Risk Assessment Method for Encounters with Perturbed Wake Vortices

除少数例外情况外，飞机尾涡遭遇的风险分析和严重性评估均采用了两个反向旋转直涡的简化模型。实际上，老化的涡旋会产生波浪形变形，根据大气条件，这种变形会导致涡旋环破裂。到目前为止，这种影响的后果通常被忽视。然而，为了评估降低的最小间隔要求和更有效地利用空气空间的新概念，必须考虑影响尾随飞机潜在尾涡危险的所有机制。本项目的目的是研究尾流涡流变形对遭遇飞机的潜在危险的影响，并开发一种方法，通过该方法可以在尾流紊流相关的安全分析中考虑变形。中心假设是尾流变形降低了尾流涡流的风险，并可能有助于修正目前在许多条件下被认为是保守的分离最小值。因此，该项目的活动有助于实现当前的研究目标，为主要机场日益增长的容量问题提供解决方案。利用尾流衰减的大涡模拟（LES）得到的三维速度场，建立了变形涡的真实的和快速的模拟模型。它们目前为尾涡遭遇模拟提供了最高的建模保真度。它们被用于飞行模拟器，以研究尾流变形对飞行员评估遭遇严重程度的影响，以及着陆进场过程中尾流遭遇的初始蒙特-卡罗模拟（MCS）。结果表明，轴向相遇位置必须被认为是一个额外的参数来评估尾流变形的影响。项目延期的目的是通过对所述假设的评估来完成这些活动。目前的结果表明，尾流变形的简化分析模型很好地代表。关于涡强度随涡龄增加的适应性仍需研究，因为最先进的尾涡模型仅涵盖“全球”环流，而此处需要“局部”环流。用高保真LES速度场模拟的相遇被用作验证涡流模拟模型的参考。分析的核心是具有相当高的样本量的MCS，用于回答中心问题：变形尾涡比直涡危险性小吗？

With a few exceptions, risk analyses and severity assessments of aircraft wake vortex encounters have applied the simplified model of two counter-rotating straight vortices. In reality, aging vortices develop a wavy deformation that can lead to a breakup into vortex rings depending on the atmospheric conditions. Up to now, the consequences of this effect were usually neglected. However, in order to assess reduced minimum separation requirements and new concepts for a more efficient use of airspace, all mechanisms affecting the potential wake vortex hazard of trailing aircraft have to be regarded. The objective of this project is to investigate the impact of wake vortex deformation on the potential hazard for an encountering aircraft and to develop a methodology by which the deformation can be considered in wake turbulence related safety analyses. The central hypothesis is that wake deformation reduces the wake vortex risk and may contribute to a revision of today's separation minima that are considered conservative under many conditions. Thus, the activities of this project contribute to current research objectives to provide solutions for the growing capacity problem at major airports.Several important milestones were achieved during the previous project phase. Using 3D velocity fields, which were derived from large-eddy simulations (LES) of wake decay, real- and fast-time simulation models of deformed vortices were developed. They currently offer the highest modelling fidelity for wake vortex encounter simulations. They were used in flight simulators to investigate the impact of wake deformation on pilot's assessment of encounter severity as well as for initial Monte-Carlo Simulations (MCS) of wake encounters during landing approach. The results show that the axial encounter location has to be considered as an additional parameter to assess the impact of wake deformations. The project extension aims to finalize these activities with an assessment of the stated hypotheses. Current results show, that the wake deformation is well represented by the simplified analytical models. Research is still needed regarding the adaption of the vortex strength with increasing vortex age, as state-of-the-art wake vortex models only cover a 'global' circulation, whereas the 'local' circulation is required here. Encounters simulated with the high-fidelity LES velocity fields are used as reference for the validation of the vortex simulation models. The core of the analysis are MCS with considerably higher sample sizes that serve to answer the central question: Are deformed wake vortices less hazardous than straight vortices?