Wing aspect ratio value seems not correct

[aidanjungo]

tigl/src/wing/CCPACSWing.cpp

Lines 661 to 667 in 59ae251

	// Returns the aspect ratio of a wing: AR=b**2/A=((2s)**2)/(2A_half)
	// b: full span; A: Reference area of full wing (wing + symmetrical wing)
	// s: half span; A_half: Reference area of wing without symmetrical wing
	double CCPACSWing::GetAspectRatio()
	{
	return 2.0*(pow_int(GetWingspan(),2)/GetReferenceArea(GetSymmetryAxis()));
	}

I am not sure I completely understand how the formula to calculate AR has been changed recently, but when I use 'get_aspect_ratio()' for wing 1 of the D150 i got 526.71 before this change the value was 9.4.

>>> aircraft_tigl.get_wing(1).get_aspect_ratio()
526.7133945257066

It seems to me that it use the wrong reference area for the wing in the AR formula

If we use:

AR = (Span**2)/4 / RefArea *2

Before I think it was:

>>> 33.91522073785017*33.91522073785017/4/61.162786877005146*2
9.40312121494867

But now it seems to be:

>>> 33.91522073785017*33.91522073785017/4.3676208338421665*2
526.7133945257066

[aidanjungo]

I just checked, if I change "x-z-plane" by "x-y-plane" for the symmetry of wing 1, it gives the correct value, so it seems that "get_aspect_ratio()" did not use the correct reference area projection to calculate the AR.

[rainman110]

Hi @aidanjungo . Thanks for pointing this out. I'll have a look, why this has changed. Which TiGL version have you been using before (which didn't have this bug)?

[aidanjungo]

I am not sure of which version I was using because I installed cpacscreator via Conda. But now, I feel that Tigl3 has been update but maybe not cpacscreator, is it correct?
I saw the function "get_half_span" has been replace by "get_wingspan" in Tigl3, but it seems it does not exist (yet) in cpacscreator.

[rainman110]

Indeed, we have not updated cpacs creator yet. It still uses tigl 3.0.0 as a basis.

[rainman110]

I can reproduce this error. The error actually already existed in tigl 3.0.0.

The reason for the error is, that the wing reference area is computed incorrectly, because wrong projection planes are passed to the reference area computation.

[rainman110]

This test demonstrates the problem:
https://github.com/DLR-SC/tigl/runs/4152673156?check_suite_focus=true#step:25:1210

[rainman110]

Apparently, Malo fixed the bug back then in the cpacs creator. I'll backport the fix into tigl.