Shape Optimization and Sensitivity Analysis of a Liner under Grazing Flow

在许多技术应用中，声学衬垫作为消声器发挥着关键作用。该项目的目的是为了更好地了解控制降噪的机制。我们将密切监测声场与线型湍流之间的耦合。首先，我们要最大限度地减少各种衬垫的声音衰减，每个衬垫在不同的频率上工作。为此，我们计划应用最优形状设计（OSD）工具。精确地说，将使用伴随Navier-Stokes方程的梯度法。基于这种形状优化，我们想比较不同优化运行的流场和声场。特别是，特征流体结构及其各自频率/衰减的变化应使用动态模态分解（DMD）进行分析。这些优化特定频率后dmd模态/特征值的变化表明了相关的阻尼机理。此外，为了确定衰减的灵敏度，应进行从dmd模式改编的近似灵敏度分析。在我们的初步工作中，DMD和OSD工具已经可以成功应用。在Liner的情况下，这样的方法是新的。

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.