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Old   June 15, 2010, 14:33
Default Expression as boundary condition
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kits youhara
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Hello Everybody! I would like to pose a question.

I am trying to implement different boundary along the same wall. e.g. velocity of 0[m/s] for the first 10mm and 5[m/s] for the next 10mm. First of all, is this done by an expression?
If yes, how exactly? is there the possibility to insert a branch equation in the expressions? Couldn't really find something in the help section......
Any ideas welcome. Ty!
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Old   June 15, 2010, 15:07
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Slice your wall surfaces, then mesh it again, and you will get in CFX-pre this surfaces separately (in mesh regions as primitive's or "named" faces). Now you can set them different velocities. Or if you want to create a continous velocity function along a direction?
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Old   June 15, 2010, 18:26
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You can split the wall as Attila suggests, but you can also use a CEL expression to do it. You can use the step() function or if/then statements to generate the function, or you can use a 1D interpolation function with distance along the wall as the input variable. All these options are very simple to do.
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Old   June 16, 2010, 08:45
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Just to complement the previous answers you can also divide the wall using the Operation Imprint Faces in the extrude feature from the 3D features toolbar. I think itīs always a good practice to use the least number of "blocks" as possible...

Regards and good luck
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Old   June 16, 2010, 09:04
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Hello and thank you for your answers! I already tried a user function and it seems to work! Maybe I'll also try antonio's suggestion but I never done something like that again! Thanks anyway!
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