theoretically turbulent but chosen as Laminar Flow

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 August 18, 2017, 02:46 theoretically turbulent but chosen as Laminar Flow #1 Senior Member   Onur Özcan Join Date: Feb 2016 Location: Istanbul/Turkey Posts: 461 Rep Power: 12 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

 August 18, 2017, 03:34 #2 Senior Member   Cees Haringa Join Date: May 2013 Location: Delft Posts: 607 Rep Power: 0 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.

August 18, 2017, 08:14
#3
Senior Member

Onur Özcan
Join Date: Feb 2016
Location: Istanbul/Turkey
Posts: 461
Rep Power: 12
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.
Attached Images
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