All aeroengine manufacturers are committed to reducing aircraft noise over the next twenty years. Indeed, noise is seen as a major inhibitor to the growth of the aviation industry, with existing airports operating at full capacity and local communities objecting to airport or runway growth because of the intrusive effects of aircraft noise. The noise from the exhaust jet of a modern turbofan engine is the dominant component of aircraft noise at take-off and must be reduced if aircraft are to be made quieter. Historically, jet noise has been reduced, whilst maintaining engine thrust, by increasing the bypass ratio. However, this increases engine diameter and, since the practical limit on engine size has been reached, more subtle changes are now necessary that require insight into the fundamental physics of noise generation and propagation.
The aim of this research is to develop a unified model for jet noise, based rigorously on the equations of fluid motion, which gives good predictions for the sound radiated by a turbulent jet in a reasonable calculation time, and enhances understanding of the noise source mechanisms and how they can be modified. An acoustic analogy formulation is used, in terms of Green functions solving the adjoint linearised Euler equations from equivalent noise sources. These source terms are modeled using RANS for preliminary design and LES data to determine the large-scale flow structures for detailed engine design.
Collaborators and support
Loughborough University, California Institute of Technology, Rolls Royc.