Velocity Boundary Conditions for Flat Plate Domain

heisenmech · January 26, 2019, 08:42

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

LuckyTran · January 26, 2019, 15:27

It's actually is obviously velocity inlet.

heisenmech · January 28, 2019, 10:47

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,

LuckyTran · January 28, 2019, 10:54

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.

heisenmech · January 29, 2019, 06:09

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?

LuckyTran · January 29, 2019, 10:09

Yes, probably. It has been a few days since I opened Fluent. =)

heisenmech · February 1, 2019, 07:21

Fair enough

Thanks for your replies LuckTran! Cheers!

January 26, 2019, 08:42	Velocity Boundary Conditions for a wall	#1
heisenmech Member Oguzhan Join Date: Aug 2017 Posts: 38 Rep Power: 9	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 10:43.

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January 26, 2019, 15:27		#2
LuckyTran Senior Member Lucky Join Date: Apr 2011 Location: Orlando, FL USA Posts: 5,761 Rep Power: 66	It's actually is obviously velocity inlet.

January 28, 2019, 10:47		#3
heisenmech Member Oguzhan Join Date: Aug 2017 Posts: 38 Rep Power: 9	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, 10:54		#4
LuckyTran Senior Member Lucky Join Date: Apr 2011 Location: Orlando, FL USA Posts: 5,761 Rep Power: 66	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, 10:09		#6
LuckyTran Senior Member Lucky Join Date: Apr 2011 Location: Orlando, FL USA Posts: 5,761 Rep Power: 66	Yes, probably. It has been a few days since I opened Fluent. =)

February 1, 2019, 07:21		#7
heisenmech Member Oguzhan Join Date: Aug 2017 Posts: 38 Rep Power: 9	Fair enough Thanks for your replies LuckTran! Cheers!