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Old   January 27, 2011, 02:33
Question __Backward Facing Step simulation problems__
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Dear Foamers,
I have simulated backward facing step with LES model.
i created geometry with 200,000 grid. it is 3D with cyclic B.C for front and back walls. inlet conditions (U and k) are set same as Driver & Seegmiller paper. outlet pressure is set zero.
I don't understand why:

1- Minimum pressure is -278 m2/s2. as you know it means -278000Pa. it is -2.78 Bar but it is not real to have less than -1 Bar.

2- Reattachment point should be near x=6H which H is step height. but it is more than 11 H in this simulation. what is the problem?

Attachments are P and U contours.
Thanks in advance,
Attached Images
File Type: jpg P.jpg (20.0 KB, 30 views)
File Type: jpg Umean.jpg (22.2 KB, 29 views)
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Old   January 30, 2011, 10:48
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I want validate OpenFOAM with this test case. but it doesn't lead to success. i've ran it with kEpsilon, LRR and LES and their results are not acceptable.

Anyone know about this validation(BFS)?
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Old   February 11, 2011, 15:20
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inlet velocity turbulence was 0% in above snapshots. i changed it to 10%. So reattachment point becomes 8.5H instead of before 11H. H is step height. In Driver & Seegmiller reattachment should be 6H. i used LRR.
Changing inlet turbulent doesn't lead to desired one.
What should be changed?
Any help will be appreciated.
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