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How to determine the boundary conditions in LES simulation |
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October 22, 2018, 10:42 |
How to determine the boundary conditions in LES simulation
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#1 |
New Member
Yuan Jiahui
Join Date: Oct 2018
Posts: 9
Rep Power: 7 |
Hi everyone,
I am trying to simulate a case using LES model (dynamicKEqn model). The case is similar to pitzDaily and I only know the initial inlet velocity field (0.455 0 0). I checked online for the boundary conditions that I should use and I found that I should use fixedvalue for inlet and inletoutlet for the outlet, but I have doubt about the initial values of k and other boundary conditions. And I also want to get better understand of dynamicKEqn model. Any information about it helps. Regards |
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October 22, 2018, 12:30 |
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#2 |
Senior Member
Michael Alletto
Join Date: Jun 2018
Location: Bremen
Posts: 616
Rep Power: 16 |
A constant velocity at the inlet is not a good idea for LES. Since an inlet is an artificial boundary condition the boundary condition should resample as close as possible what happens in reality there.
For turbulent flows you'll never have a constant profile. Usually one has to either synthetic turbulence at the inflow or use a precursor simulation with periodic boundary conditions as inflow. |
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October 22, 2018, 13:05 |
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#3 |
Senior Member
Join Date: Aug 2015
Posts: 494
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To add to this, here's a paper that compares choices for the inlet velocity bc (assuming incompressibility) : https://www.sciencedirect.com/scienc...95717711006820.
The reference for the dynamicKEqn model is also provided in the corresponding .H file. It is : Kim, W and Menon, S. (1995). A new dynamic one-equation subgrid-scale model for large eddy simulation. In 33rd Aerospace Sciences Meeting and Exhibit, Reno, NV, 1995. Caelan |
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October 23, 2018, 08:20 |
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#4 | |
New Member
Yuan Jiahui
Join Date: Oct 2018
Posts: 9
Rep Power: 7 |
Quote:
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October 23, 2018, 10:57 |
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#5 |
Senior Member
Michael Alletto
Join Date: Jun 2018
Location: Bremen
Posts: 616
Rep Power: 16 |
by aware that k in for LES means the subgrid scale turbulent kinetic energy. I.e. the part of the spectrum which is not resolved. So it depends strongly on the grid resolution and of the problem.
What are you trying to simulate? |
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October 23, 2018, 11:10 |
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#6 | |
Senior Member
Join Date: Aug 2015
Posts: 494
Rep Power: 15 |
Quote:
Caelan |
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Tags |
boundary conditions, dynamickeqn, les |
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