[andrea.valletta2590@gmail]

Dear all,
I wish to investigate the interaction between a front wing and the adjacent wheel. I need to evaluate the Cd and Cl of both elements, but I don't know how to input the reference values which are necessary to compute the aforementioned coeffiecients. I hope you can help me, I have looked on the forum but I was quite unsuccesful to find a solution.
Thanks in advance

[LuckyTran]

The reference values are defined per the definition of drag and lift coefficient.
You should use input the values required by YOUR definition. See also:

http://en.wikipedia.org/wiki/Drag_coefficient
http://en.wikipedia.org/wiki/Lift_coefficient

As for where to specify these reference values, they go in the reference values pane in the GUI.

[andrea.valletta2590@gmail]

Ok thank you LuckyTran, but in the case of a wing with two elements, where the second one doesn't have the same longitudinal length of the first one, what would be the length to input in "reference values"? The area is ok, I think I should input the plane area.
One more question: in the case I wished to simulate the interaction of a front wing for racecars with a wheel and I were interested in knowing both the drag of the wing and of the wheel, what 'length' and 'area' should I input? I am quite confused since each object, the wing and the wheel, would have its own length and area, but I am allowed to input only one value and in the post-processing I can measure the aero-parameters separately though

[`e`]

You could enter unity for area and length reference values and then scale accordingly for the separate geometries in postprocessing.

[LuckyTran]

Originally Posted by andrea.valletta2590@gmail

Ok thank you LuckyTran, but in the case of a wing with two elements, where the second one doesn't have the same longitudinal length of the first one, what would be the length to input in "reference values"? The area is ok, I think I should input the plane area.
One more question: in the case I wished to simulate the interaction of a front wing for racecars with a wheel and I were interested in knowing both the drag of the wing and of the wheel, what 'length' and 'area' should I input? I am quite confused since each object, the wing and the wheel, would have its own length and area, but I am allowed to input only one value and in the post-processing I can measure the aero-parameters separately though

At the analysis level, there should never be any confusion over the reference length and area. Maybe if you have never seen drag and lift coefficient before or it is your first day in school.

I always coach people that the reference length and area are defined during the definition of drag and lift coefficients. Once you have accepted a specific definition for lift and drag coefficients then you have committed to a reference length and area and you must use these.

e suggested and good way to proceed, use unity reference lengths and area and do the post-processing elsewhere. However, you should never have to ask anyone what the reference length or area is. The only valid question is, how do you define lift and drag coefficient?