Scale Interactions in Wall Turbulence: Old Challenges Tackled with New Perspectives

壁湍流中的尺度相互作用：用新视角应对旧挑战

• 批准号: EP/I037938/1
• 负责人: Jonathan Morrison
• 金额: $ 52.58万
• 依托单位: Imperial College London
• 依托单位国家: 英国
• 项目类别: Research Grant
• 财政年份: 2012
• 资助国家: 英国
• 起止时间: 2012 至 无数据
• 项目状态: 已结题
• 来源: https://gtr.ukri.org/projects?ref=EP%2FI037938%2F1
• 关键词: Scale; Interactions; Wall; Turbulence; Old

The need to improve the efficiency of fluid-based systems is now of paramount importance. In experimental aerodynamics, one of the most difficult measurements is an accurate determination of surface friction. Our need to predict it accurately is fundamentally important to the design of efficient systems. Reynolds number similarity is an essential concept in describing the fundamental properties of turbulent wall-bounded flow. Unlike the drag coefficient for bluff bodies, that for a turbulent boundary layer continues to decrease indefinitely with increasing Reynolds number because the small-scale motion near the surface is directly affected by viscosity at any Reynolds number. Therefore Reynolds number similarity is very important in design and is a vital tool for the engineer, who, plied with information from either direct numerical simulations or wind-tunnel tests (or both), may well have to extrapolate over several orders of magnitude in order to estimate quantities such as drag at engineering or even meteorological Reynolds numbers. Perhaps the most well-known example of Reynolds number similarity is the region of log velocity variation (the log law) found in wall-bounded flows which, at sufficiently high Reynolds numbers, exists regardless of the nature of the surface boundary condition or the form of the outer imposed length scale.In wall-bounded flows relevant to practical applications, where the flow is turbulent and the Reynolds number is high, the transport and loss of fluid momentum and energy is not well understood. Consequently, most predictive and modelling methods rely on a variety of assumptions. The two most critical ones are the Law of the Wall (the log law) and Townsend's local-equilibrium hypothesis. Both assumptions implicitly assume that large scales in the flow are weak and that they function independently of the small scales. However, this is clearly not true, especially in flows of engineering importance, such as when the surface is rough or when the flow is not in equilibrium. In fact, there is a multiscale interaction, referred to here as an inner-outer interaction (IOI), where the large scales influence the dynamics of the small scales and vice-versa. These interactions are not well understood and therefore any corrections to the predictive models to include these interactions are essentially achieved through ad-hoc means.A better understanding of IOI will help explain the apparent non-universality of the constants in the log law and will certainly influence the development of models for both Reynolds-Averaged Navier-Stokes (RANS) calculation methods, Large-Eddy Simulations (LES) and hybrid RANS-LES. It will also be useful in the development of models for the control of wall turbulence, complementing knowledge from Direct Numerical Simulations which, we believe, are inherently incomplete owing to the restriction to low Reynolds numbers. Accurate models for prediction and control at realistic Reynolds numbers typical of practical applications will have to address IOI. Researchers working in specific areas of internal rough-wall flows, rough-wall boundary layers and freestream turbulence effects on boundary layers will also benefit from this fundamental work. All these aspects are abundantly present in a variety of practical applications and natural systems. For example, researchers exploring modelling strategies for practical applications such as oil and natural-gas pipelines, ship hulls and the natural and urban terrains will find the the data obtained from the roughness experiments to be very useful for validation exercises. Similarly, researchers in the area of turbomachinery will find the data from the roughness and freestream turbulence experiments extremely useful.

现在，提高基于流体的系统的效率的需求现在至关重要。在实验空气动力学中，最困难的测量之一是对表面摩擦的准确确定。我们需要准确预测它对于高效系统的设计至关重要。 Reynolds数字相似性是描述湍流结合流动流的基本特性的重要概念。与虚张声板的阻力系数不同，对于湍流边界层而言，随着雷诺数的增加，湍流边界层继续无限期减少，因为在任何雷诺数下，表面附近的小规模运动都受到粘度的直接影响。因此，雷诺数在设计中非常重要，对于工程师来说是重要的工具，他们在直接数值模拟或风孔测试（或两者兼而有之）很可能必须在几个数量级上推断以估算工程范围等数量的数量，例如在工程上的阻力，甚至是我们气息的Reynolds数量。雷诺数数字相似性的最著名例子也许是壁速变化的区域（log定律）在壁挂式流动中发现的区域，在足够高的雷诺数数字上，无论表面边界条件的性质或外部强加的长度尺度与壁式的流量相关，而在较高的壁范围内，其流量及其损失的损失与流动的数量相关。能量不太了解。因此，大多数预测性和建模方法都依赖于各种假设。最关键的两个是墙的定律（原木法）和汤森的局部平衡假设。这两个假设都隐含地假设流动中的较大尺度是弱的，并且它们独立于小尺度。但是，这显然不是正确的，尤其是在工程重要性的流动中，例如表面粗糙或流动不平衡时。实际上，这里有一种多尺度相互作用，在这里称为内在交互（IOI），其中大尺度会影响小尺度和反之亦然的动力学。这些相互作用的理解尚不很好，因此对预测模型的任何更正都可以通过临时手段来实现这些相互作用。对IOI的更好理解将有助于解释日志定律中常数的明显非大学性，并且一定会影响两种雷诺•雷诺（Reynolds-average）的纳维尔·斯托克斯（Navier-Stokes）（rans）carverans carters cacters and simers and and and and and ressedy and ressed and ressed and ressed and ressed and ressecty（lidse）。它在开发壁湍流模型的开发中也将很有用，并补充了直接数值模拟的知识，我们认为，由于限制了较低的雷诺数，我们认为这是本质上不完整的。在现实的雷诺数字上进行预测和控制的准确模型将必须解决IOI。在内部粗壁流，粗壁边界层和自由式湍流对边界层的特定领域工作的研究人员也将受益于这项基本工作。所有这些方面都大量存在于各种实际应用和自然系统中。例如，研究人员探索针对石油和天然气管道，船体以及自然和城市地形等实用应用的建模策略，将发现从粗糙度实验获得的数据对于验证练习非常有用。同样，涡轮机械领域的研究人员将从粗糙度和自由度湍流实验中找到数据非常有用。

项目成果

Denoising of time-resolved PIV for accurate measurement of turbulence spectra and reduced error in derivatives

对时间分辨 PIV 进行去噪，以精确测量湍流谱并减少导数误差

• DOI: 10.1007/s00348-012-1375-4
• 发表时间: 2012
• 期刊: Experiments in Fluids
• 影响因子: 2.4
• 作者: Oxlade A

Adaptive Kagome Lattices for Near Wall Turbulence Suppression

用于近壁湍流抑制的自适应 Kagome 晶格

• DOI: 10.2514/6.2015-0270
• 发表时间: 2015
• 作者: Bird J

Intermediate scaling and logarithmic invariance in turbulent pipe flow

湍流管流中的中间标度和对数不变性

• DOI: 10.1017/jfm.2021.71
• 发表时间: 2021
• 期刊: Journal of Fluid Mechanics
• 影响因子: 3.7
• 作者: Diwan S

Reynolds-number dependence of the Townsend-Perry 'constant' in wall turbulence

壁湍流中汤森-佩里“常数”的雷诺数依赖性

• 发表时间: 2019
• 期刊: 11th International Symposium on Turbulence and Shear Flow Phenomena, TSFP 2019
• 作者: Diwan S.S.

Experimental Control of Turbulent Boundary Layers with In-plane Travelling Waves.

• DOI: 10.1007/s10494-018-9926-2
• 发表时间: 2018
• 期刊: Flow, turbulence and combustion
• 作者: Bird J;Santer M;Morrison JF
• 通讯作者: Morrison JF