Regarding Moment coefficients in .polar file

[Srinidhi NS]

Hi Rob, Hi All

In the polar file from VSP v3.45.2, I see only 3 moment coefficients (CMx, CMy, CMz), whereas earlier versions had 6 (body(CMx,CMy,CMz) + wind axis(CMl,CMm,Cmn)). Are these now all in the body axis, and why were the wind-axis moments removed?

Also, could you clarify what the “stall factor” in the polar file refers to?

Best regards,

Srinidhi 

[Rob McDonald]

You'll want to go back and check, but I'm pretty sure the body and wind axis moments were exactly equal in the old version -- wind was just an alias for body.

The stall factor is an adjustment in the new formulation to limit the local lift coefficient.  If a local section would normally produce a 2d cl greater than the specified clmax, then the circulation is reduced by the stallfactor such that the local cl is equal to cl.  This is adjusted in the fundamental solution of the flowfield.

This is really a local (spanwise varying) quantity, I'm not sure how the value reported in the polar file is calculated -- most likely some sort of average.

Rob

[Srinidhi NS]

Hi Rob,

Thanks for your prompt response.

Regards,

Srinidhi