The next generation of civil transport aircraft is required to have a significantly lower emission than the current aircraft to address the severe problem of climate change. To achieve this goal, various technologies and aircraft configurations are suggested to be integrated. Electric/hybrid-electric propulsion systems, active flow control, active load alleviation, and novel configurations such as blended wing body are currently being investigated. Ultra-High Aspect Ration Wings (UHARW) are promising solutions for reducing aircraft-induced drag, and hence reducing emissions. However, designing aircraft with UHARW faces serious challenges since increasing the aspect ratio negatively influences the wing structural weight and aeroelasticity.
The RHEA project is investigating intelligent solutions for escalating the TRL of UHARW for civil transport aircraft. The solution of RHEA is to integrate novel airframe technologies, i.e. active laminar flow control, active load alleviation, advanced structures and materials with novel aircraft configurations, i.e. strut-braced wing and twin fuselage. However, the design of aircraft with novel configurations and novel technologies required novel design methodologies and tools. Therefore, RHEA is aiming to develop beyond state-of-the-art methods and tools to design novel aircraft with disruptive configurations and novel airframe technologies and investigate the influence on reducing emissions and noise.
A numerical framework for MDO as well as modelling methodologies for coupled aero-structural mid-fidelity aircraft design were developed and implemented, including a higher-order correction method to account for nonlinear aircraft aerodynamics. The resulting 2-level MDO process was implemented and tested for the design of strut-braced wing (SBW) aircraft.
Based on this processes, different aircraft configurations were designed on a conceptual basis. Specifically, short-range, mid-range and long-range configurations were developed, each for a strut-braced wing configuration and for a twin-fuselage configuration. As based on these results a strut-braced wing concept does have potential for short-range configurations, whereas for mid or long ranges the twin-fuselage configurations showed slightly more potential.
In a final step, high fidelity evaluation tools, namely CFD and acoustics simulations based on scale-resolved flow fields, were used to analyse sensitivities and critical aspects. The analysis showed that the main sensitivities of a strut-brace wing are very similar to the ones of more conventional cantilever wing. For the aeroacoustics it was found out, that the major contributor from a strut-braced wing is the trailing edge noise from the strut, which is much larger than the noise generated near the attachment point of the strut on the wing.
