Prediction of Turbulent Flow-Induced Noise in Aircraft Cabins

Abstract

Flow-induced noise in aircraft cabins can be predicted through analytical models or numerical methods. However, the analytical methods existent nowadays were obtained for simple structures and cabins, in which, usually, a single panel is excited by the turbulent flow, and coupled with an acoustic enclosure. This paper discusses the development of analytical models for the prediction of aircraft cabin noise induced by the external turbulent boundary layer (TBL). The coupled structural-acoustic analytical model is developed using the contribution of both structural and acoustic natural modes. While, in previous works, only the contribution of an individual panel to the cabin interior noise was considered, here, the simultaneous contribution of multiple flow-excited panels is also analyzed. The analytical models were developed for rectangular and cylindrical cabins. The mathematical models were successfully validated through the good agreement with several independent experimental studies. Analytical predictions are presented for the interior sound pressure level (SPL) at different locations inside the cabins. It is shown that identical panels located at different positions have dissimilar contributions to the cabin interior noise, showing that the position of the vibrating panel is an important variable for the accurate prediction of cabin interior noise. Additionally, the results show that the number of vibrating panels significantly affects the interior noise levels. It is shown that the average SPL, over the cabin volume, increases with the number of vibrating panels. The space-averaged SPL is usually accepted to provide the necessary information for the noise prediction. However, in some real life applications, the local sound pressure may be desirable. To overcome this point, the model is also able to predict local SPL values, at specific locations in the cabin, which are also affected by number of vibrating panels, and often differ from the average SPL values. The developed analytical model can be used to study a wide range of different systems involving a cabin coupled with vibrating panels, excited by the TBL. The properties of the external flow, acoustic cabin, and panels, as well as the number of vibrating panels, can be easily changed to represent different systems. These abilities of the model make it a solid basis for future investigations involving the implementation of noise reduction techniques and multidisciplinary design optimization analyzes.