Result interpretation

[Mike Vivaldi]

Hey All,

I've been looking through the new VSPAERO results and had a question. When examining the polar file, is the aircraft total C values computed by adding the C[]tot for surface and C[]wtot for wake?

Thanks,

Mike

[Rob McDonald]

There are a bunch of related coefficients with different subscripts.  This has changed somewhat from earlier versions.  In the version of VSPAERO shipped with 3.45.X and newer,

CLo    -- parasite contribution to lift coefficient
CLi     -- inviscid contribution to lift coefficient, calculated from Biot Savart summation of vortex loops
CLtot -- CLo + CLi
CLwtot -- CLo + CLiw
CLiw   -- inviscid contribution to lift coefficient, calculated from a summation of vorticity in the wake

CLi can be thought of as a surface integral -- but it is not a surface integral of Cp.

CLiw can be thought of as a wake integral -- similar to a Trefftz plane approach.

In general, the wake formulation will converge sooner than the surface integral approach and will usually be more accurate.  However, it has limitations.  For example, it can not be used to calculate moments.

Rob