Design methodology for an inflatable membrane aerofoil using numerical shape optimisation

Bezuidenhout, Bradley (2020-04)

Thesis (MEng)--Stellenbosch University, 2020.

Thesis

ENGLISH ABSTRACT: The use of inflatable wings for unmanned aerial vehicles over their fixed-winged counterparts has many advantages such as the wing’s ability to be folded up when deflated, this saves storage space. However, there are challenges associated with predicting the profile of the inflatable wing, which makes achieving a desirable aerofoil profile non-trivial. This research aimed to formulate a design methodology which would determine the uninflated geometry for an inflatable aerofoil profile, accurately fitting that of a target, prescribed aerofoil profile. The uninflated geometry can then be used to construct a physical model. The methodology involved performing numerical shape optimisation on finite element models. Once the methodology had been established, its robustness was tested by utilising numerical models with differing numbers of inflation cavities, altering the thickness of the target aerofoil profile as well as increasing its complexity. For each case, the methodology successfully satisfied its aim, producing accurate fits between the inflated numerical model and the target aerofoil profile. When fitting a fifteen cavity numerical model to a NACA 0030 aerofoil, an R2 fit of 0 .990 was achieved. When validated, the inflated shape of the numerical model proved to predict that of its corresponding physical model accurately. For an eight cavity model, the fit between the physical and numerical model produced an R2 value of 0.988. Future work should focus on a more comprehensive material model that will allow for a larger load-bearing capacity of the inflated structure.

AFRIKAANSE OPSOMMING: Die gebruik van opblaasvlerke vir onbemande lugvaartuie bo-oor die regstreeks gevleuelde weergawes het veelvulgide voordele. Daar is vele kompleksiteit in akkurate profiel voorspelling van opblaasvlerke, wat veroorsaak dat die bereiking van ’n gewenste lugvliegprofiel ontriviaal is. Die doel van die navorsing is gemik om die formulering van ’n ontwerpmetodologie wat die afgeblaasde meetkunde van ’n opblaasbare-aëroolieprofiel sou bepaal. Die afgeblaasde meetkunde kan dan gebruik word om ’n fisiese model te konstrueer. Die betrokke metodologie maak gebruik van numeriese vorm optimalisering op eind element modelle. Nadat die metodologie vasgestel is, was die robuustheid daarvan getoets deur die gebruik van numeriesemodelle van verskeie kompleksiteite, deur die dikte van die teiken lugvliegprofiel te verander en die kompleksiteit te verhoog. Vir elke getoetsde geval, het die metodologie sy doelwit bereik deur ’n akkurate pas tussen die opgeblaasde numeriesemodel en die teiken aëroolieprofiel. By die montering van ’n numeriese model van die vyftien holtes op ’n NACA 0030 aërool, word die R2 pas van 0.990 behaal. Na validasie, het die opgeblaasde vorm van die numeriesemodel met akkuraatheid die vorm van die fisiesemodel bepaal. Vir ’ n model met agt holtes is die pas tussen die fisiese en numeriese model geproduseer teen R2 waarde van 0.988. Toekomstige navorsing moet gebruik maak van ’n meer ingewikkelde model, wat sal toelaat vir ’n beter draëvermoë van die opgeblaasde struktuur.

Please refer to this item in SUNScholar by using the following persistent URL: http://hdl.handle.net/10019.1/107970
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