# Set the inflow condition from the outflow

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 January 26, 2010, 03:06 Set the inflow condition from the outflow #1 New Member   Yue Zhang Join Date: Dec 2009 Posts: 4 Rep Power: 9 Hi, I want to get the outflow velocity value and set them as the inlet velocity. For example, the distance between the inlet and outlet is 10 meters. I will set U_inlet(x,y,z,t) = U_outlet(x+10,y,z,t). How to make it? I have read the User Fortran. But I do not know how to get a obtain a velocity from point(x,y,z). Can you help me? Thank you!

 January 26, 2010, 17:21 #2 Super Moderator   Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 13,991 Rep Power: 107 No, this is not the way to do it. You will need to use a periodic boundary condition. V12 has a lot of extra features for this type of boundary to do exactly what you are trying to do.

 January 26, 2010, 21:36 #3 New Member   Yue Zhang Join Date: Dec 2009 Posts: 4 Rep Power: 9 Hi ghorrocks, thank you. I find that in V12 they are rotational periodic condition such as turbo. But actually I want to rescale the outflow velocity and reintroduce it to the inlet. I am afraid that 's not regular periodic interface operation. So is there any way to realize it?

 January 26, 2010, 21:47 #4 Super Moderator   Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 13,991 Rep Power: 107 Can you explain what you are trying to do? What you are describing does not sounds physically possible as it does not conserve mass.

 January 26, 2010, 22:22 #5 New Member   Yue Zhang Join Date: Dec 2009 Posts: 4 Rep Power: 9 I want to do a transient simulation. The inflow velocity at the inlet is computed from the outflow velocity at the outlet on every time step. For example, U_inlet(x,y,z,t)=2*U_outlet(x,y,z,t). This is just an example. Actually the transformation is a little complex and not just multiply 2. Is this clear?

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