Noise of future aircraft propulsion: sources and design considerations

This paper attempts to reduce the gap, when it comes to future aircraft concepts noise and aeroacoustics, and at the same time introduce basic noise aspects for people unfamiliar to it. This is performed by taking into account the following four stages: Identification of conventional aircraft noise sources, overview of the aeroacoustics of future aircraft configurations, derivation of conceptual design considerations for noise issues, and finally, insight on the impact of technology advancements on certification. More specifically, a holistic overview of the aeroacoustics of aircraft was performed. The noise sources were described and made available for those unacquainted with the subject. Aeroacoustic behavior of ContraRotating Open Rotors, Boundary Layer Ingestion and Distributed Propulsion concepts was studied trough the most recent and relevant literature. The phenomena causing noise were highlighted, and the differences between conventional and future designs detected. It was found that generally noise sources are similar, but the intensity of some can be significantly altered. Early design phase guidelines were extracted for each of the concepts. The design considerations are grouped into a matrix showing the relative effect of each on noise emissions. With these guidelines, it is possible to perform design choices in the conceptual level of fidelity for future aircraft concepts. Furthermore, certification aspects and observations considering its future development are presented. Noise emissions are expected to change, and thus certification must be adapted to it. Furthermore, in this quick advancing technology field, virtual certification is advised to be used.