[kenya0514]

Hello

I encountered a problem when I am trying to do some calculation with XFOIL.

I did some measurements with an airfoil in a wind tunnel. And now, I would like to do some calculations with XFOIL using the same configurations as in the measurements.

Since XFOIL gives CL CD directly, I think it is necessary to know the type of fluid (in order to use the right \rho). How can I check that? Or is it possible to change the fluid type to air?

Maybe I am wrong...Please enlighten me. Thank you very much.

[onyir]

Hi,

When you use XFoil, if defining a viscuous calculation, you have to set the Reynolds number and Mach of the simulation. That's the only way you define your fluid, and it should be enought.

[kenya0514]

Thank you for your reply...

I still have some doubts...If the fluid type is only defined this way, how would XFOIL calculate CL CD? Since we need F/(0.5\rho U^2 S) to get CL CD, right?
Or does it calculate those another way?

Thank you

[whizkid]

Originally Posted by kenya0514

Thank you for your reply...

I still have some doubts...If the fluid type is only defined this way, how would XFOIL calculate CL CD? Since we need F/(0.5\rho U^2 S) to get CL CD, right?
Or does it calculate those another way?

Thank you

You dont have to know the fluid type. maybe you can check Drela's paper, Section 3. http://web.mit.edu/drela/Public/papers/xfoil_sv.pdf