On the noise from turbomachinery and ducted fans—A review of prediction methods

Abstract

Noise reduction of turbomachines and ducted fans is a major issue in aeronautics, with regard to both environment of airports and passengers. From the theoretical point of view, it is the final result of a whole strategy, involving physical understanding as a starting point and modeling as a tool for searching low-noise solutions. This is true for generating as well as propagating mechanisms. Within that scope, a complete simulation of the whole acoustic process from source to observer is not necessary. A partial model easy to run and able to predict the right trends is enough. The paper is devoted to a state-of-the-art in prediction methods. A presentation is given of both analytical and numerical techniques understood as complementary tools. Limitations of the former and expected future developments of the latter are discussed, together with hybrid techniques coupling computational fluid dynamics for the definition of sources and analytical acoustics. Examples are taken in the literature, not only in connection to turbofan engines, but also to other rotating blade technologies involving rotors and stators. The specificities of each application are used as a guideline for the best-suited approach.