Flow induced noise is an important environmental aspect of both ground and air vehicles. For air transportation in particular noise emission around airports is of growing importance, mainly because of increasing air traffic and because of rapid expansion of housing developments in the vicinity of airports. Although quite dramatic reductions in aircraft noise have been achieved during the last decades, the legislative pressure for further noise reductions remains high. Cost incentives for quiet aircraft are currently in effect at most airports, and some of the bigger ones have even introduced 'hard' noise limits. This means that the airframe and aero-engine manufacturers are hard pressed by their customers to deliver aircraft, which fulfill both international and local regulations on noise emissions. Noise reduction can be achieved either by modifications that eliminate the noise source or by suppression of the noise already generated by the means of acoustic liners. Acoustic wall treatment has been used for quite a long time but lately aero-engine manufacturers and researchers within the aero-acoustic community have shown growing interest for improved liner technology and liner impedance modeling. Also, the complexity of liner installations is constantly increasing.
In order to be able to develop efficient numerical models for simulation of the effect of acoustic liners under engine realistic conditions, detailed investigation of the liner physics is needed. Especially for liners operating under grazing flow conditions. In this project project detailed numerical simulations will be used to gain understanding on the liner physics under such conditions.
In the H2020 project ULTIMATE, next generation aero engine architectures will be designed on a conceptual level. One of the studied is the open rotor configuration that has gained interest the last decade. One of the main drawbacks of the open rotor concept is the sound generation and therefore detailed aeroacoustic analysis of the concept will be done as part of the ULTIMATE project.