The mitigation of noise generating mechanisms was achieved through novel technologies including porous materials, leading and trailing edge serrations, and over-the-tip liners. The aeroacoustic effect of rod vortex generators, initially designed to delay flow separation, was investigated as well. Noise can also be attenuated during propagation by means of porous liners, micro-perforate panels and active impedance control. Finally, the transmission of noise through flexible panels has been attenuated by means of architected metamaterials.
In terms of exploitation potential, the industrial partners of the project and those invited in the Advisory Board have provided precious recommendations as to the applicability of the technologies to their fields. About source mitigation, serrations are being implemented on wind turbines, automotive low-speed cooling fans and building ventilation systems. Other technologies such as porous materials, regarded as a promising avenue to reduce airframe noise, will require further research in order to meet the tight airworthiness conditions that apply in the aeronautical sector. In this sector, passive liners have been extensively used for some time already, but the novel technologies proposed in the project (over-the-tip liners, micro-slit systems and active liners) open interesting perspectives. Another innovative noise control technology, based on architected metamaterials to attenuate transmission, show great potential as well. It should be finally stressed that some of the simulation technologies developed in the project, such as domain decomposition techniques for acoustic simulations, and adjoint-based optimization techniques, will find many fields of application beyond the sectors that were already represented in SmartAnswer.
The research outcomes have been continuously disseminated throughout the project evolution, concluding with the organization of a dedicated Lecture Series and open public Workshop. The ESRs have been actively involved in those events for the preparation and delivery of formal lectures to a broad audience constituted by PhD students, young professionals and more established researchers in the various fields addressed by the project. A last and very important tool for dissemination and communication towards both scientific experts and a broader audience is an aeroacoustic demonstrator, jointly developed by the project partners. It consists in a miniature wind tunnel, which gathers all the noise mitigation technologies developed by the ESRs.
Finally, it should be stressed that all the training program, and most of the ambitious secondment programme have been delivered despite the adverse conditions related to the Covid pandemic, requiring only minor adaptations.
