- BMW Rolls-Royce GnbH
- Rolls-Royce plc
- National University of Ireland
- Kungliga Tekniska Högskalan, MWL
- Institute of Sound and Vibration Research
In the first phase of this project a boundary element formulation for modelling the sound field inside and outside a duct placed in a uniform flow was developed. The model was the first step towards the development of models for predicting the noise radiated from turbo fan engines. For this purpose the frequency range of interest is very large (up to ka=40), and an axisymmetric formulation has been developed in order to minimise the computational work. Non-axisymmetric excitation is important in fan noise predictions (spinning modes), and thus the model has been extended to allow for spinning modes. The model allows the duct to be partially or fully treated with an axisymmetric locally reacting liner. The model calculates the sound field inside and outside the duct simultaneously, and the results are presented in terms of a modal expansion inside the duct and a directivity pattern outside the duct. The results of the model has been compared with results from the literature and from a semi-analytical model developed by NLR. Good agreement has been found in the entire frequency range of interest. The purpose of the second phase of the project is to develop a similar boundary element model that can take account of a potential flow. This work is still in an initial phase; at present calculations of scattering of sound fields by hard bodies in the presence of potential flow have been validated. The work is based on a transform technique that is valid for Mach numbers up to 0.3.
|Period||01-02-98 → …|
|Amount||1,500,000.00 Danish kroner|