Collaborative Research: Correlating Large-Scale Visual Structures to Entrainment Mechanisms in Buoyant and Momentum-Driven Plumes

这项研究将探索浮力羽流的发展，特别是量化沿羽流/环境界面发展的物理结构如何导致通过出口的质量传输，以及这些结构随后如何影响卷吸和混合。这项工作将揭示羽流演化中的机制差异，这取决于来源条件，从而为传输模型适当地纳入这些现象的物理学提供信息。这是了解和预测来自羽流的营养物质或污染物的命运的关键--例如，火山灰云、排放到海湾或河口的污染物，以及许多其他环境和工业流动。虽然流体力学学界早已认识到湍流中涡旋的物理长度范围，但缺乏关于羽流或喷流的外部结构如何与源条件相联系的研究。通过这项研究发现的知识将为通过对远程获取的数据进行图像分析来量化羽流动力学提供强有力的手段。这项研究将支持两名研究生和本科生研究人员的培养。研究小组将为当地的外展和教育项目开发研讨会，外展活动的数据将用于研究任务。最后，这个项目将成为世界卫生组织地球物理流体动力学暑期项目研究生项目的基础。将进行实验室实验和直接数值模拟，以满足两个主要目标。第一个目标是开发技术，以确定和量化组成羽流结构的特征，以便从录像或摄影记录中远程确定工业或天然羽流的来源条件。第二个目标是研究羽流/环境界面的混合和卷吸机制。在实验室实验中，将同时使用时空分辨粒子图像测速技术和激光诱导荧光测量技术分别对流场和传质进行量化。时间推移立体摄影测量将用于重建羽流的动态三维外缘，由此可以表征组成外部结构的长度尺度的分布。一套补充的直接数值模拟将在静止的未分层和分层的背景流体中进行。模拟数据将确定湍流/非湍流界面以及驱动羽流边缘卷吸和混合的结构，并随后将其与实验室数据进行比较。这项研究将提高我们在羽流驱动的现象期间确定源条件的能力，这些现象包括但不限于火山喷发、森林火灾、冰川排放羽流、海底扩散和疾病传播。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

This research will explore the development of buoyant plumes, specifically to quantify how physical structures that develop along the plume/ambient interface result from mass transport through an outlet, and how these structures subsequently affect entrainment and mixing. This work will uncover mechanistic differences in plume evolution, depending on source conditions, thus informing transport models to appropriately incorporate physics for these phenomena. This is key to understanding and predicting the fate of nutrients or pollutants from plumes – for example, volcanic ash clouds, discharges into bays or estuaries, and a host of other environmental and industrial flows. While the fluid dynamics community has long acknowledged the range of physical length scales of eddies in turbulent flows, there exists a lack of research regarding how the exterior structure of a plume or jet is linked to the source conditions. Knowledge uncovered through this research will provide robust means for quantifying plume dynamics through image analysis of remotely acquired data. The research will support the training of two graduate students and undergraduate researchers. The research team will develop workshops for local outreach and educational programs, and data from the outreach events will be used in the research mission. Finally, this project will form the basis for a project for a graduate student in the WHOI summer program in Geophysical Fluid Dynamics.Laboratory experiments and direct numerical simulations will be conducted to satisfy two primary objectives. The first goal is to develop techniques to identify and quantify features comprising the plume structure to remotely determine source conditions of industrial or natural plumes from video or photographic recordings. The second goal is to investigate mechanisms of mixing and entrainment at the plume/ambient interface. In laboratory experiments, simultaneous spatio-temporally resolved particle image velocimetry and laser induced fluorescence measurements will be used to quantify the flow field and mass transport, respectively. Time lapse stereo photogrammetry will be used to reconstruct the dynamic three-dimensional outer edge of the plume, from which distributions of the length scales comprising the external structure can be characterized. A complementary suite of direct numerical simulations will be performed in quiescent unstratified and stratified background fluids. The turbulent/non-turbulent interface and the structures driving entrainment and mixing at the plume edges will be identified in the simulation data and subsequently be compared to the laboratory data. This research will enhance our ability to determine source conditions during plume-driven phenomena, including but not limited to volcanic eruptions, forest fires, glacial discharge plumes, undersea dispersion, and disease transmission.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.