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-   -   airfoil lift and drag coefficient (http://www.cfd-online.com/Forums/fluent/111192-airfoil-lift-drag-coefficient.html)

amir_14 December 31, 2012 06:03

airfoil lift and drag coefficient
 
hi dear friends
i have problem with modeling s809 airfoil
at low angle of attack i have large lift coefficient (200 times larger) and large negative drag coefficient & at high angle of attack i have large lift and drag coefficient.
also my pressure coefficient is large and inverse !:(

http://img4up.com/up2/12426092741833649440.jpg

can everybody help me?:(

cfd seeker December 31, 2012 12:45

Have you scaled the mesh in fluent? Show your mesh, solver settings, boundary conditions, turbulence model then I will be able to suggest you something

amir_14 January 1, 2013 06:21

Quote:

Originally Posted by cfd seeker (Post 399564)
Have you scaled the mesh in fluent? Show your mesh, solver settings, boundary conditions, turbulence model then I will be able to suggest you something

tanx dear cfd seeker
i found my mistake
it was at reference values
but my pressure coefficient is inverse still

amir_14 January 1, 2013 06:27

http://img4up.com/up2/95355975160838392917.jpg

http://img4up.com/up2/41789434038302271552.jpg

http://img4up.com/up2/62569138080709307790.jpg

http://img4up.com/up2/15325669415822876946.jpg

Sixkillers January 1, 2013 06:58

I think that the mesh has to be more finer in region of boundary layer to properly compute forces (drag/lift) acting on airfoil. What is your Y+? Have you consider usage of SST k-omega turbulence model?

amir_14 January 1, 2013 09:30

Quote:

Originally Posted by Sixkillers (Post 399611)
I think that the mesh has to be more finer in region of boundary layer to properly compute forces (drag/lift) acting on airfoil. What is your Y+? Have you consider usage of SST k-omega turbulence model?

hi Sixkillers
i've adapted mesh near the wall so that y+ is Between 2 and 5 with Spalart-Allmaras Model.


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