Unwanted wall

prince_pahariaa · December 23, 2011, 06:11

Hii friends

I am suspecting an unwanted wall inside geometry (sudden obstruction in flow) because of which i am getting reverse flow as warning. I have checked manually for any double faces in my geometry in GAMBIT but fail to obtain any thing.

What can be the other reason for the presence of that unwanted wall. Any insight will be helpful ??

prince_pahariaa · December 23, 2011, 06:15

The flow is reduced in left branch (It should be identical to right branch)

Far · December 24, 2011, 01:17

any difference in boundary conditions, meshing and geometry on both sides? if every thing is same then we can look into the issue further by inspecting the dbs/case file

prince_pahariaa · December 25, 2011, 23:59

Thanks Far for showing interest..

No there is no change in boundary condition or mesh. All are same. My geometry is annular cylinder. It will be very helpful if u can see my dbs or case file How can i send u ??

Regards

BMCombustor · December 26, 2011, 14:29

Quote:

Originally Posted by prince_pahariaa

Thanks Far for showing interest..

No there is no change in boundary condition or mesh. All are same. My geometry is annular cylinder. It will be very helpful if u can see my dbs or case file How can i send u ??

Regards

If it is annular, why don't you use a 2-D axisymmetric model instead of a 3-D? That way, you could better understand which side reflects realistic result!

duri · December 27, 2011, 10:27

Can you give static and total pressure plots.

prince_pahariaa · December 28, 2011, 00:35

Hi duri

Please check static and total pressure plot.

Thank you.

duri · December 28, 2011, 04:19

Flow is not symmetric near the nose. Total pressure in the diffuser is high due to higher velocity in left side. There is no difference in static pressure between left and right. In case of wall static pressure should go up. In this case total pressure is droping down, loss in total pressure indicates separation or incorrect boundary layer (probably).

I think there is no wall. Is this solution fully converged?. Is wall BC and Wall treatment, Y+ are same on both sides?. I think you have used pressure outlet BC and forced static pressure, if so, try changing it to outflow (this can clearly show rise in static pressure at walls near the outlet).
If you still doubt about presence of wall. Use symmetry boundary condition and solve only left side, you could get some clue.

prince_pahariaa · December 29, 2011, 01:01

Thankss duri..

I will try and implement the suggestion.. It helps a lot..

December 23, 2011, 06:11	Unwanted wall	#1
prince_pahariaa Member prince Join Date: Jun 2011 Posts: 56 Rep Power: 14	Hii friends I am suspecting an unwanted wall inside geometry (sudden obstruction in flow) because of which i am getting reverse flow as warning. I have checked manually for any double faces in my geometry in GAMBIT but fail to obtain any thing. What can be the other reason for the presence of that unwanted wall. Any insight will be helpful ??

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December 24, 2011, 01:17		#3
Far Super Moderator Sijal Join Date: Mar 2009 Location: Islamabad Posts: 4,553 Blog Entries: 6 Rep Power: 54	any difference in boundary conditions, meshing and geometry on both sides? if every thing is same then we can look into the issue further by inspecting the dbs/case file

December 25, 2011, 23:59		#4
prince_pahariaa Member prince Join Date: Jun 2011 Posts: 56 Rep Power: 14	Thanks Far for showing interest.. No there is no change in boundary condition or mesh. All are same. My geometry is annular cylinder. It will be very helpful if u can see my dbs or case file How can i send u ?? Regards

December 27, 2011, 10:27		#6
duri Senior Member duri Join Date: May 2010 Posts: 245 Rep Power: 16	Can you give static and total pressure plots.

December 28, 2011, 04:19		#8
duri Senior Member duri Join Date: May 2010 Posts: 245 Rep Power: 16	Flow is not symmetric near the nose. Total pressure in the diffuser is high due to higher velocity in left side. There is no difference in static pressure between left and right. In case of wall static pressure should go up. In this case total pressure is droping down, loss in total pressure indicates separation or incorrect boundary layer (probably). I think there is no wall. Is this solution fully converged?. Is wall BC and Wall treatment, Y+ are same on both sides?. I think you have used pressure outlet BC and forced static pressure, if so, try changing it to outflow (this can clearly show rise in static pressure at walls near the outlet). If you still doubt about presence of wall. Use symmetry boundary condition and solve only left side, you could get some clue.

December 29, 2011, 01:01		#9
prince_pahariaa Member prince Join Date: Jun 2011 Posts: 56 Rep Power: 14	Thankss duri.. I will try and implement the suggestion.. It helps a lot..