Barbarino, Mattia (2013) Aeroacoustic methods for low-noise technologies design. [Tesi di dottorato]

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As environmental concerns are gaining increased public attention and with the rapid growth of air traffic foreseen in the forthcoming years, the scientific community and aircraft manufacturers are devoting significant resources in developing fast and reliable methods to deliver low noise design solutions. Since fully-resolved Navier–Stokes equations (DNS), and even filtered Navier-Stokes equations such as LES and DES methods, are still too computationally demanding for real applications, the present dissertation is focused on the theoretical and numerical formulation of different alternative computational aeroacoustic methods and their application to typical aeronautics low noise design problems. Following an introduction about the theoretical formulation of the Acoustic Analogy approach based on the Lighthill’s equation, the thesis is focused on the development of a Boundary Element Method (BEM) based on the convective wave equation for uniform mean flow. The BEM code kernel, developed for managing hybrid unstructured grids, builds up the global system matrix by assembling different matrix blocks for the governing equations and the boundary conditions. This strategy allows a more general and efficient implementation of the boundary conditions. The BEM code is also validated against classical analytical test cases for both internal and external problems. Moreover, the broadband noise generated by aircraft surfaces (Airframe noise) is presented with particular attention devoted to the development of RANS-based models for source field characterization. Finally the application of the developed methods to the analysis of the Landing Gear low-noise design problem is presented.

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