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Epsilon and mixing length value for airfoil simulation |
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January 29, 2009, 07:50 |
Hi all,
I'm trying to simulat
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#1 |
New Member
Gianluca VZ
Join Date: Mar 2009
Posts: 6
Rep Power: 17 |
Hi all,
I'm trying to simulate a turbulent flow around an airfoil. I have some difficulties in evaluating the correct value for epsilon. In particular I don't know which value of the mixing length I should use. The domain is 3 meters long and 2 high. The airfoil is located at 1 meter from the inlet and in the middle of the height, the chord length is 0.1 m, the speed is 100 m/s, Re=1e6. Thank you in advance for your suggestions. Bye Gianluca |
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January 29, 2009, 09:33 |
Hi, this is what I obtained so
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#2 |
New Member
Gianluca VZ
Join Date: Mar 2009
Posts: 6
Rep Power: 17 |
Hi, this is what I obtained so far.
I attach the directory of the case and a screenshot. Thanks again. airfoil_simulation.zip Gianluca |
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January 29, 2009, 12:32 |
hi,
your U value seams to b
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#3 |
Senior Member
Wolfgang Heydlauff
Join Date: Mar 2009
Location: Germany
Posts: 136
Rep Power: 21 |
hi,
your U value seams to be 10m/s instead of 100. you also will have to raise the size of your mesh to 40-100 times the chordlength. |
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January 29, 2009, 15:17 |
Actually, Gianluca and I tried
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#4 |
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antonio segalini
Join Date: Mar 2009
Posts: 75
Rep Power: 17 |
Actually, Gianluca and I tried to do a different simulation with the k and epsilon of a simulation of prof.Jasak on a naca 0012. with the same chord length and the same distance. but you see the result (it is embarassing :-) )
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January 30, 2009, 17:32 |
Hello Antonio and Gianluca,
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#5 |
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Maruthamuthu Venkatraman
Join Date: Mar 2009
Location: Norway
Posts: 80
Rep Power: 17 |
Hello Antonio and Gianluca,
Try to keep y+ approx 1 to 5 and use sst k-w model. You shall check the best practise guidelines in ERCOFTAC for such flow. Naca profile example is there in it... May be it helps you. good luck |
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January 31, 2009, 14:15 |
Mmmm,
the k-Omega SST coded
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#6 |
Senior Member
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Mmmm,
the k-Omega SST coded in OF is based on a wall functions approach, so it should be necessary to use an y+ of about 30... egards, Ivan |
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February 1, 2009, 04:55 |
thanks Ivan and Maruthamuthu.
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#7 |
Member
antonio segalini
Join Date: Mar 2009
Posts: 75
Rep Power: 17 |
thanks Ivan and Maruthamuthu. We find out our bug :-). In the boundary file we did not specify that the profile surface was of wall type. There are other types in OpenFOAM (inlet, outlet, etc...)
Is it so important to specify the other types (apart wall of course)? |
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