|
[Sponsors] |
December 28, 2012, 04:49 |
drag coeficient
|
#1 |
New Member
Joaquim Monteiro
Join Date: Dec 2012
Posts: 12
Rep Power: 13 |
Hi,
How can I calculate the drag coeficient of a circular cylinder? Thank's |
|
December 28, 2012, 08:30 |
|
#2 |
Senior Member
Ehsan
Join Date: Oct 2012
Location: Iran
Posts: 2,208
Rep Power: 26 |
hi
Search at this site.i saw a comlete thread about lift and drag cefficients here. Be successful. |
|
January 5, 2013, 07:38 |
|
#3 |
New Member
Matthias K.
Join Date: Oct 2012
Location: Germany Erlangen
Posts: 20
Rep Power: 13 |
Hi,
You have to insert the function forceCoeffs into your control.dict. in the folder system. Here is a example: forceCoeffs { type forceCoeffs; functionObjectLibs ("libforces.so"); patches (patchname); //change to your patch name of the cylinder pName p; UName U; rhoName rhoInf; rhoInf 1.225; //Density of the fluid CofR (0 0 0); liftDir (0 0 1); dragDir (1 0 0); pitchAxis (0 1 0); magUInf 0.0243243243; //velocity lRef 0.0555; //reference length for forces Aref 1.11e-3; //reference surface of the cylinder outputControl timeStep; outputInterval 10; //every x timesteps =>one drag coefficient } Then you are able to calculate the drag coeficients Hope that helps Regards, Matthias |
|
January 6, 2013, 05:06 |
|
#4 |
New Member
Joaquim Monteiro
Join Date: Dec 2012
Posts: 12
Rep Power: 13 |
Thanks Matthias,
I'm a newbie in OpenFoam. I try and it works. Now the problem is that the value of cd is too high in compare with the academics work there i saw. Perhaps you know what's my problem. |
|
January 6, 2013, 07:44 |
|
#5 |
New Member
Matthias K.
Join Date: Oct 2012
Location: Germany Erlangen
Posts: 20
Rep Power: 13 |
Hi,
Is your case LES or RAS? Have you modified a existing tutorial? Have you checked your boundary conditions? Can you upload your case, that i can have a look? I am doing LES cd calculations of a 2d cylinder, at the moment. http://www.cfd-online.com/Forums/ope...questions.html Regards Matthias |
|
January 7, 2013, 04:54 |
|
#6 |
New Member
Joaquim Monteiro
Join Date: Dec 2012
Posts: 12
Rep Power: 13 |
Hi Matthias,
My case is RAS, The cd is too high, Can you take a look? Thanks |
|
January 9, 2013, 17:30 |
|
#7 |
New Member
Matthias K.
Join Date: Oct 2012
Location: Germany Erlangen
Posts: 20
Rep Power: 13 |
Hi,
I think your epsilon value is too high. Your value is 1.01. With a viscosity of 1e-3 and a velocity of 0.2 m/s is should imho be much smaller. Regards Matthias |
|
January 21, 2013, 09:14 |
|
#8 |
New Member
Matthias K.
Join Date: Oct 2012
Location: Germany Erlangen
Posts: 20
Rep Power: 13 |
Hi,
Have you solved the problem? |
|
January 22, 2013, 04:13 |
|
#9 |
New Member
Joaquim Monteiro
Join Date: Dec 2012
Posts: 12
Rep Power: 13 |
hi,
i can't solve the problem. now I'm in exams, and I haven't been working on the problem. you got see any errors in my files. thanks |
|
|
|
Similar Threads | ||||
Thread | Thread Starter | Forum | Replies | Last Post |
Pressure drag, friction drag and total drag? | Cheng | CFX | 9 | January 26, 2024 13:46 |
Incorrect Drag and Drag Coefficient for flow over a cylinder | ozzythewise | Main CFD Forum | 8 | June 13, 2012 06:24 |
Calculation of Drag Coefficient, Help Please | teek22 | CFX | 1 | April 26, 2012 18:41 |
problem with drag coeficient | yann | FLUENT | 1 | May 11, 2004 06:07 |
Inviscid Drag at subsonic, subcritical Mach # | Axel Rohde | Main CFD Forum | 1 | November 19, 2001 12:19 |