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theoretically turbulent but chosen as Laminar Flow

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Old   August 18, 2017, 02:46
Default theoretically turbulent but chosen as Laminar Flow
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Onur Özcan
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Hi all,

I have been working on VOF model for long time. I got still quite problems to solve accurately,anyway,changed to flow model as laminar but actually flow is theoretically turbulent.Then, continuity residuals changed quite posivitely but it is not still enough to get accurately better.

How does FLUENT respond in affirmative by changing laminar flow but not turbulent ?

Kind Regards,

Onur Özcan
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Old   August 18, 2017, 03:34
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Cees Haringa
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Well, laminar flow just means you are solving the NS equations without any modeling assumptions for turbulence. If the lengthscales of turbulence are larger than your grid size, it's not an issue - you are just conducting direct numerical simulation.

What is the type of problem that you are solving? If it is something like a single bubble, it might be that your grid size and the kolmogorov scale are reasonably similar. If it's a dam break problem or so, no way.

More generally, before setting up the simulation, it is good to calculate what the ratio between lengtscales in your problem is, and to set your simulation strategy (laminar/turbulent) accordingly.
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Old   August 18, 2017, 08:14
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Onur Özcan
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Project: Glass distribution in glass packaging products.

As for CFD,we only conducts processes of final blowing in order to get precise simulation results for glass distribution.

Hint:Inlet diameter for air that enters to system is 18.36 mm (Reynolds number :7541.41 t=0 s) and it is not passing through in constant cross section as well as basic pipe flow. So, I do not know how to calculate the lenght scales of flow whether it is turbulent or laminar not.

Model is as attached.There are 3 domains.Two of them are air domains in the first time. One of which is affected by pressured air that gets in. There will be two domains as glass adheres on surface of glass packaging product.
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