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Invicisd compressible flow over cylinder 2D

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Old   December 1, 2012, 19:47
Default Invicisd compressible flow over cylinder 2D
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wesam
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hi

i have a problem in negative values of CD.

Images are shown for the solution process.

Please see the pic.

thank you
Attached Images
File Type: jpg cylinder.jpg (96.9 KB, 25 views)
File Type: jpg Drag convergence.jpg (69.7 KB, 21 views)
File Type: jpg Negative cd solution.jpg (103.0 KB, 16 views)
File Type: jpg operating pressure.jpg (95.1 KB, 17 views)
File Type: jpg pressure Far-field.jpg (94.1 KB, 17 views)
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Old   December 4, 2012, 04:12
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Maxime Perelli
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your solution isn't converged (your second picture can prove it, since it is still oscillating)
disable the "check convergence" at 1e-3 and let iterate.
Just break the iterations once your cd has a constat value
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Old   December 4, 2012, 14:52
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HI MAX

i have done what you said to me.but the result of CD is negative and it is impossible it must be positive.(aerodynamic basic).

where is the error.
thank you Mr.MAX
Attached Images
File Type: jpg Untitled.jpg (66.7 KB, 6 views)
File Type: jpg cd.jpg (64.9 KB, 7 views)
File Type: jpg Untitled2.jpg (101.4 KB, 6 views)
File Type: jpg Residuals.jpg (92.7 KB, 7 views)
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Old   December 5, 2012, 02:12
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I don't know...
check if the velocity and pressure distribution are ok
Check also the forces on your 2d-cylinder and compute manually your Cd
And also check if your axis are well defined, especially the one for Cd should be in same direction as fluid is flowing (it is the only explanation for negative value, since others are positive)
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Last edited by -mAx-; December 5, 2012 at 02:29.
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Old   December 10, 2012, 19:39
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thank you MAX

please check your e_mail.

I am in trouble
you only one can help me.

thank you
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Old   December 11, 2012, 02:31
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Quote:
Originally Posted by wesam View Post
thank you MAX

please check your e_mail.

I am in trouble
you only one can help me.

thank you
did you post a thread?
I don't have any email
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