Question on the calculation of lift coefficient
 

Hi all. The lift coefficient (also drag coefficient) is defined in the form of $C_L=\dfrac{F}{0.5\rho U^2A}$. And my question is in the post-processing step to calculate these coefficients, $A$ should be the sum of the areas of all mesh interfaces related to viscous wall, or it is a pre-defined valued given by the experiments. Many thanks.

It's a defined reference area, depends on the experiment, but there are some common ones (like projected wing area). What you described is wetted area, which is also used at times.

Many thanks for your reply. I found that in some test cases $A$ is provided as reference value, maybe some type of projected area.