Identification and modelling of coherent structures in trailing vortex break-up

尾涡破裂中相干结构的识别和建模

• 批准号: 46192-2009
• 负责人: Holloway, Gordon
• 金额: $ 1.53万
• 依托单位: University of New Brunswick
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2014
• 资助国家: 加拿大
• 起止时间: 2014-01-01 至 2015-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=544985
• 关键词: Identification; modelling; coherent; structures; trailing

Trailing vortices are an inherent feature of aircraft flight and are primarily responsible for the swirling air motions observed in an aircraft wake. They present an in-flight hazard to aircraft and therefore place constraints on flight paths and the timing of take-off and landings at airports. Trailing vortices also have a strong influence on the dispersion of jet engine exhaust pollutants and pesticides in aerial spray applications. There is a substantial ongoing research effort to predict and, if possible, control the development of trailing vortices. Generally the objective is to limit vortex longevity by exciting the inherent modes of instability that exist within them. There has been extensive theoretical study of these instabilities but relatively few attempts to directly test for their presence in the laboratory. In spite of this fact many devices have been proposed to limit vortex longevity and some have been moderately successful. One device that has demonstrated the ability to reduce the rate of swirl velocity and increase the rate of vortex diffusion is spanwise directed air jets mounted on the wing tips. The present research proposal is to conduct laboratory testing on a trailing vortex formed with tip jets and identify the modes of vortex instability excited and the subsequent coherent structures of vortex break-up that they produce. A comparison will then be made between the findings of this study and the existing theories of vortex instability with the expectation that the phenomenon can be better understood. In particular it may be possible to reduce the energy required to achieve vortex break-up if the disturbance is more precisely designed. The experimental methods used will include flow imaging and advanced pattern recognition techniques. Once identified attempts will also be made to model the effect of these "coherent structures" on vortex development. Ultimately an improved understanding of vortex dynamics will lead to more effective vortex control.

尾随涡流是飞机飞行的固有特征，是飞机尾流中观察到的旋转空气运动的主要原因。它们对飞机造成飞行中的危险，因此限制了飞行路线以及机场起飞和降落的时间。尾随涡流还对航空喷雾应用中喷气发动机废气污染物和农药的分散产生强烈影响。目前正在进行大量研究工作来预测并在可能的情况下控制尾随涡流的发展。一般来说，目标是通过激发涡旋内部存在的固有不稳定模式来限制涡旋寿命。人们对这些不稳定性进行了广泛的理论研究，但在实验室中直接测试它们的存在的尝试相对较少。尽管如此，人们还是提出了许多装置来限制涡流寿命，其中一些已经取得了一定的成功。一种已证明能够降低涡流速度并提高涡流扩散率的装置是安装在翼尖上的翼展方向定向空气喷射装置。目前的研究计划是对由尖端射流形成的尾涡进行实验室测试，并确定激发的涡流不稳定模式以及随后产生的涡流破裂的相干结构。然后将本研究的结果与现有的涡不稳定性理论进行比较，以期能够更好地理解这种现象。特别是，如果更精确地设计扰动，则可以减少实现涡流破碎所需的能量。使用的实验方法将包括流成像和先进的模式识别技术。一旦确定，还将尝试模拟这些“相干结构”对涡流发展的影响。最终，加深对涡流动力学的理解将带来更有效的涡流控制。