[msrinath80]

I believe that there will be no need to continue using the old liftDrag implementation in new 1.5-based solvers. Since v1.5 can natively compute the dimensionless force coefficients through functionObjects, it would be wise to validate the new approach.

[mgz1985]

hi srinath

can u please tell how to follow what u have mentioned in the above post. I am new to Linux and OpenFOAM. And have a decent command in C++.

I am trying to calculate the lift and drag for an airfoil in openfoam but cant find the tool to do so. I hope u can explain in detail what u mean above by this

'Since v1.5 can natively compute the dimensionless force coefficients through functionObjects, it would be wise to validate the new approach.'

Thanks

[ivanwhlau]

Hi, Srinath,
I am not sure how to do it through functionObjects.
Would you please give me some directions how to set up to calculate force coefficient?
Ivan

[ngj]

Hi Ivan and Mayank

Please look into the following thread, which goes through the functionObject for forces.

http://www.cfd-online.com/cgi-bin/Op...how.cgi?1/8402

Further there is a discussion on modifying the output files to ease the plotting procedure, which you might also find interesting.

Best regards,

Niels

[msrinath80]

Thanks for the link Niels :-)

[ivanwhlau]

Thanks, Niels

[malaboss]

Originally Posted by msrinath80

Good to know that it compiled without issues. The Drag/Lift computation was primarily done by Frank Bos. Search for his posts in this forum concerning Lift and Drag, you will find many useful threads.

PS: If you need to extract the Lift/Drag coefficients from the log file conveniently, using the foamLog command, you need to add the following 4 lines in your foamLog.db file (which is present in ~/OpenFOAM/OpenFOAM-1.4/bin)

#- Drag coefficient:
dragCoefficient/DragCoefficient = /DragCoefficient =

#- Pressure Drag coefficient:
pressureDragCoefficient/pressureDragCoefficient = /pressureDragCoefficient =

#- Viscous Drag coefficient:
viscDragCoefficient/viscDragCoefficient = /viscDragCoefficient =

#- Lift coefficient:
liftCoefficient/LiftCoefficient = /LiftCoefficient =

Hi all,
I just saw this post and wanted to use it.
You cannot print lift and drag coefficient values like that now, because in the log file they don't appear as "LiftCoeffcient" and "DragCoefficient" anymore.
You need to add :

#- Lift coefficient:
LiftCoefficient/Cl = /Cl =
#- Drag coefficient:
DragCoefficient/Cd = /Cd =

at the end of the file /opt/openfoam211/bin/tools/foamLog.db

If you hear me Srinath, thanks a lot !