# Not getting vortex shedding behind square cylinder

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 March 23, 2006, 08:27 Not getting vortex shedding behind square cylinder #1 Hari Guest   Posts: n/a 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.

 March 25, 2006, 06:52 Re: Not getting vortex shedding behind square cyli #2 Muhammad Shakaib Guest   Posts: n/a You can try laminar-unsteady model.

 March 27, 2006, 00:57 Re: Not getting vortex shedding behind square cyli #3 Hari Guest   Posts: n/a 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.

 March 27, 2006, 04:22 Re: Not getting vortex shedding behind square cyli #4 alex marshall Guest   Posts: n/a then ask fluent engineer

 March 28, 2006, 13:48 Re: Not getting vortex shedding behind square cyli #5 Jeffery822 Guest   Posts: n/a You should make the mesh very fine. It works for me.

 March 30, 2006, 01:35 Re: Not getting vortex shedding behind square cyli #6 Hari Guest   Posts: n/a 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

 April 12, 2006, 05:54 Re: Not getting vortex shedding behind square cyli #7 sujay Guest   Posts: n/a you will get ...contact me later

 April 12, 2006, 08:14 Re: Not getting vortex shedding behind square cyli #8 Hari Guest   Posts: n/a 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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