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Boundary Conditions of Turbulent Channel Flow (DNS) |
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May 24, 2023, 05:11 |
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#21 | |
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Quote:
Periodicity gives the correct bc for velocity and the periodic pressure part. If you don't want to use periodicity you need to amke the flow develop naturally in a sufficiently long tube. In that case you just use a given velocity inlet and a pressure outlet. |
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May 24, 2023, 07:25 |
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#22 |
Senior Member
Lucky
Join Date: Apr 2011
Location: Orlando, FL USA
Posts: 5,737
Rep Power: 66 |
Please clarify your entire boundary conditions for both pressure and velocity. It works means you get a solution that looks like what? It looks like fully developed and looks exactly like the DNS results or does it look like an entirely different flow but is non-zero velocity and so you are happy with any result? In the second case you get a zero velocity so you are instantly unhappy, that is understood.
You use pressure at inlet and outlet without a forcing term. What about the velocity? It should be periodic for velocity. You apply a forcing term. What is your BC for pressure? And what is the BC for velocity? It should be periodic for pressure and periodic for velocity. I have simulated with pressure jump condition and forcing term in 2D and 3D for both cases and I can confirm it works. I know that the others responding to this thread have done similar cases as well. And there is also quite a breadth of literature including the paper you cited that shows it has been done before. It's not a hoax. We're really just trying to help you figure out why it doesn't work for you but does work for everybody else. Make sure you are using periodic conditions! |
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May 24, 2023, 07:31 |
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#23 |
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Filippo Maria Denaro
Join Date: Jul 2010
Posts: 6,833
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And there is a physical difference between inlet/outlet conditions and periodicity. The former simulates a spatial evolving BL, the latter the temporal evolving BL.
I suppose a steady Poiseuille flow is obtained by fixing just the pressure at inflow and outflow, maybe this is the problem that “works”. |
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