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I have implemented a nonlinear lifting line method to estimate lift/induced drag of a typical wing. This method utilizes 2D lift coefficient data, and uses a numerical technique to solve the nonlinear equations.

The program I have written in MATLAB is working, though I would like to confirm one key aspect of the results.

When I run the program for a swept back wings, I see that the induced angle of attack goes to negative towards the wing tip (aeff = a(geometry) - a(induced)).

From what I understand, towards the tip a wing, the local angle of attack there is greater than the freestream angle of attack, due to the induced flow, therefore a(induced)should be negative.

So my question is: Is getting a negative value for the induced angle of attack actually correct? I have a hard time trying to grasp this physically.

sample data induced angle of attack at the wing tip

0.024249058497046 (Close to wing tip)

-0.051359819152125

-0.088120053792167

-0.019725856790100

0.457096103863267 (wing tip)

Any help would be much appreciated.

Thank you.

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# Nonlinear Lifting Line method to estimate wing lift distribution

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