Investigation of Asymmetric Free and Confined Three-dimensional Turbulent Jets using Time-Resolved Tomographic Particle Image Velocimetry

提出了一种新的数值和实验研究方案，用于研究自由射流和与固体壁面或自由表面相偏移的射流的混合和湍流特性。这些射流出现在许多工程应用中。这项研究的主要目标是提供对这些射流中湍流混合的科学理解，并创建一个高质量数据库存储库，使研究界能够开发出可靠的湍流射流预测工具。短期目标，将在未来5年内实现，是了解喷嘴几何形状的变化如何影响自由射流的湍流特性，并评估射流与刚性壁面或自由表面的偏移距离对湍流输运现象的影响。在这个5年的周期中，16名HQP（5名博士，1名硕士和10名学士）将接受培训，进行新颖的实验和数值模拟，使他们能够对湍流射流有一个全面的了解。他们将培养技能，为他们在学术界或对加拿大具有社会经济重要性的各种行业就业做好准备。射流将从圆形、矩形和椭圆形截面的喷嘴中产生，并将在与墙壁或自由表面的不同距离上偏移。世界一流的时间分辨层析粒子图像测速系统（TR-Tomo-PIV）将用于在三维域（c - 3d）对所有三个速度分量进行瞬时和同时测量，其量级在之前的湍流射流临近壁面或自由表面的实验研究中从未实现过。TR-Tomo-PIV是PIV的最新发展，PIV是一种革命性的湍流实验研究技术。3C-3D数据库将用于计算所有平均速度和高湍流统计，并对所提出的湍流射流进行适当的正交分解。将对衰减速率和扩散速率进行评估，以评估喷嘴几何形状的变化或与边界的偏移距离如何影响湍流射流的混合特性。***本方案中确定的射流比湍流模拟界模拟的典型剪切流更为复杂，并将代表数值模型的急性测试案例。实验结果还将有助于开发更有效的秒矩闭包，这些闭包往往没有经过全面现场测量的验证。这些新模型将使工程界减少对物理模型测试的依赖，并设计出高性能的流体系统。从这项研究和新的数值模型中获得的更好的理解将导致创新技术的发展，以及在航空航天、暖通空调和发电行业中节能环保工程系统的设计

A novel numerical and experimental research program is proposed to investigate the mixing and turbulence characteristics of free jets, and jets that are offset from a solid wall or free surface. These jets occur in many engineering applications. The main goal of the research is to provide scientific understanding of turbulence mixing in these jets and create a repository of high-quality databases that will enable the research community to develop reliable predictive tools for turbulent jets. The short-term objectives, which will be achieved over the next 5 years, are to understand how changes in nozzle geometry affects turbulence characteristics of free jets, and to evaluate the effects of offset distance of a jet from a rigid wall or free surface on turbulent transport phenomena. Over this 5-year cycle, 16 HQP (5 PhD, 1 MSc and 10 BSc) will be trained to perform novel experiments and numerical simulations that will enable them to develop a thorough understanding of turbulent jets. They will develop skills that will prepare them for employment in academia or diverse industries of socio-economic importance to Canada.***The jets will be produced from nozzles with round, rectangular and elliptical cross sections, and will be offset at different distances from a wall or free surface. A world-class time resolved tomographic particle image velocimetry system (TR-Tomo-PIV) will be used to perform instantaneous and simultaneous measurements of all three velocity components in three-dimensional domain (3C-3D) on a magnitude that has never before been achieved in the experimental study of turbulent jets adjacent to a wall or free surface. The TR-Tomo-PIV is the latest evolution of PIV, a technique that has revolutionized the experimental study of turbulent flows. The 3C-3D databases will be used to calculate all the mean velocities and higher turbulence statistics, and to perform proper orthogonal decomposition of the proposed turbulent jets. The decay and spread rates will be evaluated to assess how changes in nozzle geometry or offset distance from a boundary affect the mixing characteristics of turbulent jets. ***The jets identified in this proposal are more complex than the canonical shear flows being simulated in the turbulence modelling community, and will represent acute test cases for numerical models. The experimental results will also facilitate the development of more effective second-moment closures, which too often have not been validated against full field measurements. These new models will enable the engineering community to reduce its reliance on physical model testing and design high performance fluid systems. The improved understanding acquired from this research and the new numerical models will lead to the development of innovative technologies and design of energy efficient and environmentally-friendly engineering systems in the aerospace, HVAC and power generation industries.**