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MIT-LAE / TASOPT.jl

Medium fidelity aircraft-propulsion system design and optimization.
https://mit-lae.github.io/TASOPT.jl/
MIT License
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Inconsistency in fuselage cross-section definition of the number of webs and bubble center offsets #61

Closed askprash closed 1 month ago

askprash commented 3 months ago

Fundamentally there is an inconsistency in how the number of fuselage webs (nfweb) for multi-bubble fuselages and the y-offset of the bubble centers (wfb) are being treated. If it is a single bubble then wfb = 0.0 and nfweb = 0. However, the default inputs (which mainly showcase single-bubble) designs are all inconsistent as they set nfweb = 1. This seems to be a bug carried over from the FORTRAN code v2.16 where getparams.f hardcodes nfweb = 1.0. While this is harmless in some parts: https://github.com/MIT-LAE/TASOPT.jl/blob/dc5e481d8417c60182e6ed5660f46c3b6aa9370f/src/structures/fuseW.jl#L159-L164

since wfb=0.0 here means it doesn't matter what nfweb is. However, it does mess up the calculation here: https://github.com/MIT-LAE/TASOPT.jl/blob/dc5e481d8417c60182e6ed5660f46c3b6aa9370f/src/structures/fuseW.jl#L300-L304 nfweb = 1 leads to a wrong x-moment of inertia here (second term should be zero if single bubble).

A cleaner setup that avoids confusion is to specify the number of bubbles in the input and appropriately perform some checks before constructing the fuselage structures.

I'm addressing this as part of the updates and clean-up in #57, but all the default sizing outputs in the tests will need to change ever so slightly.

ngomezve commented 2 months ago

Good realization! I also noticed that N_webs = 1 in the inputs seemed odd for single-bubble aircraft.

askprash commented 1 month ago

Addressed by #57