Dynamics of Geysers in Stormsewer Systems and Novel Retrofitting Methods

联合污水溢流(CSO)是指当系统被填满时，将未经处理的污水和雨水排放到接收水道中。民间社会组织是全美860个城市水污染的主要来源。联合下水道系统由一个深层隧道网络组成，用于输送雨水和污水。在降雨期间，这些系统可以迅速被雨水填满，导致大量空气被困住。当滞留的空气通过竖井释放时，间歇喷泉经常会喷发。这些间歇泉的高度可以超过30米，并可能导致大规模洪水事件，导致小溪、河流和湖泊受到污染。许多联合下水道系统的运行低于设计能力，以防止在降雨期间形成间歇泉，但这增加了公民社会组织的可能性。这一研究项目将从机理上理解间歇泉的形成，可用于设计竖井的改造方法，从而在不产生间歇泉的情况下顺利释放气囊。当间歇泉不再是一个令人担忧的问题时，雨水渠系统的全部容量可以在下雨期间得到充分利用，因此CSO的排放量将大大减少。一项外展计划将教育和培训研究人员、来自代表性不足群体的中学生和大学生、下水道系统运营商和其他利益攸关方，了解间歇泉的控制和民间社会组织对水质的影响。该研究项目的目标是对在雨水下水道系统中触发间歇喷泉的两相流物理有一个基本的了解。这项研究将利用集成的高速光学成像、数字粒子图像测速和三维计算流体力学来模拟和确认实验室规模的间歇泉复制结果。将进行研究，以了解间歇泉喷发、系统几何形状和初始流动条件之间的关系。将根据这些关系开发一个降阶间歇泉模型，并以开放源码软件格式实施，用于模拟暴雨下水道系统中的水流动力学。允许气囊平稳释放的改装策略将使用3-D模型进行初步测试和验证，最有希望的方法将进行实验测试和数值验证。这项研究的结果将被科学家、水利工程师和其他从业者用来为未来的设计和翻新战略提供参考，以防止暴雨下水道系统中间歇泉的形成。学生、监管机构和其他利益相关者将从这些软件包和教育宣传中了解如何防止间歇泉形成，减少民间社会组织及其对环境的相关影响。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。

Combined sewer overflows (CSOs) are the release of raw sewage and stormwater into receiving waterways when the system becomes filled. CSOs constitute a major source of water pollution for 860 municipalities across the United States. Combined sewer systems consist of a network of deep tunnels to move both stormwater and sewage. These systems can be filled rapidly with stormwater during rainfall events, resulting in the entrapment of large amounts of air. When the trapped air is released through vertical drop shafts, geyser eruptions are often produced. These geysers can exceed 30 meters in height and can cause massive flooding events that lead to the pollution of streams, rivers, and lakes. Many combined sewer systems are operated below design capacity to prevent geyser formation during rain events, but this increases the likelihood of CSOs. This research project will develop a mechanistic understanding of geyser formation that can be used to design retrofitting methods for drop shafts that allow the smooth release of air pockets without producing geysers. When geysers are no longer a concern, the full capacity of storm sewer systems can be utilized during rain events and hence CSO discharges will be reduced significantly. An outreach program will educate and train researchers, middle-school and college students from underrepresented groups, sewer system operators, and other stakeholders on the control of geysers and the impact of CSOs on water quality. The goal of the research project is to develop a fundamental understanding of the two-phase flow physics that triggers geysering in storm sewer systems. The research will utilize integrated high-speed optical imaging, digital particle image velocimetry, and 3-D computational fluid dynamics to model and confirm results from the laboratory-scale reproduction of geysers. Studies will be performed to understand the relationship between geyser eruption, system geometry, and initial flow conditions. A reduced order geyser model will be developed from these relationships and implemented in an open-source software format for modeling flow dynamics in storm sewer systems. Retrofitting strategies to permit the smooth release of air pockets will be preliminarily tested and validated using a 3-D model, and the most promising methods will be tested experimentally and confirmed numerically. The outcomes of this research will be used by scientists, hydraulic engineers, and other practitioners to inform future design and retrofitting strategies to prevent geyser formation in storm sewer systems. Students, regulators, and other stakeholders will learn from the software packages and educational outreach how to prevent geyser formation and reduce CSOs and their associated impacts on the environment.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.