Efficient field prediction strategies for aeroacoustic design optimisation of turbofan engine liners

This paper investigates the feasibility of applying a gradient based optimization algorithm to a frequency domain, finite element, aeroacoustics field method. The ultimate aim of the investigation is to optimise the impedance of an acoustic lining for reduced sound pressure level in the far field for a realistic turbofan inlet configuration. By their nature gradient based design methods use many aeroacoustic function evaluations in searching for the optimum. Such a procedure tends to be computationally expensive, especially for 3D radiation problems. To overcome this difficulty an iterative solution method has been developed which reuses the pre­conditioned global matrix of the finite element algorithm for repeated aeroacoustic analysis. The result is significant reduction in the computational time required for each aeroacoustic solution making this a practical method for use in the parametric study and design optimisation of liner configurations.