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Dependency of turbulence model on mesh size

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Old   September 20, 2007, 00:14
Default Dependency of turbulence model on mesh size
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Kushagra Mittal
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Hi,

The flow I am trying to simulate is highly swirl in nature. I started with a very coarse mesh without resolving the near wall mesh. I used 4 mm tetra element with T-Grid scheme while the diameter of circular section is 76 mm.

What I find, velocity profiles and other results are exactly same for laminar and turbulent models; respectively. The reynolds number would be around 3*10^5 to 5*10^5.

I can be assumed a beginner in CFD world. Could you please through some light on importance of mesh size and near wall resolution on turbulence models. I have studied about y+ and wall function but I am wondering if turbulent models might not affect simulations AT ALL even with a coarse mesh and high y+. Should not I see some difference in my solutions.

Thanks in advance, KM.
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Old   September 20, 2007, 18:51
Default Re: Dependency of turbulence model on mesh size
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Glenn Horrocks
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Hi,

Wall functions will not be the problem with your simulation.

If your flow has high swirl then forget about all the two equation turbulence models. This means k-epsilon, k-omega are no good as none of them can handle swirling flows. The only exception is the SST model has a curvature correction option as a beta feature. This may mean the SST model is OK, but I have never used this option so no guarantees.

For swirling flows you really need to use a Reynolds Stress based model or DES/LES. Of course you need to use wall functions with these models but at least they can handle the basic physics of the flow.

Glenn Horrocks
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