An Integrated Framework for High-Order Aeroacoustics of Complex Configurations

由于分辨率的要求，直接数值模拟噪声的产生和传播对于工程问题来说仍然是非常昂贵的。因此，采用混合方法，即通过适当的计算流体动力学模拟来预测近场流量，通过气动声学积分方法或声学类比公式来预测远场声辐射。计算流体动力学模拟准确地捕捉与近场声音产生相关的复杂流动物理是至关重要的。因此，有必要使用具有极低色散/耗散误差的高阶数值格式。此外，最重要的机身噪声源是起落架和高升力部件，如板条和襟翼。这些组件的几何复杂性要求使用能够在非结构化网格上表现良好的数值方法。高阶Vincent-Castonguay-Jameson-Huynh （VCJH）计划最近由斯坦福大学的首席研究员和同事在国家科学基金会的资助下开发，满足了上述两个要求。在目前的工作中，将开发一个最先进的计算框架，通过集成用于湍流大涡模拟（LES）的先进子网格尺度（SGS）模型，以及用于声音传播的新的Ffowcs williams - hawkins （FWH）声学类比公式，以及用于非结构化网格的支持图形处理单元（GPU）的高阶VCJH流动求解器，来进行气动声学模拟。由此产生的软件将使首席研究员和同事能够以可承受的成本在复杂的配置上进行高保真的大规模空气声学模拟。进行这种模拟的能力将极大地促进设计具有低噪声特征的新飞机。商业航空运输的未来增长（目前预计到2030年将增长两倍）可能会受到其不利环境影响（排放和噪音）的严重限制。噪音法规已经并将继续变得越来越严格，减少噪音现在是运输飞机设计的一个主要考虑因素。尽管计算机模拟目前在飞机设计中发挥着重要作用，但它们预测噪音，特别是机身噪音（着陆时噪音的最大组成部分）的能力仍然非常有限。首席研究员和他的同事们的目标是结合新的数学和计算技术来推进最先进的噪音预测，从而设计出新的、更安静的飞机，最终目标是将它们的噪音足迹限制在机场范围内。一个成功的结果对美国经济意义重大，因为商用飞机仍然是最大的单一出口部门。

Direct numerical simulation of noise production and propagation remains prohibitively expensive for engineering problems due to resolution requirements. Consequently, hybrid approaches are adopted, which consist of predicting near-field flow quantities via a suitable computational fluid dynamics simulation, and far-field sound radiation by aero-acoustic integral methods, or acoustic analogy formulations. It is critical that the complex flow physics associated with sound generation in the near field is accurately captured by the computational fluid dynamics simulation. Therefore, it is necessary to use a high-order numerical scheme with very low dispersion/dissipation errors. Also, the most significant airframe noise sources are landing gear and high-lift components, such as slats and flaps. The geometric complexity of these components calls for use of numerical methods that can perform well on unstructured grids. The high-order Vincent-Castonguay-Jameson-Huynh (VCJH) schemes recently developed by the principal investigator and colleagues at Stanford University with National Science Foundation funding satisfy both of the aforementioned requirements. In the present work, a state-of-the-art computational framework will be developed for performing aero-acoustics simulations by integrating advanced sub-grid scale (SGS) models for large-eddy simulations (LES) of turbulent flow, and a new Ffowcs Williams-Hawkings (FWH) acoustic analogy formulation for sound propagation, with a graphical processing unit (GPU) enabled high-order VCJH flow solver for unstructured grids. The resulting software will enable the principal investigator and colleagues to undertake high-fidelity large scale aero-acoustics simulations over complex configurations at an affordable cost. The ability to perform such simulations will greatly facilitate design of new aircraft with reduced noise signatures.The future growth of commercial air transportation (currently predicted to triple by the year 2030) may be severely limited by its adverse environmental impacts (both emissions and noise). Noise regulations have become, and will continue to become, increasingly stringent, and noise reduction is now a major consideration in the design of transport aircraft. Although computer simulations currently play a major role in airplane design, their ability to predict noise, and in particular airframe noise (which is the largest component of noise during landing) remains very limited. The principal investigator and his colleagues aim to combine new mathematical and computational techniques to advance the state-of-the-art in noise prediction, and thereby enable design of new, quieter aircraft, with the ultimate target of restricting their noise footprint to within airport perimeters. A successful outcome is significant to the United States economy because commercial aircraft continue to be the largest single export sector.