No Slip Boundary Condition

ashtonJ · March 12, 2011, 20:30

Dear All

I simulated a fluid flow in a pipe. When I considered the velocity vectors in CFD Post I found out that on the pipe wall axial velocity is not zero while I used no-slip boundary condition on the wall. Does anybody know why?

Regards,
AshtonJ

ghorrocks · March 13, 2011, 06:52

Look in the documentation for an explanation of hybrid and conservative variables. That is why the velocity at the wall appears to not be zero.

But rest assured that CFX is correctly applying the no slip boundary with zero velocity walls.

ashtonJ · May 16, 2011, 22:47

Hi

I want to plot axial velociy versus radius at the throat of a constricted pipe. I changed the axial velocity from conservative to hybrid variable however when I plot axial velocity, its boundary values are not zero. Do you know how I can plot the axial velocity with zero values on the boundaries.

Regards,
ashtonJ

Quote:

Originally Posted by ghorrocks

Look in the documentation for an explanation of hybrid and conservative variables. That is why the velocity at the wall appears to not be zero.

But rest assured that CFX is correctly applying the no slip boundary with zero velocity walls.

ghorrocks · May 17, 2011, 20:05

Is the point at the boundary exactly on the boundary?

The hybrid values should have zero at the wall. If not then you have done something wrong.

ashtonJ · May 17, 2011, 20:07

Thank you very much. You are right my point was not exectly on the wall.

Regards,
ashtonJ

Quote:

Originally Posted by ghorrocks

Is the point at the boundary exactly on the boundary?

The hybrid values should have zero at the wall. If not then you have done something wrong.

March 12, 2011, 20:30	No Slip Boundary Condition	#1
ashtonJ Senior Member Ashkan Javadzadegan Join Date: Sep 2010 Posts: 255 Rep Power: 17	Dear All I simulated a fluid flow in a pipe. When I considered the velocity vectors in CFD Post I found out that on the pipe wall axial velocity is not zero while I used no-slip boundary condition on the wall. Does anybody know why? Regards, AshtonJ

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March 13, 2011, 06:52		#2
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,871 Rep Power: 144	Look in the documentation for an explanation of hybrid and conservative variables. That is why the velocity at the wall appears to not be zero. But rest assured that CFX is correctly applying the no slip boundary with zero velocity walls.

May 17, 2011, 20:05		#4
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,871 Rep Power: 144	Is the point at the boundary exactly on the boundary? The hybrid values should have zero at the wall. If not then you have done something wrong.