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March 20, 2018, 03:46 |
Steady Laminar Backwards Facing Step
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#1 |
Member
E
Join Date: Mar 2018
Posts: 77
Rep Power: 8 |
Hello!
I am writing code to solve 2D Steady Laminar Backwards Facing Step problem for Reynolds number up to 400 through finite differences with dimensionless 2D Navier-Stokes equations. The boundary conditions are the following: Inlet: Parabolic profile for u, v=0, pressure calculated by the pseudo-compressibility continuity equation. Walls: u=v=0, pressure calculated by the pseudo-compressibility continuity equation. Outlet: θu/θx=0, θv/θx=0, p=0. I am running the code but after the step the flow has an upwards direction where it would be expected going downwards with recirculation area. Any help? Thank you very much. |
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March 20, 2018, 03:59 |
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#2 | |
Senior Member
Filippo Maria Denaro
Join Date: Jul 2010
Posts: 6,782
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Quote:
I suggest to debug the code to find some bugs... have a look to the pressure equation that must have suitable Neumann BC.s |
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March 20, 2018, 04:03 |
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#3 |
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Thank you FMDenaro.
Are the boundary conditions that I am using correct except for the pressure boundary conditions? |
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March 20, 2018, 04:06 |
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#4 | |
Senior Member
Filippo Maria Denaro
Join Date: Jul 2010
Posts: 6,782
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Quote:
I suggest not to use the constant pressure at the exit but the condition derived from the fact that you supposed du/dx=0 in the continuity equation evaluated at the exit. You will also easily see that you get v=0 along the outflow. |
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March 20, 2018, 04:17 |
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#5 |
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Thank you. I will check it.
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March 20, 2018, 04:47 |
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#6 |
Senior Member
Filippo Maria Denaro
Join Date: Jul 2010
Posts: 6,782
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Are you using a second order central discretization on staggered grid?
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March 20, 2018, 04:53 |
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#7 |
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I am working with finite differences and in some cases with second order central discretization and in another cases with forward or backward discretization.
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March 20, 2018, 05:21 |
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#8 |
Senior Member
Filippo Maria Denaro
Join Date: Jul 2010
Posts: 6,782
Rep Power: 71 |
what about the colocation of the variables on the grid?
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March 20, 2018, 06:40 |
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#9 |
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March 21, 2018, 00:12 |
Bfs
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#10 |
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Selig
Join Date: Jul 2016
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March 22, 2018, 15:09 |
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#11 | |
Member
E
Join Date: Mar 2018
Posts: 77
Rep Power: 8 |
Quote:
I wrote SIMPLE algorithm for the same problem but the velocity field is not the expected. Is there any advice about the correct boundary conditions of the problem? Thank you. |
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