initial condition for k and epsilon for frozen rotor case.

student666 · June 6, 2014, 12:19

Hi all,

I'm trying to simulate a fan inside channel, using MRF source terms and simpleFoam.

I'm looking for help how to calculate values of k and epsilon for a wall bounded flow of such type of case.

I look into literature, but I was able to find correlation only for free-stream flows, or bounded flows with constant section.

One thing I have doubt is: in my case, I have many sections for each channel, and I don't have a free stream velocity as it changes according to section's change.

How can I set proper initial condition for k and epsilon?

I'm a bit confused and I would like to have a little help to clarify myself.

Thanks a lot.

Meister · June 12, 2014, 05:38

Hi,

Im not sure if my answer is what you are looking for. I think i would first calculate the values with the "ordinary" formula for k and epsilon:
k=1.5*(U*I_U)^2
epsilon=(0.09^(0.75)*k^(1.5))/(L_t)
L_t=L_U*L
You can try to change I_U (turbulence intensity). Im sure there is a description in the wiki here as well.

Regards

Thomas

June 6, 2014, 12:19	initial condition for k and epsilon for frozen rotor case.	#1
student666 Senior Member M. C. Join Date: May 2013 Location: Italy Posts: 286 Blog Entries: 6 Rep Power: 16	Hi all, I'm trying to simulate a fan inside channel, using MRF source terms and simpleFoam. I'm looking for help how to calculate values of k and epsilon for a wall bounded flow of such type of case. I look into literature, but I was able to find correlation only for free-stream flows, or bounded flows with constant section. One thing I have doubt is: in my case, I have many sections for each channel, and I don't have a free stream velocity as it changes according to section's change. How can I set proper initial condition for k and epsilon? I'm a bit confused and I would like to have a little help to clarify myself. Thanks a lot.

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June 12, 2014, 05:38		#2
Meister New Member Thomas Join Date: May 2014 Posts: 14 Rep Power: 11	Hi, Im not sure if my answer is what you are looking for. I think i would first calculate the values with the "ordinary" formula for k and epsilon: k=1.5(UI_U)^2 epsilon=(0.09^(0.75)k^(1.5))/(L_t) L_t=L_UL You can try to change I_U (turbulence intensity). Im sure there is a description in the wiki here as well. Regards Thomas