Advanced correlation criteria for the mid frequency range

Kurzfassung

The aerospace industry demands more efficient alternatives to conventional jet engines. In case of fuel con- sumption, modern turbo-prop engines have been identified as an efficient alternative for short range aircraft. However, the benefit in operation efficiency may come along with a strong acoustic excitation on the fuselage. In order to continue improving the aircraft cabin acoustic comfort achieved with turbofan powered aircraft, additional countermeasures are necessary. Therefore, a better understanding of the dynamic behaviour of the fuselage is essential for the development of new and commercially successful noise-reducing measures. For acoustic purposes, the relevant frequency range of the tonal excitations of the turbo-prop engines is the so called mid-frequency range. Numerical structural-dynamical models used for vibroacoustic predictions and analyses often show significant deviations from experimental results in the mid-frequency range. A model validation based on the correlation with experimentally determined modal parameters is often not possible due to the high modal density that aircraft fuselages exhibit in this frequency range. The correlation criterion introduced in this work is based on kinetic energies integrated over frequency bands and spatially over surface areas of the fuselage. The objective is to identify frequency bands where the numerical model needs to be adjusted for a better match with experimental observations even in a frequency range of high modal density and overlap.