Enhanced Mixing by Vortex Dynamics

湍流混合是多种现象的控制过程，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。它涉及外来物种在湍流载体流体中的夹带和混合，其中被混合的物种可能与载体处于相同或不同的阶段。生成、控制和模拟混合过程到分子水平的能力具有基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限度地提高燃料-空气混合速率和均匀性的能力。尽管由于全球变暖的威胁，这一领域的发展迫切需要，但由于缺乏对气体、液滴和颗粒如何在湍流中运输和混合的了解，这一领域的进展目前受到阻碍。经典的混合观将被混合的物质视为湍流载流中的被动标量，因此标量与速度场相关，速度场由Kolmogorov级联理论的概念控制。然而，越来越多的使用先进激光诊断的实验研究表明，这种传统的混合概念框架是不够的。这类研究通常是为了理解基本现象，如简单流动中偏离高斯行为，但也需要将最新的实验技术应用于更复杂的流动，这些流动更接近实际的混合装置。这一建议概述了一系列的实验，旨在开发一种流动控制装置，以增强混合，被称为涡流发生器。涡旋发生器在混合增强中的应用是全新的，其作为混合器的性能将与横流中的射流进行比较。通过在尽可能小的尺度上研究单相和两相流动，将揭示湍流混合的基本方面，包括漩涡动力学，这不仅将促进对混合过程的理解，而且将有助于未来混合技术的发展。

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.