|
[Sponsors] |
December 1, 2012, 18:47 |
Invicisd compressible flow over cylinder 2D
|
#1 |
New Member
wesam
Join Date: Sep 2012
Posts: 23
Rep Power: 13 |
hi
i have a problem in negative values of CD. Images are shown for the solution process. Please see the pic. thank you |
|
December 4, 2012, 03:12 |
|
#2 |
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 4, 2012, 13:52 |
|
#3 |
New Member
wesam
Join Date: Sep 2012
Posts: 23
Rep Power: 13 |
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 |
|
December 5, 2012, 01:12 |
|
#4 |
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)
__________________
In memory of my friend Hervé: CFD engineer & freerider Last edited by -mAx-; December 5, 2012 at 01:29. |
|
December 10, 2012, 18:39 |
|
#5 |
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 |
|
December 11, 2012, 01:31 |
|
#6 | |
Super Moderator
Maxime Perelli
Join Date: Mar 2009
Location: Switzerland
Posts: 3,297
Rep Power: 41 |
Quote:
I don't have any email
__________________
In memory of my friend Hervé: CFD engineer & freerider |
||
|
|
Similar Threads | ||||
Thread | Thread Starter | Forum | Replies | Last Post |
compressible flow calculation error using rhoSimpleFoam solver | student4326 | OpenFOAM Running, Solving & CFD | 7 | November 2, 2015 11:34 |
Incorrect Drag and Drag Coefficient for flow over a cylinder | ozzythewise | Main CFD Forum | 8 | June 13, 2012 06:24 |
Producing a supersonic flow in a constant diameter cylinder | clgs.1903 | FLUENT | 12 | May 24, 2012 13:41 |
how to set BC for compressible flow target mass flow rate | foolboy007 | FLUENT | 1 | April 4, 2012 03:24 |
Can 'shock waves' occur in viscous fluid flows? | diaw | Main CFD Forum | 104 | February 16, 2006 05:44 |