Enhanced Mixing by Vortex Dynamics

湍流混合是各种现象的控制过程，包括天气模式、排气烟囱中污染物的扩散、对流传热和湍流燃烧。它涉及在湍流载体流体中夹带和混合外来物质，其中被混合的物质可以与载体处于相同或不同的相。产生、控制和模拟分子水平的混合过程的能力具有根本的科学和技术重要性。例如，燃气轮机低排放燃烧技术的发展取决于最大化燃料-空气混合速率和均匀性的能力。尽管由于全球变暖的威胁，迫切的环境需要这样的发展，在这一领域的进展是目前阻碍了缺乏了解的气体，液滴和颗粒是如何运输和混合在湍流。混合的经典观点对待的物种被混合作为一个被动标量内的湍流载体流体，因此标量与由柯尔莫哥洛夫级联理论的概念支配的速度场相关。然而，越来越多的实验研究使用先进的激光诊断表明，这种传统的概念框架的混合是不够的。这类研究通常是为了了解基本现象，如简单流动中高斯行为的偏离，但也需要将最新的实验技术应用于更复杂的流动，这更接近于实际的混合装置。该提案概述了一系列实验，旨在开发一种用于增强混合的流动控制装置，称为涡流发生器。在增强混合的背景下使用涡流发生器是完全新颖的，它们作为混合器的性能将与横流中的射流进行比较来评估。通过在尽可能小的尺度上研究单相和两相流动，将揭示涉及涡动力学的湍流混合的基本方面，这不仅将促进对混合过程的理解，而且将有助于混合技术的未来发展。

Turbulent mixing is the governing process for a wide variety of phenomena including weather patterns, the dispersion of pollutants from an exhaust stack, convective heat transfer and turbulent combustion. It involves the entrainment and mixing of a foreign species in a turbulent carrier fluid, where the species being mixed may be in the same or different phase from the carrier. The ability to generate, control, and model mixing processes down to the molecular level is of fundamental scientific and technical importance. For example, the development of low-emission combustion technologies for gas turbines depends on the ability to maximise the rate and uniformity of fuel-air mixing. Despite the pressing environmental need for such development due to the threat of global warming, progress in this area is currently hampered by a lack of understanding of how gases, droplets and particles are transported and mixed in turbulent flows.The classical view of mixing treats the species being mixed as a passive scalar within the turbulent carrier fluid, so that the scalar is correlated to the velocity field which is governed by the concepts of the Kolmogorov cascade theory. However, an increasing body of experimental research using advanced laser diagnostics suggests that this traditional conceptual framework for mixing is inadequate. Studies of this kind are typically directed towards understanding fundamental phenomena such as departures from Gaussian behaviour in simple flows, but there is also a need to apply the latest experimental techniques to more complex flows, which are closer to practical mixing devices. This proposal outlines a series of experiments which aim to develop a flow control device for enhanced mixing, known as a vortex generator. The use of vortex generators in the context of mixing enhancement is entirely novel, and their performance as mixers will be evaluated in comparison with jets in cross-flow. By studying both single-and two-phase flows at the smallest possible scales the fundamental aspects of turbulent mixing involving vortex dynamics will be brought to light, which will not only advance the understanding of mixing processes but will also contribute to the future development of mixing technologies.