Simulation numérique du contrôle acoustique actif appliqué au bruit d'un turboréacteur

Abstract
Jet engine technology in the years to come will focus on Ultra-High Bypass Ratio concepts (UHBR), i.e. low speed fan design associated with a relatively low-number of fan blades. A direct consequence will be an emphasis on low frequencies in the flyover noise signature, exactly where current "passive" noise reduction solutions tend to be less effective and exhibit serious limitations, not mentionning the ever shorter nacelle dimension associated with those new engine concepts. In the world where increasing noise limits stringency is more and more often considered as a way to reduce aircraft noise, engine manufacturers had to take real steps towards new noise reduction technology and as a consequence get interested in the potential applications of active noise control. Our prime objective is to be able to control the directivity of engine at low frequency radiation. Accordingly one of the ways, the goal is not to reduce the acoustical field in all the directions, but only in priviliged ones with the concentration of acoustical energy in a non inconvenient domain. To validate this concept, a numerical simulation technique has been set up. After a presentation of the method employed, priliminary results are analysed with and without simulated active noise control.