Turbulent mixing between a shock-accelerated vortex ring and its surroundings

当激波在不同气体占据的区域传播时，它会在波边界产生气体运动，从而导致比没有激波时更高的混合率。这种现象可能发生在一种喷气式发动机中，这种发动机被设计成以比传统喷气式运输机高得多的极高速度运行。研究这类流动通常是非常具有挑战性的，因为流动特性，如速度、局部气体成分和温度，以非常复杂的方式在空间和时间上变化。这个研究项目将研究这种流的一个简单版本。研究人员将研究涡流环对脉冲加速度的响应。根据旋涡环流场的性质，这种初始条件应该包含比喷气发动机更连贯、更有组织、更可预测和可测量的涡度场。结果将形成一个高度精炼的构建块数据库，该数据库可用于开发这些流的更复杂版本的预测能力。研究生和本科生将大量参与研究，通过校园现有的不同项目招募代表性不足的少数民族成员。该项目还将提供教育和接触最先进的技术以及科学和工程领域的一些最新挑战。利用平面激光诱导荧光（PLIF）和粒子图像测速（PIV）技术研究了平面激波与由不同气体组成的涡流环相互作用所引起的湍流混合。该项目的目标是测量一些最相关的流动特性，包括两种气体的浓度和它们在气体混合区域内的速度。这一目标将以两种不同的方式实现：1)测量将在离散的时间瞬间进行，具有非常高的空间分辨率；2)测量将以较小的空间分辨率进行，但使用的成像系统将允许以每秒高达20,000场的速度收集整个浓度场。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

When a shock wave propagates through a region occupied by different gases, it generates gas motions at the wave boundary that lead to mixing at much higher rates than would have occurred in the absence of the shock wave. Phenomena of this kind can occur in a category of jet engines designed to operate at extremely high speeds that are much higher than those used in conventional jet transport. The study of these kinds of flows is generally very challenging because flow properties such as velocity, local gas composition, and temperature vary in space and time in very complicated ways. This research project will study a simple version of this type of flow. The researchers will study the response of a vortex ring to impulsive acceleration. By the nature of the vortex ring flow field, this initial condition should contain a much more coherent, well organized, predictable and measurable vorticity field than that of the jet engine. The results will form a highly refined building block database which could be used to develop a predictive capability for the more complicated version of these flows. Graduate and undergraduate students will be heavily involved in the research, with members of underrepresented minorities recruited through different programs already existing on campus. This project also will provide education in and exposure to state-of-the-art technologies and some of the most current challenges in science and engineering. The turbulent mixing induced by the interaction of a planar shock wave with a vortex ring consisting of a gas different than its surroundings will be investigated using planar laser induced fluorescence (PLIF) and particle image velocimetry (PIV). The goal of the project is to measure some of the most relevant flow properties, including the concentrations of the two gas species and their velocities everywhere within the region where the gases mix. This objective will be pursued in two different ways: 1) measurements will be made at discrete instants in time, with very high spatial resolution, and 2) measurements will be carried out with lesser spatial resolution but using an imaging system that will allow to collect entire concentration fields at a rate of up to 20,000 fields per second.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.