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Old   May 9, 2005, 11:16
Default LES fully developed channel flow
  #1
Gem
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I am testing Fluents 6.1 Large Eddy Simulation capability using fully developed channel flow as the test case. I have carried out the simulation, however i am having difficulties with the post-processing stage. I have enabled the data sampling for data statistics option in the iterate panel and ran the simulation for 8 flow through times. However when I display the velocity contours for the instanteous and mean x, y and z velocities they are exactly the same, the RMS values are very small. How do I enable Fluent to correctly output the instanteous, mean and RMS x, y and z velocities to display the velocity contours/data? does anyone know if there is a bug in fluent when using the data sampling option, I think it might be collecting data over one time step only and not over the 8 flow through times.
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Old   May 10, 2005, 03:23
Default Re: LES fully developed channel flow
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anindya
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I faced the same problem as yours but could not find any solution even after posting it here several times.

I have ran different cases with different settings, but everytime I saw that the mean and the instantaneous results were the same even after running them for several thousand time steps (hundred thousand or more iterations).

I strongly feel that there is a problem with LES model in Fluent 6.1.

Anindya
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Old   May 10, 2005, 05:32
Default Re: LES fully developed channel flow
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Gem
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Anindya,

Thanks for your post. Did you manage to solve the problem by using a different version of Fluent?, if so what version did you use? Did you find any alternative way of outputting the mean and instanteous velocities?

Thanks

Gem
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Old   May 10, 2005, 18:26
Default Re: LES fully developed channel flow
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Anindya
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I just had fluent 6.2 installed. I am going to run it and see if the new les models/settings helps me to get better results.

I will let you know if I manage to get better results. Btw what was your problem size (# 0f cells)and time step size and no of time steps?
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Old   May 12, 2005, 05:30
Default Re: LES fully developed channel flow
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Gem
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the size of the computational box is 7.85 (x), 2(y), 4.71 (z). the grid size is 64x82x82. no of time steps = 3,500 timesteps (3 flow through times) prior to setting up the data sampling for data statistics.
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