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May 3, 2012, 10:41 |
Add Random value to velocity
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#1 |
Senior Member
Jian Zhong
Join Date: Feb 2012
Location: Birmingham
Posts: 109
Rep Power: 14 |
Dear Foamers,
How to add random value to velocity in the solver using LES? I just want to see larger eddies in a shorter time? It may relate to Random.H function. But how to link it to velocity? I have no experience of using Random.H. |
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May 3, 2012, 14:18 |
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#2 | |
Assistant Moderator
Bernhard Gschaider
Join Date: Mar 2009
Posts: 4,225
Rep Power: 51 |
Quote:
Code:
Description Generate a fluctuating inlet condition by adding a random component to a reference (mean) field. Input: referenceField Mean field. fluctuationScale RMS fluctuation, provided as the fraction of the mean field. alpha temporal correlation factor; the fraction of the new random component added to the previous time-step (defaults to 0.1). |
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May 3, 2012, 16:50 |
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#3 |
Senior Member
Jian Zhong
Join Date: Feb 2012
Location: Birmingham
Posts: 109
Rep Power: 14 |
Thanks. But my BC is cyclic. I want to add a perturbation component to velocity vector. I noticed that perturbU utility can be useful. But I do not know how to do that.
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July 10, 2013, 17:21 |
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#4 |
Member
Negin Nazarian
Join Date: Jan 2012
Location: San Diego
Posts: 61
Rep Power: 14 |
Hi Jian,
I was wondering if you were able to introduce the perturbation and how?. I also have a LES simulation with periodic BC and I want to add random u,v,w fluctuations (having rms values equal to friction velocity) to trigger turbulence and I dont know how to do it in Fluent. I would appreciate your help. Cheers, Negin |
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July 11, 2013, 12:29 |
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#5 |
Senior Member
Jian Zhong
Join Date: Feb 2012
Location: Birmingham
Posts: 109
Rep Power: 14 |
Dear Negin,
I am sorry that I have not make it. I just use pressure gradient to drive my flow (just as the ChannelFoam tutorial) and select LES model in the turbulence directory. Also, I am not familiar with Fluent. But, you may try...... U = U+Random()*FACTOR My best regards, Jian |
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