Passive and Active Flow-Control in the Turbulent Three-Dimensional Wall Jet

人们普遍认为，在看似随机的湍流之下，有组织的湍流运动仍然存在。这些有组织的运动或连贯的结构与许多工程性质有关，如阻力、传热或噪音产生。目前的研究计划旨在提高我们对如何通过被动和主动手段控制这些相干结构的理解，以产生有用的工程结果，如减少阻力，增强传热和减少噪音排放。像这样的流量控制技术有可能每年节省数十亿美元的燃料，并产生更经济、更环保的工业过程。本文的研究目的是通过实验控制三维壁面射流中的相干结构，通过主动和被动的方法来减少和增强流动的横向发展。这两种结果在许多实际应用中都很有用。特别是，在需要大面积传热的情况下，增强射流的表面覆盖是有利的，而减少射流的横向发展可能会增强混合并在燃烧应用中有用。利用我们对射流中有组织的湍流运动的现有知识，研究的第一阶段将采用被动控制技术（如涡流发生器）来控制射流的横向发展。研究的第二阶段旨在开发先进的反应式流动控制能力，并将通过多点壁面压力测量来提高我们的流量传感能力。

It is generally accepted that organized turbulent motions persist beneath seemingly random turbulent flows. These organized motions, or coherent structures are linked to many properties of engineering interest, like drag, heat-transfer or noise production. The present research program is aimed at improving our understanding of how to control these coherent structures by both passive and active means to produce useful engineering results like drag-reduction, enhanced heat-transfer, and reduced noise emissions. Flow-control techniques like these have the potential to save billions of dollars in annual fuel savings and produce more economical and environmentally friendly industrial processes. The objective of the proposed research is to experimentally control the coherent structures in a three-dimensional wall jet by both active and passive means to reduce and enhance the lateral development of the flow. Both outcomes are useful in many practical applications. In particular, enhancing surface coverage of the jet is advantageous where large areas heat-transfer are required, whereas, reducing the lateral development of the jet will likely enhance mixing and be useful in combustion applications. Using our existing knowledge of the organized turbulent motions in the jet, the first phase of the research will employ passive control techniques (like vortex generators) to control the lateral development of the jet. The second phase of the research is aimed at working towards advanced reactive flow control capabilities and will improve our flow sensing capabilities using multi-point wall pressure measurements.