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Boundary conditions for K and Omega in SST model |
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November 26, 2017, 13:39 |
Boundary conditions for K and Omega in SST model
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#1 |
Member
Join Date: May 2017
Posts: 41
Rep Power: 9 |
Hello everyone,
I am using SST turbulence model for my simulations and I would like to know what type of boundary conditions for "K" and "Omega" are applied at different markers. In the config file the boundary conditions for pressure and velocity can be explicitly defined but I could not find any information about the type of boundary conditions used for "K" and "Omega" at the inlet, outlet or at the walls. Can someone please give me some information about the default settings of these BCs? Thanks in advance. |
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November 27, 2017, 05:17 |
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#2 |
Super Moderator
Tim Albring
Join Date: Sep 2015
Posts: 195
Rep Power: 11 |
Hi Ryan,
at the inlet k and Omega are computed using the values set with FREESTREAM_TURBULENCEINTENSITY (default 0.05) and FREESTREAM_TURB2LAMVISCRATIO (default 10) in the config file. At the wall k is set to zero and omega is defined as described here: https://turbmodels.larc.nasa.gov/sst.html At the outlet the values are extrapolated from the interior. I hope that helps. Tim
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November 27, 2017, 18:29 |
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#3 | |
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Posts: 41
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July 19, 2021, 21:30 |
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#4 |
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Thanks for the explanations. I have a few questions regarding the k omega SST turbulence model initialization in a cylindrical nozzle flow with recirculating flow at the outlet caused due to kelvin helmholtz instability at the nozzle exit. I am doing 2D axisymmetric simulations with a wedge BC.
1. How do I set the k, omega BC at outlet to take care of the recirculating flow? I could use inletOutlet with inletValue of 0 for k but that's unphysical. 2. What value of y+ should I ensure near the walls. I am using a wall function for k and omega. My Re=25000, which is a high Re case and I heard that k omega is for Low Re. 3. If I go to a fine mesh with y+ <1, should I switch off the wall function? |
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July 23, 2021, 03:55 |
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#5 | |||
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bigfoot
Join Date: Dec 2011
Location: Netherlands
Posts: 633
Rep Power: 18 |
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yes, but this is done automatically when y+<5. That reminds me that I will add a config option to control this parameter. |
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boundaries condition, k-omega, rans modelling, sst k-omega, su2 |
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