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模拟和实验研究方案，用于研究自由射流和偏离固壁或自由表面的射流的混合和湍流特性。这些喷射器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了解，并创建一个高质量数据库的储存库，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，以及评价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。在这个为期5年的周期中，将对16名HQP(5名博士、1名硕士和10名学士)进行培训，以进行新的实验和数值模拟，使他们能够对湍流射流有一个透彻的了解。他们将培养技能，为在学术界或对加拿大具有社会经济重要性的不同行业就业做准备。*喷嘴将由圆形、矩形和椭圆形横截面制造，并将在与墙壁或自由表面不同的距离处进行偏移。世界一流的时间分辨层析粒子图像测速系统(TR-Tomo-PIV)将被用来在三维域(3C-3D)中进行所有三个速度分量的瞬时和同时测量，其量级是在壁面或自由表面附近的湍流射流的实验研究中从未达到的。TR-TOMO-PIV是PIV的最新发展，PIV是一种彻底改变了湍流实验研究的技术。3C-3D数据库将被用来计算所有的平均速度和更高的湍流统计数据，并对所提出的湍流射流进行适当的正交分解。将评估衰减率和扩散率，以评估喷嘴几何形状或距边界的偏移距离的变化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型界正在模拟的正则剪切流更复杂，并将代表数值模型的尖锐测试案例。实验结果还将有助于开发更有效的二次力矩闭合，而这种闭合往往没有得到全场测量的验证。这些新模型将使工程界能够减少对物理模型测试的依赖，并设计高性能流体系统。从这项研究和新的数值模型中获得的更好的理解将导致在航空航天、暖通空调和发电行业开发创新技术和设计节能和环保的工程系统。

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.**