# channel flow question

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 April 28, 2008, 16:11 channel flow question #1 keith Guest   Posts: n/a Hi everyone, I am currently trying to verify my finite volume code with the a channel flow problem(Re_tau=180). My question is regarding the setup of the problem. I prescribed a constant pressure gradient to drive the flow. Do I also prescribe the wall shear stress value(Tau_w) or should I just set the wall boundary condition as no slip? Please help me as I am still a little confused.

 April 29, 2008, 09:21 Re: channel flow question #2 otd Guest   Posts: n/a no-slip

 April 29, 2008, 10:25 Re: channel flow question #3 keith Guest   Posts: n/a otd, thanks for the quick reply. If the wall boundary was set to no-slip(no wall shear prescribed), how does the program know the "roughness" of the channel?

 April 29, 2008, 20:26 Re: channel flow question #4 otd Guest   Posts: n/a I don't know. It has to depend on what you've built into the code. So it's a modeling question - and, if it's your code, you're the modeler.

September 13, 2012, 05:42
wall SHear stress in cahnnel flow
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ronak
Join Date: Jul 2011
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Quote:
 Originally Posted by keith ;54939 Hi everyone, I am currently trying to verify my finite volume code with the a channel flow problem(Re_tau=180). My question is regarding the setup of the problem. I prescribed a constant pressure gradient to drive the flow. Do I also prescribe the wall shear stress value(Tau_w) or should I just set the wall boundary condition as no slip? Please help me as I am still a little confused.

Hi ,I m also work with some DNS data IN RE-taw=180.
I have 130*130*130* grid point in 5 timewindows.
The pressure Gradient is 1.I try to find Taw-Av on the wall. it should be near 1, but My simulation give me a wrong value.
I USED THIS statement for TAW.
IS IT POSSIBLE TO HELP ME?
taw(i,k,n)=(U(i,1,k,n)-U(i,1,0,n))/(yc(1)-yc(0))

I OBTAIN the diffrence of u at each grid for J=0 AND 1

September 14, 2012, 05:14
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Filippo Maria Denaro
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Quote:
 Originally Posted by MD276 Hi ,I m also work with some DNS data IN RE-taw=180. I have 130*130*130* grid point in 5 timewindows. The pressure Gradient is 1.I try to find Taw-Av on the wall. it should be near 1, but My simulation give me a wrong value. I USED THIS statement for TAW. IS IT POSSIBLE TO HELP ME? taw(i,k,n)=(U(i,1,k,n)-U(i,1,0,n))/(yc(1)-yc(0)) I OBTAIN the diffrence of u at each grid for J=0 AND 1
if you fix the pressure gradient then the tau wall will be not necessarily exact ... some percent of difference is acceptable.

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