Numerical simulation of jet mixing noise associated with engine exhausts

本课题是关于发动机排气噪声的数值预测。这一主题是特别感兴趣的，因为它涉及到许多不同的流动特征，冷，热射流湍流，自由剪切层和壁面有界流动的混合。因此，为了获得亚音速射流中声源及其近场的精确估计，必须在计算流体动力学代码中实现特殊的数值开发。将与项目的其他CFD合作伙伴一起研究和验证几种数值方法。与此同时，将讨论关于非定常壁流计算的物理相关性及其对声学远场估计的适用性的困难问题。为此目的，将使用法国伙伴的一个试验性基准。该基准结合了湍流射流与圆柱冲击下游翼型的准周期扰动。因此，在湍流射流附近的壁边界流动的问题是实验解决。这项实验的大部分结果已经公布，但还将进行一些额外的测量。将在非定常流场和声学远场上进行比较。远场计算将通过将瞬时源项集成到Ffwocs-Williams-Hawkings类比的高级时间公式中来实现。

This project is concerned with the numerical prediction of engine exhaust noise. This topic is of particular interest because it involves many different flow features, mixing of cold and hot jet turbulent flows, free shear layers and wall bounded flows. Therefore, special numerical developments will have to be achieved in the CFD codes in order to obtain accurate estimates of the acoustic sources and their near field in subsonic jets. Several numerical approaches will be investigated and validated with other CFD partners of the project. In parallel the difficult question about the physical relevance of unsteady wall flow computations and their applicability to acoustic far field estimates will be addressed. For that purpose, an experimental benchmark from the French partner will be used. This benchmark combines a turbulent jet flow with the quasi periodic disturbance of a circular cylinder impinging on a downstream located airfoil. Thus, the problem of a wall bounded flow in the vicinity of a turbulent jet flow is addressed experimentally. Most results of this experiment are already available, but a few additional measurements will be carried out. Comparisons will be made both on the unsteady flow field and on the acoustic far field. Far field computations will be achieved by integrating the instantaneous sources terms into an advanced time formulation of the Ffwocs-Williams-Hawkings analogy.