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Old   January 8, 2009, 15:13
Default Flow around circular cylinder
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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?
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Old   January 9, 2009, 13:47
Default Re: Flow around circular cylinder
John S.
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Differences could be due to the type of turbulence model you're running as well as grid around the cylinder.
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Old   January 9, 2009, 14:25
Default Re: Flow around circular cylinder
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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).
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Old   December 8, 2012, 23:35
Question flow around cylinder
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Rishitosh Ranjan
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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....?????
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Old   December 11, 2012, 13:57
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Originally Posted by rishitosh View Post
how to use FFT to find shedding frequency....?????
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.
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Old   December 12, 2012, 11:34
Default inviscid compressible flow over cylinder
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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
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File Type: jpg Untitled.jpg (103.9 KB, 11 views)
File Type: jpg scale Grid.jpg (86.8 KB, 8 views)
File Type: jpg pressure Far-Field.jpg (93.9 KB, 6 views)
File Type: jpg operating condition.jpg (80.1 KB, 6 views)
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