# how can i calculate k & epsilon values in OpenFOAM?

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December 25, 2014, 05:42
how can i calculate k & epsilon values in OpenFOAM?
#1
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Duong Tung
Join Date: Nov 2014
Location: Ho Chi Minh city, Viet Nam
Posts: 24
Rep Power: 4
Hello all,

I have some problems when i try to run pisoFoam (i want to use RANS to solve it) to solve elbow problem. You can see in the attached file the geometry and meshing

I can not calculate the values of k and epsilon to input into OpenFOAM (file k & epsilon in the 0 directory).
Can you help me to solve this problem and run it.
Attached Images
 12-25-2014 4-30-06 PM.jpg (42.3 KB, 17 views)

December 25, 2014, 06:59
#2
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Derek Mitchell
Join Date: Mar 2014
Posts: 134
Rep Power: 5
Quote:
 Originally Posted by gnut1989 Hello all, I have some problems when i try to run pisoFoam (i want to use RANS to solve it) to solve elbow problem. You can see in the attached file the geometry and meshing I can not calculate the values of k and epsilon to input into OpenFOAM (file k & epsilon in the 0 directory). Can you help me to solve this problem and run it.
Have you looked at page 40 in the OpenFOAM userguide.
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December 25, 2014, 07:11
#3
New Member

Duong Tung
Join Date: Nov 2014
Location: Ho Chi Minh city, Viet Nam
Posts: 24
Rep Power: 4
Quote:
 Originally Posted by derekm Have you looked at page 40 in the OpenFOAM userguide.
Thanks Derekm very much!
I've seen it and tried to calculate.
The result for k = 1/2 (U'x^2 + U'y^2 + U'z^2) = 1/2 (0.04 + 1) = 0.52 m2 s-2
is it right or wrong?
You can help me calculate the value of epsilon????

Thanks again and hope that you merry christmas!!!!!

Duong Tung

 December 25, 2014, 11:33 #4 Senior Member     Hasan K.J. Join Date: Dec 2011 Location: Bristol, United Kingdom Posts: 196 Rep Power: 6 Hey Duong Tung, It is straight forward have a look at this and calculate your K, E, W etc. http://www.cfd-online.com/Wiki/Turbu...ary_conditions Happy simulation all the best, Hasan K.J Last edited by Alhasan; December 25, 2014 at 13:04.

December 25, 2014, 22:55
#5
New Member

Duong Tung
Join Date: Nov 2014
Location: Ho Chi Minh city, Viet Nam
Posts: 24
Rep Power: 4
Quote:
 Originally Posted by Alhasan Hey Duong Tung, It is straight forward have a look at this and calculate your K, E, W etc. http://www.cfd-online.com/Wiki/Turbu...ary_conditions Happy simulation all the best, Hasan K.J
Hello Hasan,

Thanks a lot for your suggestion! I have looked at the link and calculated in the attached excel file. Could you please check it for me?

I am still confused that I have two inlets (1 & 2) so i have to calculate two values for epsilon. Is it right or wrong???? And after inputting the value of k and epsilon into k & epsilon files at 0 directory in OpenFoam, I can run this problem????

Attached Files
 calculation.xlsx (9.6 KB, 7 views)

 December 25, 2014, 23:01 #6 Senior Member     Hasan K.J. Join Date: Dec 2011 Location: Bristol, United Kingdom Posts: 196 Rep Power: 6 Hey Duong Tung, It looks like reasonable values to me, take it as a guidance value and run your simulations when you compare it with the experimental data you will get a better idea of where you stand !! All the best, Hasan K.J gnut1989 likes this.

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