Are Alpha and Beta Coefficients Calculated Differently?

[Tristan]

Hello All,

I have been attempting to analyze vertical surfaces and their derivatives for a project I'm working on. I started out by placing a wing vertically and doing a beta sweep on it, assuming this would give lateral derivatives. However, this analysis was creating strange results. 

To do a sanity check I created a very simple wing (b=4, c=1, un-tapered, NACA 0010 foil) and did a sweep through -5 - 5 deg AoA. I then rotated the wing 90 degrees and did a sweep through -5 - 5 deg beta. While the force coefficient values stayed consistent through the rotation (I mainly considered the lift/side force), the coefficient of moment (CMy for horizontal and CMz for vertical) were different. After a bit of playing around, it looks like the coefficient of moment is divided by the Aspect Ratio when the model is rotated 90 deg. I.e. CMz(vertical run) = CMy(horizontal run) / AR.

Is there a methodology here for calculating lateral vs. longitudinal coefficients that is standardized? If someone could point me to how these coefficients are calculated that would be great! I would also like to know if any other variables are calculated differently if the model is rotated 90 deg.

[Rob McDonald]

Roll and yaw moments are normalized by bref.  Pitch derivatives are normalized by cref.

CMx = Mx / (0.5*Sref_*Bref_*Vref_*Vref_); // Roll
CMy = My / (0.5*Sref_*Cref_*Vref_*Vref_); // Pitch
CMz = Mz / (0.5*Sref_*Bref_*Vref_*Vref_); // Yaw

Rob

--
You received this message because you are subscribed to the Google Groups "OpenVSP" group.
To unsubscribe from this group and stop receiving emails from it, send an email to openvsp+u...@googlegroups.com.
To view this discussion on the web visit https://groups.google.com/d/msgid/openvsp/13220f87-9abc-4b62-b998-1e1b2eeaf905n%40googlegroups.com.

[Tristan]

Thanks Rob!

That clears things up.