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

在紊流中液滴的破裂是许多工程、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都涉及到当成分混合和反应时液滴的破裂。液滴破裂在环境应用中也很重要，例如石油泄漏的动力学及其清理，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计算技术来预测复杂的流体过程，如上面列出的那些。这些计算技术的一个关键组成部分是精确描述液滴破裂及其对流动参数（如湍流强度）和液滴特性（如粘度、表面张力、直径和密度）的依赖的模型。该项目将进行一系列实验，在高度控制的条件下测量液滴的破裂。实验数据将用于改进液滴破碎模型。本项目将通过详细的实验研究湍流强度和流体性质对液滴破裂的影响，并利用这些数据改进和验证液滴破裂模型。在实验中，单个液滴将被注入一个设计用于产生均匀湍流场的流室。紊流场将用粒子图像测速法进行表征。高速电影将捕捉到液滴的变形，然后被湍流打破。实验将针对不同直径的液滴和不同流体重复进行，并对液滴破碎膜的大集合进行统计分析，以获得液滴破碎过程的数据，包括液滴的大小和形状。此外，由于电影中连续图像的时间是已知的，因此可以通过分析每个图像序列来确定液滴破裂事件的时间和频率。研究生和本科生将参与这个项目。当地的高中学生将通过艾姆斯（爱荷华州）高中强化学习计划被招募作为研究团队的一部分。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。

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.