Exact coherent structures in shear flows

剪切流中的精确相干结构

• 批准号: 1943433
• 金额: --
• 依托单位: Imperial College London
• 依托单位国家: 英国
• 项目类别: Studentship
• 财政年份: 2017
• 资助国家: 英国
• 起止时间: 2017 至 无数据
• 项目状态: 已结题
• 来源: https://gtr.ukri.org/projects?ref=studentship-1943433
• 关键词: Exact; coherent; structures; shear; flows

The free-stream coherent structure theory developed by Deguchi & Hall (2014a), valid in the large Reynolds number asymptotic limit, will be extended to compressible flows and applied to jet flows. It was shown in the above paper that a nonlinear coherent structure can be supported at the edge of the jet, and the structure induces a much bigger streaky flow in the centre of the jet. In the presence of compressible effects the coherent structure can act as a source of acoustic radiation and might well be implicated in the high frequency 'screeching' tones of a compressible jet.In addition vortex-wave interactions capable of supporting other types of canonical exact coherent structures will be investigated in the compressible regime. Compressible shear flows are susceptible to inviscid instabilities when their incompressible counterparts are stable and so the likely vortex-wave interactions in a compressible flow will be quite different than the incompressible case.Both projects concern the development of sophisticated asymptotic procedures to reduce the full unsteady Navier Stokes equations to a simpler form where relatively simple numerical methods can be used to solve the reduced problem. The work will be applicable to a wide range of laminar and turbulent compressible shear flows.

Deguchi & Hall （2014a）提出的在大雷诺数渐近极限下有效的自由流相干结构理论将推广到可压缩流动，并应用于射流。结果表明，射流边缘可以支撑非线性相干结构，该结构在射流中心产生较大的条纹流。在存在可压缩效应的情况下，相干结构可以作为声辐射的来源，并且很可能与可压缩射流的高频“尖锐”音调有关。此外，涡波相互作用能够支持其他类型的规范精确相干结构将在可压缩状态下进行研究。当不可压缩剪切流稳定时，可压缩剪切流容易发生无粘失稳，因此在可压缩流动中可能出现的涡波相互作用将与不可压缩情况大不相同。这两个项目都涉及发展复杂的渐近过程，将完整的非定常Navier Stokes方程简化为更简单的形式，其中相对简单的数值方法可以用来解决简化的问题。这项工作将适用于广泛的层流和湍流可压缩剪切流。