Collaborative Research: Droplet breakup in homogenous turbulence: model validation through experiments and direct numerical simulations

液滴在湍流流动中的破碎是许多工程、科学和环境应用中的重要现象。例如，许多化学和制药加工技术涉及在成分混合和反应时液滴破碎。液滴破碎在环境应用中也很重要，例如石油泄漏的动态及其清理，以及地下储罐泄漏到水源中。科学家和工程师一直致力于开发预测复杂流体过程的计算技术，如上面列出的那些。这些计算技术的一个关键组成部分是准确描述液滴破碎及其对流动参数(如湍流强度)和液滴特性(如粘度、表面张力、直径和密度)的依赖关系的模型。该项目将进行一系列实验，以测量高度受控条件下的液滴破碎情况。实验数据将用于改进液滴破碎模型。本项目将通过进行详细的实验，并使用这些数据来改进和验证液滴破碎模型，来研究湍流强度和流体性质对液滴破碎的影响。在实验中，单个液滴将被注入到一个设计成产生均匀湍流场的流室中。用粒子图像测速仪对湍流场进行了表征。当液滴变形并被湍流打破时，将会拍摄到高速电影。这些实验将针对不同的液滴直径和流体重复进行，并将对大型液滴破碎电影进行统计分析，以获得有关液滴破碎过程的数据，包括液滴的大小和形状。此外，由于电影中的连续图像的定时将是已知的，因此可以通过分析每个图像序列来确定液滴破碎事件的定时和频率。研究生和本科生将在这个项目上工作。艾姆斯(爱荷华州)高中强化学习计划将招募当地高中生作为研究团队的一部分。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。

The breakage of liquid droplets in a turbulent fluid flow is an important phenomenon in numerous engineering, scientific, and environmental applications. For example, many chemical and pharmaceutical processing techniques involve droplets breaking as components mix and react. Droplet breakage is also important in environmental applications such as the dynamics of oil spills and their cleanup, and in the leakage of underground storage tanks into water sources. Scientists and engineers have worked to develop computational techniques to predict complex fluid processes such as those listed above. A key component of these computational techniques are models that accurately describe droplet breakage and its dependence on flow parameters such as turbulence intensity and droplet properties such as viscosity, surface tension, diameter, and density. This project will conduct a series of experiments to measure droplet breakage under highly controlled conditions. Data from the experiments will be used to improve droplet breakage models.This project will investigate effects of turbulence intensity and fluid properties on droplet breakage by performing detailed experiments and using these data to improve and validate droplet breakage models. In the experiments, individual droplets will be injected into a flow chamber that has been designed to generate a uniform turbulent field. The turbulent field will be characterized using particle image velocimetry. High-speed movies will be captured of the droplet as it is deformed and then broken by the turbulence. The experiments will be repeated for different droplet diameters and fluids, and large ensembles of droplet breakage movies will be analyzed statistically to yield data on the droplet breakup process, including droplet size and shape. Moreover, because the timing of successive images in the movies will be known, droplet breakage event timings and frequencies can be determined by analyzing each image sequence. Graduate and undergraduate students will work on this project. Local high-school students will be recruited to participate as part of the research team through the Ames (Iowa) High School Enhanced Learning Program.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.