Two Questions for Turbulence Modeling

mohammad.sarfaraz · June 16, 2012, 03:09

Hi all
I have 2 questions, which I would be thankful for recieving their answers:

1- When using k-epsilon model, what is the B.C. for the values of k and epsilon?
2- When adopting log. wall law, how does it work? give an example.

Regards,

mb.pejvak · June 17, 2012, 00:43

I recommend you to read "An Introduction to Computational Fluid Dynamics" by Versteeg. it is good for start. and " Turbulence modeling for CFD" by Wilcox D.C. is very good in explanation of wall function.

chris85 · June 18, 2012, 06:35

Also good book "Computational Methods for Fluid Dynamics" by Ferziger is good.

the k-epsilon model cant model the near wall region and thus a wall function is needed to solve the sub viscour near wall region. For this your meshing needs to be adequate so that y+ is between 30 and 300. This is what it is describing when mentioned log law.

Also your BC for the flow and values for k and epsilon will be dependant on the flow. See software help for equations which may be used to get these values.

June 16, 2012, 03:09	Two Questions for Turbulence Modeling	#1
mohammad.sarfaraz Member Mohammad Sarfaraz Join Date: Feb 2010 Posts: 35 Rep Power: 16	Hi all I have 2 questions, which I would be thankful for recieving their answers: 1- When using k-epsilon model, what is the B.C. for the values of k and epsilon? 2- When adopting log. wall law, how does it work? give an example. Regards,

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June 17, 2012, 00:43		#2
mb.pejvak Senior Member Mehdi Baba Mehdi Join Date: Jan 2011 Posts: 158 Rep Power: 15	I recommend you to read "An Introduction to Computational Fluid Dynamics" by Versteeg. it is good for start. and " Turbulence modeling for CFD" by Wilcox D.C. is very good in explanation of wall function.

June 18, 2012, 06:35		#3
chris85 New Member Chris Join Date: Nov 2011 Posts: 16 Rep Power: 14	Also good book "Computational Methods for Fluid Dynamics" by Ferziger is good. the k-epsilon model cant model the near wall region and thus a wall function is needed to solve the sub viscour near wall region. For this your meshing needs to be adequate so that y+ is between 30 and 300. This is what it is describing when mentioned log law. Also your BC for the flow and values for k and epsilon will be dependant on the flow. See software help for equations which may be used to get these values.