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## Summary:

- Are these formulas for lift and drag correct ?

## Main Question or Discussion Point

Hi,

I have a simple question but I want to be 100% sure that my reasoning is correct. Take a look at this picture showing forces acting on an airfoil:

Green forces (X and Y components) are known from CFD software but I need the values of blue components (lift and drag). Of course for zero angle of attack they will be equal to each other but I need formulas for nonzero angle. In the literature I've found the following equation for lift: $$F_{L}=F_{X} \sin{\alpha} - F_{Y} \cos{\alpha}$$ From this I figured out the formula for drag: $$F_{D}=F_{X} \cos{\alpha} + F_{Y} \sin{\alpha}$$ Are these equations correct ? If not then how they should look like ?

Thanks in advance for your help

I have a simple question but I want to be 100% sure that my reasoning is correct. Take a look at this picture showing forces acting on an airfoil:

Green forces (X and Y components) are known from CFD software but I need the values of blue components (lift and drag). Of course for zero angle of attack they will be equal to each other but I need formulas for nonzero angle. In the literature I've found the following equation for lift: $$F_{L}=F_{X} \sin{\alpha} - F_{Y} \cos{\alpha}$$ From this I figured out the formula for drag: $$F_{D}=F_{X} \cos{\alpha} + F_{Y} \sin{\alpha}$$ Are these equations correct ? If not then how they should look like ?

Thanks in advance for your help