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Not getting vortex shedding behind square cylinder

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Old   March 23, 2006, 07:27
Default Not getting vortex shedding behind square cylinder
  #1
Hari
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I am working on flow around square cylinder using Fluent. First I got steady state solution using ske model. Then I switched to Unsteady with time interval 1/20 of expected shedding period. I am not getting periodicity in the contours of vorticity or static pressure. Anybody help me in this regard.
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Old   March 25, 2006, 05:52
Default Re: Not getting vortex shedding behind square cyli
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Muhammad Shakaib
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You can try laminar-unsteady model.
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Old   March 26, 2006, 23:57
Default Re: Not getting vortex shedding behind square cyli
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Hari
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Thanks Muhammad

I tried using laminar-unsteady model following the steps given in tutorial for a circular cylinder given in studentfluent.com. But still I am not getting the vortex shedding when I use sk-e(2d) with standard wall functions.

Thanks once again.

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Old   March 27, 2006, 03:22
Default Re: Not getting vortex shedding behind square cyli
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alex marshall
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then ask fluent engineer
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Old   March 28, 2006, 12:48
Default Re: Not getting vortex shedding behind square cyli
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Jeffery822
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You should make the mesh very fine. It works for me.
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Old   March 30, 2006, 00:35
Default Re: Not getting vortex shedding behind square cyli
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Hari
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Thanks Jeffery822,

Initially my mesh included 12000 cells. I tried with 60000 cells now. But after few 100 time steps, the lift coef. converges/stabilises to 0. I feel I might be doing something wrong at basic level. Here are my problem details:

1) b = 0.06m; U = 5.356 m/s with 2% turbulence intensity; Fluid = Air; So Re=22,000 2) problem domain is 21b in streamwise direction and 15b in other direction. 3) Standard k-e model, Standard wall functions with first node from wall being at 0.02b 4) Time step 0.004 s (i.e. (1/20) of shedding period of 0.08 s) 5) Velocity inlet, Pressure outlet and periodic boundary conditions 6) Applied a patch of Y-velocity equal to 1m/s and -1m/s in the top and bottom regions of wake, respectively.

Could please throw some light becasue you mentioned that the problem worked for you.

Thanks once again

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Old   April 12, 2006, 05:54
Default Re: Not getting vortex shedding behind square cyli
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sujay
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you will get ...contact me later
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Old   April 12, 2006, 08:14
Default Re: Not getting vortex shedding behind square cyli
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Hari
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Thanks Sujay.

I did get the vortex shedding when I reduced the eddy viscosity ratio at velocity inlet boundary.

You can post any further technical information in this regard.

Thanks once again.

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