# backward facing step flow

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 December 26, 2006, 00:05 backward facing step flow #1 student Guest   Posts: n/a im solving backward facing step flow.....how to give boundary condition at the exit. at the exit dp/dx=0 from y=0 to y=H or p=0 from y=0 to y=H im considering the flow is fully developed so at the exit du/dx=0 and dv/dx =0 at the top and bottom walls dp/dy=0 u= v=0 (no slip boundary condition) at the inlet im giving a parabolic profile before the expansion. please give me the correct boundary condition for pressure. thanks in advance.

March 31, 2009, 06:56
#2
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Josy
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Quote:
 Originally Posted by student ;47161 im solving backward facing step flow.....how to give boundary condition at the exit. at the exit dp/dx=0 from y=0 to y=H or p=0 from y=0 to y=H im considering the flow is fully developed so at the exit du/dx=0 and dv/dx =0 at the top and bottom walls dp/dy=0 u= v=0 (no slip boundary condition) at the inlet im giving a parabolic profile before the expansion. please give me the correct boundary condition for pressure. thanks in advance.
Hi,
Do you have the C or FORTRAN code for the 2-D unsteady backward facing step in FDM/FVM scheme ?

February 27, 2011, 03:44
#3
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Quote:
 Originally Posted by student ;47161 im solving backward facing step flow.....how to give boundary condition at the exit. at the exit dp/dx=0 from y=0 to y=H or p=0 from y=0 to y=H im considering the flow is fully developed so at the exit du/dx=0 and dv/dx =0 at the top and bottom walls dp/dy=0 u= v=0 (no slip boundary condition) at the inlet im giving a parabolic profile before the expansion. please give me the correct boundary condition for pressure. thanks in advance.
Hi,

I have these questions too.
I want use Driver and Seegmiller Paper.

What is the inlet turbulence? it is not mentioned on paper.
What should be set for outlet.
what is inlet k and epsilon for this paper?

Regards.

January 21, 2012, 09:17
Help me.
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Kyounghwa Kim
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Quote:
 Originally Posted by Josyula Hi, Do you have the C or FORTRAN code for the 2-D unsteady backward facing step in FDM/FVM scheme ?
Hello. I'm Kyounghwa.
I have same question.

I have the C code and FDM scheme by projection method.
I give inlet and outlet as follows.

Inlet : u_mean=1, u_max=3/2;
Outlet : u_mean=1, u_max=3/4;

The hight of domain is 2.
The inlet size is 1 and outlet size is 2.

Am I wrong?

ps : I'm reading "A numerical revisit of backward-facing step flow problem" by T.P.Chiang and Tony W.H. Sheu. in 1999.

 January 23, 2012, 10:41 Does anybody know? #5 New Member   Kyounghwa Kim Join Date: Jan 2012 Posts: 9 Rep Power: 5 Does anybody know? Please, give me an idea.

 February 17, 2012, 11:54 #6 Member   Join Date: Jul 2011 Posts: 59 Rep Power: 6 You should look into the open/traction boundary condtion for this sort of flow through situation. A Recent paper "Improvements on open and traction boundary condtions for the NS time splitting methods" by A.Poux JCP 2011 But I guess a simpler answer is that if the flow is steady and parabolic at the outlet then P = 0 at the outlet is ok but the you might be constraining the flow by setting du/dx = 0. Try extending the domain a little and seeing if the flow changes. Specifically the condition du/dx is not appropriate if you are near the recirculation zone or have any vortex shedding and you can't really be sure that you aren't artificially shortening the recirculation zone by imposing that condition without doing domain independence studies. BTW I have done this sort of study recently for the axisymmetric case (flow through an expansion) and I using the du/dx = 0 and p = 0 at the exit condition with a long domain if you want to compare results or have further questions.

June 9, 2013, 11:17
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Quote:
 Originally Posted by Josyula Hi, Do you have the C or FORTRAN code for the 2-D unsteady backward facing step in FDM/FVM scheme ?
hi
if you have the backward step code,in fortran or matlab, would you send me by this email
aassvvmm@yahoo.com

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