# Flow around circular cylinder

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 January 8, 2009, 15:13 Flow around circular cylinder #1 Karen Guest   Posts: n/a Dear all, I have been playing with Fluent a little recently and have been trying to replicate flow around a circular cylinder for Re of 200, 500, 1000. When comparing with experimental data, I notice that the trend in drag coefficient given by the simulation for increasing Re is opposite to that given by the experiment. I have followed fluent's own example for setting up low Re flow around a cylinder. Both pressure and momentum are second order. Pressure velocity coupling is PISO with the skewness-neighbor unchecked (again following Fluent's example). The fluid in question is water. Anyone have any suggestion as to why this may be occuring?

 January 9, 2009, 13:47 Re: Flow around circular cylinder #2 John S. Guest   Posts: n/a Differences could be due to the type of turbulence model you're running as well as grid around the cylinder.

 January 9, 2009, 14:25 Re: Flow around circular cylinder #3 Karen Guest   Posts: n/a At Re < 1000 it was my understanding that a turbulence model was not needed. Basically, according to literature, for this Re range, CD should be decreasing. With my simulations, CD is increasing (slightly).

 December 8, 2012, 23:35 flow around cylinder #4 New Member     Rishitosh Ranjan Join Date: Dec 2012 Location: Trichirapalli, Tamilnadu, India Posts: 18 Rep Power: 4 hiii.. i m also new in dis CFD area... i m working on flow over two side by side cylinders... @ Re= 100 and 200.. i got good results.. but i want to find out Strouhal number for all cases... i came to know by finding shedding frequency with help of FFT, using cofficient of lift data, in fluent 13.0 we can calculate Strouhal number... but i m getting helpess.. how to use FFT to find shedding frequency....????? -Rishi

December 11, 2012, 13:57
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Lucky Tran
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Quote:
 Originally Posted by rishitosh how to use FFT to find shedding frequency....????? -Rishi
FFT will give you amplitudes of oscillation for corresponding frequencies. You just need to look at the plotted FFT and notice which frequency has the highest amplitude. That amplitude should be the shedding frequency.

December 12, 2012, 11:34
inviscid compressible flow over cylinder
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wesam
Join Date: Sep 2012
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Hi

i have a problem with negative Cd.

i want to know where is a mistake.

i am in trouble please i need help

thank you
Attached Images
 Cd conv.jpg (66.3 KB, 10 views) Untitled.jpg (103.9 KB, 11 views) scale Grid.jpg (86.8 KB, 8 views) pressure Far-Field.jpg (93.9 KB, 5 views) operating condition.jpg (80.1 KB, 5 views)

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