2014, 08:13
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Bobi
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Greetings Simone

You need to change some files in your start time for DES simulation. Sine your k file in RAS is different from k file in DES (incompressible LES case). k in RAS refers to turbulent intensity and in LES cases refers to subgrid scale kinetic energy. The order of magnitude of these values are completely different.
Moreover, you need to apply some changes in your U file. The values obtained from RAS simulation are your mean values \overline U, you need to define fluctuation scale and values.

Your velocity B.C. for inflow streams should be sth like this:

Code:
FUEL
    {
        type            turbulentInlet;
        referenceField  nonuniform List<vector>
252
(
(-0.296506256 142.798641 0.146544894)


);

    fluctuationScale (0.03 0.1 0.03);    //Define the highest value in the stream orientation
    value uniform (0 0 0)   
}
Best,

Bobi
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Old   December 11, 2014, 09:01
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Simone
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Thanks for the reply!

I explain you more in details.
I did a similar simulation with CFD++ and I wanted to know if it is possible even with OF.
I studied the aeroacoustics of a car using CFD++. Firstly I run a RANS simulation in the whole domain and then I used the obtained results to initialize a transient DES simulation only on a sub-domain near the car-mirror. To do this I put as BC on the whole external sud-domain boundary a particular condition, called NLAS outer boundary.

I don't know where the inlet and the outlet are in the sub-domain. Probably the most matching BC is to consider all the boundary as an opening.
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Old   December 11, 2014, 09:24
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Bobi
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Greetings Simone

Your case is not actually my type. However, I think you should have an outlet for your air stream traversing beside the car mirror. I don't think that you could define inflow streams in your case without defining any outflow.

Best,
Bobi
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Old   December 11, 2014, 09:27
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Simone
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Ok, I'll try as you previously suggested.

Thanks,

Simone
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