Invicisd compressible flow over cylinder 2D

wesam · December 1, 2012, 18:47

hi

i have a problem in negative values of CD.

Images are shown for the solution process.

Please see the pic.

thank you

-mAx- · December 4, 2012, 03:12

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

wesam · December 4, 2012, 13:52

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

-mAx- · December 5, 2012, 01:12

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)

wesam · December 10, 2012, 18:39

thank you MAX

please check your e_mail.

I am in trouble
you only one can help me.

thank you

-mAx- · December 11, 2012, 01:31

Quote:

Originally Posted by wesam

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

December 4, 2012, 03:12		#2
-mAx- Super Moderator Maxime Perelli Join Date: Mar 2009 Location: Switzerland Posts: 3,297 Rep Power: 41	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 __________________ In memory of my friend Hervé: CFD engineer & freerider

December 5, 2012, 01:12		#4
-mAx- Super Moderator Maxime Perelli Join Date: Mar 2009 Location: Switzerland Posts: 3,297 Rep Power: 41	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) wesam likes this. __________________ In memory of my friend Hervé: CFD engineer & freerider Last edited by -mAx-; December 5, 2012 at 01:29.

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December 10, 2012, 18:39		#5
wesam New Member wesam Join Date: Sep 2012 Posts: 23 Rep Power: 13	thank you MAX please check your e_mail. I am in trouble you only one can help me. thank you