Vortex dynamics and energy transfer in turbulent 3D bluff-body wakes.

钝体是对工业和环境重要的各种流动几何形状的诊断简化，例如：独立式结构(建筑物、桥梁、风力涡轮机)；混合设备(燃烧室、化学反应器或热交换器)；崎岖和城市地形。障碍物表面的流动分离过程产生了高能量、大范围的旋转和循环流动区域。这些相干的流动结构相互作用，导致速度场扭曲，导致能量转移到较小但更强烈的运动，这些运动向下游传播，导致高水平的集中速度波动(湍流)、不稳定的力和增强的混合。本程序解决了理解这些流动和设计设备的基本和应用挑战：开发稳健的和统计上客观的技术来表征非恒定流行为，建立模拟和控制这些流动的数学框架；以及基本了解几何和入射流动条件如何影响流动物理。 五年的研究目标是了解和控制表面安装钝体的湍流尾迹动力学，重点研究入射边界层、障碍物几何形状和尖端流动相互作用对湍流特性和流动演变的影响。这项工作的基础是广义诊断条件平均技术的发展，以客观地表示连贯和湍流运动。这种方法为建立动态一致的降阶数学模型以研究能量传递和流量控制策略奠定了基础。 该计划的成果是与基础研究和实践相关的重要科学和工程进展。这项研究涉及预测和控制。拟议的实验是启发式简化，旨在提供与流动-装置、流体-结构相互作用、混合过程和环境安全相关的尾流基本物理方面的见解。广义条件平均方法通过分离确定性(相干)和随机(湍流)能量贡献，允许新的、动态一致的方法来分析非恒定流行为。例如，由此得到的表示法提高了非定常负荷预测的准确性，并产生了指导湍流模型开发的新见解。这种方法可以推广到结构动力学和噪声产生的研究中。降阶公式是流量控制策略的基石，例如抑制压缩机或风力涡轮机叶片上的噪音产生或失速。这项技术可以通过提供快速交互可视化工具来改进设计实践，该工具能够隔离和模拟工程相关的流量，而无需求助于广泛且耗时的模拟程序。 在这个项目中，高素质的人员接受最先进的光学技术、遥感技术、数学和计算工具方面的培训。重点是在流体力学基础及其在工业驱动的工程开发中的应用方面发展强大的专业知识。培训的跨学科性质得到了国际和国家合作的补充。这一战略旨在培养独立工程师，具有健全的批判性判断和灵活的技能。 该计划对加拿大的潜在好处是：提高行业竞争力和降低温室气体排放(例如，改进的飞机发动机和风力涡轮机性能)；减轻风灾；新技术和对高素质人员的高级培训。

Bluff-bodies are diagnostic simplifications for a wide range of flow geometries of industrial and environmental importance such as: free-standing structures (buildings, bridges, wind turbines); mixing devices (in combustors, chemical reactors or heat exchangers); rough and urban terrain. The flow separation process on the obstacle surfaces gives rise to highly energetic, large-scale regions of rotating and recirculating flow. These coherent flow structures interact, causing distortions of the velocity field leading to energy transfer to smaller but more intense motions, which travel downstream and are responsible for high levels of concentrated velocity fluctuations (turbulence), unsteady forces and enhanced mixing. The present program addresses fundamental and applied challenges for understanding these flows and designing devices: the development of robust and statistically objective techniques to characterize unsteady flow behaviour, the formulation of a mathematical framework for modelling and controlling these flows; and a fundamental understanding of how geometry and incident flow conditions affect the flow physics. The five-year research objectives are to understand and control the dynamics of turbulent wakes for surface-mounted bluff-bodies; focusing on the influence of the incident boundary layer, obstacle geometry and tip-flow interactions on turbulence characteristics and flow evolution. This work is underpinned by the development of generalized diagnostic conditional averaging techniques to objectively represent coherent and turbulent motion. This approach sets the basis for dynamically consistent reduced-order mathematical models to investigate energy transfer and flow control strategies. The outcomes of this program are important scientific and engineering advances relevant to fundamental studies and practice. The research addresses prediction and control. The proposed experiments are heuristic simplifications designed to provide insights in the underlying physics of wake flows pertinent to flow-devices, fluid-structure interactions, mixing processes and environmental safety. The generalized conditional averaging methodology permits novel, dynamically consistent approaches for analysing unsteady flow behaviour by separating deterministic (coherent) and stochastic (turbulent) energetic contributions. The resulting representation, for example, improves the accuracy of unsteady-load predictions and yields new insights to guide turbulence model development. This approach can be extended to studies of structural dynamics and noise generation. The reduced-order formulation is a cornerstone of flow control strategies, e.g. to suppress noise generation or stall on compressor or wind turbine blades. This technique can improve design practice by providing a rapid interactive visualisation tool, capable of isolating and modelling engineering relevant flow quantities, without recourse to extensive and time-consuming simulation procedures. In this program highly qualified personnel are trained in state-of-the-art optical techniques, remote-sensing technologies, mathematical and computational tools. The focus is to develop a strong expertise in fluid mechanics fundamentals and their applications to industry driven engineering developments. The interdisciplinary nature of the training is supplemented by international and national collaborations. This strategy aims to develop independent engineers, with sound critical judgment and flexible skills. The program’s potential benefits to Canada are: increased industry competitiveness and lower greenhouse gas emissions (e.g. improved aircraft engine and wind turbine performance); wind-damage mitigation; new technologies and advanced training of highly qualified personnel.