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DNS of duct flow

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Old   June 17, 2014, 05:35
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Florian Ries
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Hi mgg,
me too

Concerning the accuracy please read this:
Quasi-DNS capabiltities of OpenFOAM for different mesh types. Ed Komen

very interessting

kind regards
Florian
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Old   June 17, 2014, 05:56
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Quote:
Originally Posted by itchy View Post
Hi mgg,
me too

Concerning the accuracy please read this:
Quasi-DNS capabiltities of OpenFOAM for different mesh types. Ed Komen

very interessting

kind regards
Florian
I have read it before. It is an interesting work! In my case, I always use structed mesh. I think for his Re, it is a huge mesh number, it that because of unstructed mesh? I am also curious about the scalability in his work.
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Old   June 17, 2014, 10:59
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Huang Xianbei
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Quote:
Originally Posted by mgg View Post
http://www.mcs.anl.gov/~fischer/nek5000/sprague_nek5000_dec2010.pdf

Is that helpful? I am using OpenFOAM for DNS pipe flow. I am also interested in this topic.
In fact, when applying 2nd-order schemes with FVM,the accuracy can be close to spectral method under low Re. Just as the document said,with Ret=180. When using the same mesh with DNS of spectral, the result is with significant deviation.
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Old   June 17, 2014, 16:09
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Florian Ries
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hi mgg,

not sure if structured or unstructed grid make a major difference.
In my pipe-flow simulation I used similar amount of cells (structured mesh). The problem is the numerical diffusivity. With OpenFOAM the numerical diffusivity is very high in my opinion, especially if the grid is "coarse" (if we can say coarse for DNS ).

I use only Gauss linear schemes, poorly 2nd order.

I will see next week the result of my DNS, then I can tell you more about accuracy of FVM DNS.

kind regards
Florian
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Old   July 11, 2014, 09:51
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Hi Florian,

long time no see. How does your results look?

regards,
mgg

Quote:
Originally Posted by itchy View Post
hi mgg,

not sure if structured or unstructed grid make a major difference.
In my pipe-flow simulation I used similar amount of cells (structured mesh). The problem is the numerical diffusivity. With OpenFOAM the numerical diffusivity is very high in my opinion, especially if the grid is "coarse" (if we can say coarse for DNS ).

I use only Gauss linear schemes, poorly 2nd order.

I will see next week the result of my DNS, then I can tell you more about accuracy of FVM DNS.

kind regards
Florian
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Old   November 29, 2014, 09:25
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Niu
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Hi andersn,
How about your DNS of duct flow? have you compared your results with other papers' results?
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Old   December 1, 2014, 02:20
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Jason Tan
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Originally Posted by andersn View Post
hello Niu
To my case,the flow direction I set as periodic boundary condition.As for the initial condition of p and U,I set it according http://www.cfd-online.com/Forums/ope...s-2-1-0-a.html using the tool perturbU.what kind of your case?Are you working on duct DNS also?

I have update my meshes.
Code:
Domain size:6.4X1X1
grid:60*80*80
distance between first grid to wall:  0.002
the  stretching ratio:1.06
but the result seems worse.

Can anyone give me some suggestion?

regards!

andersn
Hi,

What I'm doing now is duct flow. And I met some problems in it. I don't know how to use the perturbU to initial U fields, I think the block is the setting of perturbUDict. At present, all the perturbU files are about channel flow. Did you use the perturbU to initial your U fields?And How?
Best wishes.
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