Advanced Instability Methods (AIM) Network

高级不稳定性方法 (AIM) 网络

• 批准号: EP/G033803/1
• 负责人: Matthew Juniper
• 金额: $ 10.27万
• 依托单位: University of Cambridge
• 依托单位国家: 英国
• 项目类别: Research Grant
• 财政年份: 2009
• 资助国家: 英国
• 起止时间: 2009 至 无数据
• 项目状态: 已结题
• 来源: https://gtr.ukri.org/projects?ref=EP%2FG033803%2F1
• 关键词: Advanced; Instability; Methods; AIM; Network

In many scientific and industrial situations, it is important to predict whether a small perturbation in a flow will grow (unstable flow) or decay (stable flow). Industrial applications of stability theory include: the break-up of the jet in an ink-jet printer; large scale mixing in a combustion chamber; thermo-acoustic oscillation in a gas turbine; coupled mode flutter of a wind turbine and mixing in small channels for pharmaceutical applications. The conventional technique is to decompose the perturbation into modes that are normal (i.e. orthogonal) in two spatial dimensions and to study the growth of each mode separately. This, however, often gives inaccurate results. As a simple example, this technique predicts that the flow in a pipe will be stable at all Reynolds (Re) numbers (i.e. at all velocities). In reality, however, the flow becomes turbulent at Re ~ 2000, depending on external noise and the pipe's roughness.This discrepancy arises because, in the third spatial dimension, the modes are non-normal (i.e. non-orthogonal). This means that they can feed energy into each other and should not be considered separately. This non-normal behaviour often causes strong transient growth at the intermediate times that are of most interest to scientists and engineers. For instance, in pipe flow, a non-normal analysis predicts that tiny perturbations will rapidly develop into stream-wise streaks at Re ~ 2000, agreeing with experimental evidence. In the last decade, there has been a surge of interest in non-normal stability analysis within the applied maths community. It is widely thought that non-normality is the root cause of the transient behaviour of the simple flows they have analysed. The aim of this network is to accelerate its exploitation in more complex flows, particularly those with industrial relevance. Conventional stability analyses are currently applied to many industrial situations and, as for simple flows, could miss some of the most significant behaviour.Non-normal analyses, as well as being more accurate, also predict the regions of a flow that are most influential in creating a desired result, such as good mixing. With development, this information will allow engineers to design 'backwards' from an end result, rather than 'forwards' by trial and error. Our long term vision is that the next generation of Computational Fluid Dynamics tools will contain modules that can perform non-normal stability analysis. An important goal is to distinguish between the situations in which a non-normal analysis is required and those in which a conventional analysis is sufficient. We will do this both by reviewing the canonical flows, such as jets/wakes, pipe flow, boundary layers and thermo-acoustic oscillations in a Rijke tube, and by accelerating work on a number of industrial case studies.To achieve this, we will create a multi-disciplinary international network with both academic and industrial partners. The technical goals will require a broad range of expertise: mathematical, to retain the understanding developed for the canonical flows; numerical, to perform the high order computations that will be necessary when moving from simple to complicated flows; experimental, to assemble a catalogue of evidence that will demonstrate when the technique is more relevant than normal mode analysis. The network will expand to a broader industrial community as the ranges of applicability becomes clearer. Currently, several groups are working in this area but, in this relatively young field, there is little formal interaction between them. The network will build on the UK's traditional strength in flow instability and incorporate partners from India, where there has recently been some outstanding work in non-normal analysis. The network will start with one very significant overseas partner (Peter Schmid from Ecole Polytechnique, France) and expand internationally during the two year start-up period.

在许多科学和工业情况下，重要的是预测流动中的小扰动是否会增长（不稳定流动）或衰减（稳定流动）。稳定性理论的工业应用包括：喷墨打印机中射流的分裂;燃烧室中的大规模混合;燃气涡轮机中的热声振荡;风力涡轮机的耦合模式颤振和制药应用中的小通道中的混合。传统的技术是将扰动分解成在两个空间维度上正常（即正交）的模式，并分别研究每个模式的增长。然而，这往往给出不准确的结果。作为一个简单的例子，该技术预测管道中的流动在所有雷诺数（Re）下（即在所有速度下）都是稳定的。然而，实际上，根据外部噪声和管道粗糙度的不同，雷诺数约为2000时，流动会变成湍流。这种差异的产生是因为在第三空间维度上，模式是非正交的。这意味着它们可以相互提供能量，不应单独考虑。这种非正常的行为往往会在科学家和工程师最感兴趣的中间时间引起强烈的瞬时增长。例如，在管流中，非正态分析预测，微小扰动将在Re ~ 2000时迅速发展成流向条纹，这与实验证据一致。在过去的十年中，应用数学界对非正态稳定性分析的兴趣激增。人们普遍认为，非正态性是他们所分析的简单流动的瞬态行为的根本原因。该网络的目的是加速其在更复杂的流程中的开发，特别是那些与工业相关的流程。传统的稳定性分析目前应用于许多工业场合，对于简单的流动，可能会错过一些最重要的行为。非正态分析不仅更准确，而且还能预测对产生理想结果（如良好混合）最有影响的流动区域。随着开发，这些信息将允许工程师从最终结果“向后”设计，而不是通过试错“向前”设计。我们的长期愿景是，下一代计算流体动力学工具将包含可以执行非正常稳定性分析的模块。一个重要的目标是区分需要非正态分析的情况和常规分析就足够的情况。我们将通过回顾规范流（如射流/尾流、管流、边界层和Rijke管中的热声振荡）以及加快大量工业案例研究的工作来实现这一目标。为此，我们将与学术界和工业界合作伙伴建立一个多学科的国际网络。技术目标将需要广泛的专业知识：数学，以保持对规范流的理解;数值，执行从简单流到复杂流时所需的高阶计算;实验，收集证据目录，证明该技术何时比正常模式分析更相关。随着适用范围变得更加清晰，该网络将扩展到更广泛的工业社区。目前，有几个团体正在这一领域开展工作，但在这个相对年轻的领域，它们之间几乎没有正式的互动。该网络将建立在英国在流动不稳定性方面的传统优势基础上，并将印度的合作伙伴纳入其中，印度最近在非正常分析方面有一些出色的工作。该网络将从一个非常重要的海外合作伙伴（法国Ecole Polytechnique的Peter Schmid）开始，并在两年的启动期内向国际扩展。

项目成果

Modal Stability Theory

模态稳定性理论

• DOI: 10.1115/1.4026604
• 发表时间: 2014
• 期刊: Applied Mechanics Reviews
• 影响因子: 14.3
• 作者: Juniper M

Triggering in the horizontal Rijke tube: non-normality, transient growth and bypass transition

• DOI: 10.1017/s0022112010004453
• 发表时间: 2011-01-25
• 期刊: JOURNAL OF FLUID MECHANICS
• 影响因子: 3.7
• 作者: Juniper, Matthew P.

The two classes of primary modal instability in laminar separation bubbles

层流分离气泡中的两类主模态不稳定性

• DOI: 10.1017/jfm.2013.504
• 发表时间: 2013
• 期刊: Journal of Fluid Mechanics
• 影响因子: 3.7
• 作者: Rodríguez D

Non-normality in combustion-acoustic interaction in diffusion flames: a critical revision

扩散火焰中燃烧声相互作用的非正态性：重要修订

• DOI: 10.1017/jfm.2013.468
• 发表时间: 2013
• 期刊: Journal of Fluid Mechanics
• 影响因子: 3.7
• 作者: Magri L

Triggering, bypass transition and the effect of noise on a linearly stable thermoacoustic system

触发、旁路转换和噪声对线性稳定热声系统的影响

• DOI: 10.1016/j.proci.2010.06.018
• 发表时间: 2011
• 期刊: Proceedings of the Combustion Institute
• 影响因子: 3.4
• 作者: Waugh I