inviscid drag

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Arthur Williams

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Aug 4, 2024, 2:14:26 AM8/4/24

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Hi Cory,

Thank you for making and maintaining this amazing tool. I noticed 'inviscid Fx' values I get from both traditional and flying wing examples are positive, whereas 'viscous Fx' values are negative. My understanding is that negative x force is a drag, as negative x is pointing backward. I do not understand why inviscid Fx has positive value which I believe is induced drag and should be negative. Could you please help me out on this? Thank you.

Cory Goates

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Aug 6, 2024, 1:40:10 PM8/6/24

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Hi Arthur

You're welcome!

So there is a difference between force in the x direction and drag. Note this is the body-fixed x force, not the wind x force, which is the same as drag. If you want to think of it in terms of a 2D section, we're talking about the difference between axial force and drag force, which are different unless you're at zero angle of attack.