Parametric approach to primary structure modeling of aircraft for cabin noise analysis in FEM

The goals of the European Green Deal require the development of low-emission aircraft propulsion systems that consider sustainable fuels. However, there is a conflict of objectives between effective fuel reduction and noise development of the propulsion system, as particularly efficient propulsion concepts are often based on open rotors, which usually cause increased exterior and interior noise. As a result, precise vibroacoustic models are essential in the early design phase to evaluate and mitigate cabin noise. However, many essential details required for accurate cabin noise prediction are not yet fully defined during preliminary aircraft design. Consequently, the simulation chain consisting of the excitation, primary structure, secondary structure and cavity contains numerous assumptions. To address this challenge, this publication focuses on the parametric creation of full primary structure models based on preliminary design data, with a level of detail relevant for the vibroacoustic frequency range. A central contribution of this work is the derivation of generic modeling guidelines, such as wave-resolving element discretization in the circumferential direction and longitudinal direction of the fuselage structure as well as parameterization of rivet stiffness, from high-resolution experimental vibration data from the research platform Acoustic Flight-Lab. These guidelines are applicable to other fuselage configurations and aim to improve the accuracy of automated FE models. In addition to model creation, this publication proposes an approach for early vibroacoustic assessment at the primary structure level, utilizing spatially and spectrally integrated energy distributions. The applicability of this approach is demonstrated on two different aircraft configurations using realistic operating excitations of V2500 engines in cruise flight.