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

崖体是对工业和环境重要性的各种流动几何形状的诊断简化，例如：独立结构（建筑物，桥梁，风力涡轮机）；混合装置（燃烧器、化学反应器或热交换器）；崎岖不平的城市地形。障碍物表面的流动分离过程产生了高能量、大范围的旋转和再循环流动区域。这些连贯的流动结构相互作用，造成速度场的扭曲，导致能量转移到更小但更激烈的运动中，这些运动向下游传播，并导致高度集中的速度波动（湍流）、非定常力和增强的混合。目前的计划解决了理解这些流动和设计设备的基本和应用挑战：开发稳健和统计客观的技术来表征非定常流动行为，制定数学框架来建模和控制这些流动；以及对几何和入射流条件如何影响流物理的基本理解。

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.