The present study is related to the numerical prediction of propulsive noise emissions by aircraft. More precisely this study addresses the modeling of "sound absorbing materials" (or "acoustic liners"), in the context of time-domain CAA (Computational AeroAcoustics) methods. Such modeling raises several key questions, which are related to various aspects such as the type of flow involved (heterogeneities, turbulent boundary layers, etc.), the sound levels considered (non-linear phenomena), the diffraction effects induced by ruptures of impedance, etc. As a first step, the present study consists in validating and improving the time-domain impedance boundary condition implemented in Onera's structured CAA solver (named sAbrinA.v0). Theoretical developments are first devoted to the modeling of impedance in the time-domain, and lead to a discussion on the uniqueness of the solution found for a given material. The work consists in CAA-simulating several canonical tests of noise absorption by acoustic liners. Outputs are then compared against experimental and/or analytical results, delivering new insight in the way noise absorption materials can be accurately modeled and simulated using time-domain CAA-approaches.
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