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-   -   3D cylinder and Vortex Street shedding issues (http://www.cfd-online.com/Forums/fluent/71407-3d-cylinder-vortex-street-shedding-issues.html)

josik_1982 December 30, 2009 19:57

3D cylinder and Vortex Street shedding issues
 
Hello everyone,

I am a college student learning Fluent for a fluid mechanics class. as part of my final project for the class I am looking into Karman vortex streets of laminar flow past a cylinder.

I have already gone through the tutorial in 2D and the outcome has been as expected. now i am trying to run the scenario in 3D but there is no sign of vortex shedding when I do.

Cylinder diameter: 0.03m, Cylinder centered at 0,0,0 , cylinder extruded along the Z axis 0.03m in the positive and negative Z direction
Fluid enclosure 0.4m in front, 2m on each of the sides and 1.7m behind the cylinder.

fluent setup
Laminar flow, Velocity inlet of 0.15 m/s in the X direction of 1, the standard air settings for density and viscosity. PISO, Least square method, standard pressure, 2nd order upwind momentum.

my calculations show that with the Re=300 the time step is .034 with the St=0.2. the number of time steps is set to 1500 and 50 iterations per time step.

I have also tried the setup at Re=150 and double the time step. (this is the same setup used for the 2D scenario which worked fine).

I have done some research online regarding flow around a sphere which showed that shedding occurs at Re=300 and only after 480 seconds of the run. I have not waited that long since the Cl goes up to a point and then levels off and does not show the sinusoidal curve as seen in the 2D version. I have tried adjusting the mesh, geometry, Re numbers, going from least squared to Gauss green cell based. Still no luck seeing signs of shedding.

I have a few more options based on research I have done which I plan on trying, but any help pointing me in the right direction would be great.

I know this has been a long post, but have been trying to give as much information as I could. there is more to my project outside of just the vortex street, but I don't want to move ahead unless I get this part to work, taking a step by step approach. and for those interested, yes the semester is over but I took an incomplete so that i could finish the project. would rather be late and understand the material.

If there is any more info needed, please let me know, I will supply.

Thank you in advance and have a happy & healthy new years

csvirume July 9, 2010 15:35

i am not able to attach file . i am intened to provide you for guidance.

kepeng July 17, 2010 10:19

You could refer to this paper:
http://dspace.dsto.defence.gov.au/ds...-2232%20PR.pdf


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