# Velocity Boundary Conditions for Flat Plate Domain

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 January 26, 2019, 07:42 Velocity Boundary Conditions for a wall #1 Member   Oguzhan Join Date: Aug 2017 Posts: 38 Rep Power: 8 Hi all, I'm trying to simulate a flow over flat plate for some validation purposes. What I would normally do is to create a rectangular box and treat the top surface as symmetry. However, the paper I'm looking at defines the top boundary condition as follows; "The top boundary conditions are u=Uinf, v=VBlasius, w=0, and T=Tinf " Does anyone know how to define (in Fluent) such conditions on top of a domain (which is not an inlet obviously), which is basically a plate? Cheers, heisenmech Last edited by heisenmech; January 26, 2019 at 09:43.

 January 26, 2019, 14:27 #2 Senior Member   Lucky Join Date: Apr 2011 Location: Orlando, FL USA Posts: 5,671 Rep Power: 65 It's actually is obviously velocity inlet.

 January 28, 2019, 09:47 #3 Member   Oguzhan Join Date: Aug 2017 Posts: 38 Rep Power: 8 Thanks for the reply. I wasn't sure about that until I gave it a try with quick setup simulation. I'm still wondering though why I cant use (or why one would use velocity inlet) a simple symmetry BC on top since the results are pretty much the same. Any thoughts? Cheers,

 January 28, 2019, 09:54 #4 Senior Member   Lucky Join Date: Apr 2011 Location: Orlando, FL USA Posts: 5,671 Rep Power: 65 In my experience, more people use a symmetry BC at the top (or slip walls) than anything else. Yeah I can't tell you why this one particular person think it's unusable. To each their own. The choice of which to use is by the user. But each has to verify that they have a proper boundary layer in their simulation after-the-fact. The BC that you want is the natural boundary condition these are all just ways to mimic that behavior. There is also a freestream BC in Fluent which might even be better than symmetry/slip/velocity BC.

January 29, 2019, 05:09
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Oguzhan
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Quote:
 Originally Posted by LuckyTran In my experience, more people use a symmetry BC at the top (or slip walls) than anything else. Yeah I can't tell you why this one particular person think it's unusable. To each their own. The choice of which to use is by the user. But each has to verify that they have a proper boundary layer in their simulation after-the-fact. The BC that you want is the natural boundary condition these are all just ways to mimic that behavior. There is also a freestream BC in Fluent which might even be better than symmetry/slip/velocity BC.
Do you mean "pressure far field" BC by free stream BC?

 January 29, 2019, 09:09 #6 Senior Member   Lucky Join Date: Apr 2011 Location: Orlando, FL USA Posts: 5,671 Rep Power: 65 Yes, probably. It has been a few days since I opened Fluent. =)

 February 1, 2019, 06:21 #7 Member   Oguzhan Join Date: Aug 2017 Posts: 38 Rep Power: 8 Fair enough Thanks for your replies LuckTran! Cheers!

 Tags boundary condition u, boundary conditions, flat plate