[SteveFRUCD]

First post here, I've been having trouble getting reliable coefficients out of both 2D and 3D sims. I've been testing a simple NACA E591 airfoil to compare results to the database, and I'm seeing drag coefficients of .863 and lift of 60.3 when using an alpha of 0 at Reynolds of about 500,000. Strangely, the ratio between them is a little low but believable (~70). Also, I used the lift and drag forces from the 3D sim to calculate the coefficients by hand and they came out to .633 and .0367 which is far more believable, even with the drag being high. Am I using the coefficient reports tool incorrectly? Any help would be greatly appreciated!

[fluid23]

The coefficient reports can do some weird things. I have contacted the support staff about it in the past thinking it was a bug, but was informed that it was intentional. Basically, when calculating 2D coefficients, the reference area assumes a depth of 1m regardless of your unit system. For example:

1.8315m (chord length) x 1m (depth) = A for SI

or

6ft (chord length) x ‪3.28084ft (depth) = A for BG

I am not sure that will solve all of your problems, but it might help. You should also confirm the reference density and speed in the coefficient match your setup, use wake refinement options and conduct a mesh dependency study (if you haven't already).