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[Variation of the solution as the time step varies. RANS/Channel/Moser] |
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October 28, 2011, 03:06 |
[Variation of the solution as the time step varies. RANS/Channel/Moser]
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#1 |
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Join Date: Mar 2011
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Dear Foamers,
While testing the differents two equations eddy viscosity models with pisoFoam (modified) on a channel I experienced difficulties. With the k-w models, the converged mean profile and turbulent kinetic energy are time steps dependent. According to this, I would expect better results as I reduce the time step, or it is the reverse. As the time step is reduced the wall shear stress decreases and therefore the pressure drop I apply (to maintain a constant mass flux over my stream-wise periodic length). Result is that the Re_tau is way to low... Target Re_tau is 395 as in Moser simulations. The corresponding tau_wall and Re_tau is given in the table below (as a function of the time step): Uploaded with ImageShack.us Does anyone experienced such results with the k-w and k-w SST models? My mesh is refined in the near wall region and I am using omegaWallfunction to provide proper boundary conditions to omega. PS: I am not observing the same behavior with "resolved" (without wallFunctions) LaunderSharmaLowKE. I therefore suspect the trouble from the boundary condition of omega or the numerics... I'm using OpenFoam 1.6.x Last edited by tonkiplis; October 28, 2011 at 05:24. Reason: picture size... |
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October 29, 2011, 07:09 |
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#2 |
New Member
Join Date: Mar 2011
Posts: 12
Rep Power: 15 |
any insight? I am really confused now...
Is it a good idea to increase to bulk velocity in order to obtain the right wall shear stress? I guess not.... Last edited by tonkiplis; October 29, 2011 at 09:57. |
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