Lift Force

[bharswami]

In Matlab Tornado (or PyTornado) the total lift force is calculated across all surfaces or only the first wing? Is CL calculated using this lift force?

[aarondettmann]

Yes, the forces on all surfaces (wings, horizontal/vertical tail etc.) are summed up into a global force vector. This force vector is then transformed into the aerodynamic coordinate system to express lift, drag and the side force. A few more hints can be found here:

• https://pytornado.readthedocs.io/en/latest/theory/coordinate_systems.html
• https://pytornado.readthedocs.io/en/latest/theory/global_coeffs.html

In case you are interested in the code itself and potentially improving it, the summing of panel forces and transformation into the aerodynamic coordinate system is done here:

https://github.com/airinnova/pytornado/blob/0c88624e6a4f4629d136365c3aa8e31c2d538e73/src/lib/pytornado/aero/c_results.cpp#L38

[bharswami]

Thanks for your reply Aaron. I have a code that computes Lift and Drag for each panel. The freestream is in the negative x-direction. How to compute FX,FY,FZ,L,M,N.

On Sun, Dec 22, 2019 at 3:04 PM Aaron Dettmann notifications@github.com wrote:

Yes, the forces on all surfaces (wings, horizontal/vertical tail etc.) are summed up into a global force vector. This force vector is then transformed into the aerodynamic coordinate system to express lift, drag and the side force. A few more hints can be found here:

- https://pytornado.readthedocs.io/en/latest/theory/coordinate_systems.html

• https://pytornado.readthedocs.io/en/latest/theory/global_coeffs.html

In case you are interested in the code itself and potentially improving it, the summing of panel forces and transformation into the aerodynamic coordinate system is done here:

https://github.com/airinnova/pytornado/blob/0c88624e6a4f4629d136365c3aa8e31c2d538e73/src/lib/pytornado/aero/c_results.cpp#L38

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[aarondettmann]

PyTornado computes both global forces in the body-fixed coordinate system (Fx, Fy and Fz) as well as global forces in the aerodynamic coordinate system (FL, FD, FC). These two systems differ if angle of attack and/or side slip angle are non-zero (see). The transformation in PyTornado is implemented according to [1].

[1] Drela, M.: Flight Vehicle Aerodynamics. Cambridge, Massachusetts: MIT Press, 2014. -- ISBN 978-0-262-52644-9

[bharswami]

Thanks Aaron