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LES turbulence decaying in channel

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Old   July 3, 2008, 17:11
Default LES turbulence decaying in channel
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cfdIsMad
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Hi

I am running a channel flow using LES. My problem is that turbulence after developing for a bit starts to decay in channel. And after a while I see zero turbulence in my domain. What can I do under such circumstances to sustain the turbulence. Thank you for your answer.

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Old   July 4, 2008, 07:44
Default Re: LES turbulence decaying in channel
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matej
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Hi!

there are few things you can do here. But it all depends on your settings of the case.

try to be more specific on your boundary conditions and parameteres of the flow. with those information someone will surely help you. Few questions you should answer here:

1\ what is your inlet conditions? (in a channel flow, typially the outlet parameters are used as inlet, or some forcing must be used to keep the turbulence going)

2\ what is your mesh like? strucutred hexa? 2a\ is your mesh fine enough at the wall? 3\ what do you do at the wall? 4\ is your channel long enough? 5\ what is your Courant number? 6\ what discretisation are you using (space and time)?

answering those questions should make it clear where the problem is.

matej
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Old   July 4, 2008, 08:40
Default Re: LES turbulence decaying in channel
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cfdIsMad
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Hi Matej

Thank you for your answer. I am using periodic boundary with pressure drop between inlet and outlet. I am using RANS solution as an initial guess. Mesh is hexa unstructured with very low YPlus values, below 1. Courant number is 0.6 and the length of channel is 1.6m. Discretisation scheme is central difference.

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