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-   -   Drag Coefficient (http://www.cfd-online.com/Forums/fluent/100300-drag-coefficient.html)

James Hetfield April 23, 2012 15:17

Drag Coefficient
 
Im trying to find the drag coefficient for NACA0012
Although I have a really fine mesh, it doesnt converge and at best it gives me 50% off the experimental data
why is it like this?

LuckyTran April 23, 2012 22:58

Quote:

Originally Posted by James Hetfield (Post 356470)
Im trying to find the drag coefficient for NACA0012
Although I have a really fine mesh, it doesnt converge and at best it gives me 50% off the experimental data
why is it like this?

You should focus on the problem of convergence beforehand. You shouldn't expect any meaningful results if the solution has not reached any type of convergence. If you give some details of how you're modelling it then maybe we can come up with reasons why it is not converging. Things like y+, turbulence models used, wall function approach, discretization scheme, etc etc. Give details if you want help!

If the solution had converged then I would have said, for Drag Coefficient

What is 50% off? Is it the drag coefficient?

Did you remember to set your reference values? You need to specify the reference density and velocity for the dragon coefficient. For force vector you also need to input the reference vector. Other coefficients use other reference values also.

James Hetfield April 24, 2012 13:01

although my mesh is fine (starts from 1e-06 normal to the airfoil surface) I dont reach convergence :(
what is wrong with it?

LuckyTran April 24, 2012 16:45

Quote:

Originally Posted by James Hetfield (Post 356704)
although my mesh is fine (starts from 1e-06 normal to the airfoil surface) I dont reach convergence :(
what is wrong with it?

Can you give any other details about the simulation? And wth is 1e06? How big is your airfoil? Anything? Give details!

James Hetfield April 24, 2012 21:21

1e0-6 is the distance of first layer from the airfoil
the chord is 1 meter

Im using C-mesh

Im trying to use SA or SST-KW for turbulence model but i cant get convergence :(

give me email so i cant send u "tin" file

LuckyTran April 24, 2012 21:53

Quote:

Originally Posted by James Hetfield (Post 356767)
1e0-6 is the distance of first layer from the airfoil
the chord is 1 meter

Im using C-mesh

Im trying to use SA or SST-KW for turbulence model but i cant get convergence :(

give me email so i cant send u "tin" file

1e-6 astronomical units?

James Hetfield April 24, 2012 21:58

1e-06 meter


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