Applications of Finite Element and Wave Envelope Element Approximations to Turbofan Engine Noise Radiation Including Flight Effects

The problem of acoustic radiation from turbofan engine inlets in flow has not lent itself fully to analysis by numerical means because of the large domains and high frequencies involved. The current work has extended the use of finite elements and wave envelope elements, elements which simulate decay and wavelike behaviour in their interpolation functions, from the no-flow case in which they have been proven, to cases incorporating mean flow. By employing an irrotational mean flow assumption, the acoustics problem has been posed in an axisymmetric formulation in terms of acoustic velocity potential, thus minimising computer solution storage requirements. The results obtained from the numerical procedures agree well with known analytical solutions, static experimental jet engine inflow data, and also with flight test results.