Shape Optimization and Sensitivity Analysis of a Liner under Grazing Flow

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Acoustic Liners play a key role as silencers in many technical applications. The aim of the project is to gain a better understanding of the mechanism that governs the noise reduction. We will closely monitor the coupling between the sound field and the turbulent flow of a Liner.First we want to maximize the sound attenuation of various Liners, each working at a different frequency. For this purpose we plan to apply an Optimal Shape Design (OSD) tool. To be precise, a Gradient method with the adjoint Navier-Stokes equations will be used. Based on this shape optimization we would like to compare the flow field and the acoustic field of the various optimization runs. In particular, the modifications of the characteristic fluid structures and their respective frequencies / attenuations shall be analyzed with a Dynamic Mode Decomposition (DMD). These modifications of the DMD-modes /-eigenvalues after optimizing certain frequencies, indicate the related damping mechanism. Furthermore, an approximate Sensitivity analyses adapted from DMD-modes shall be carried out in order to determine the sensitivity of the attenuation.In our preliminary work the DMD as well as the OSD tool could already be applied successfully. In case of a Liner such methods are new.