A novel predictive dual scale model to accurately and efficiently simulate phase interfaces in turbulent flows

具有相界面的湍流几乎出现在我们日常生活的各个方面，从使用液体燃料的能源系统到药物喷雾。这些流动中的许多涉及将液体雾化成形成喷雾的小规模液滴。整个系统的性能在很大程度上取决于这种喷雾的质量。例如，在飞机或内燃机中，喷雾质量的改进可以导致效率的提高和污染物产生的减少。在医用喷雾剂中，精确控制气雾剂的喷雾液滴尺寸可以显著改善药物向肺部的输送。不幸的是，目前还没有一个有效的模型，从第一性原理推导出来的，可以预测和模拟复杂的过程中形成的喷雾湍流。因此，增量设计改进理念在许多应用中是普遍的，因为全新设计的实验非常昂贵，并且数值模拟缺乏湍流雾化过程的预测模型，因此需要利用现有的实验数据进行调整。本计画的目标是发展一个有效的预测模式来模拟紊流中的雾化过程。这种模式有可能开创一种大胆的新设计理念，以全新的设计为目标，因为使用新模式进行预选可行性研究的成本将大大低于实验研究。该项目还结合了重要的教育活动，包括本科生研究人员的参与，以及通过校内活动和校外课堂访问针对当地一级学校的外展活动。新模型基于双尺度方法的思想，规避了湍流经典建模方法的局限性，即依赖于从大尺度到小尺度的级联过程的存在。这种级联对于雾化相界面可能并不占主导地位，因为在小尺度上占主导地位的表面张力既可以产生又可以消灭小尺度界面结构。所提出的双尺度方法考虑到这一点，采用多尺度分解，结合直接数值模拟的功能，解决了小尺度与大涡模拟较大尺度的一种有效的方式。这种方法本质上包含了不同的力量和原子化机制之间的相互作用和竞争，作用于多个长度和时间尺度，并通过将显式过滤器应用于解析尺度相界面几何形状，实现了需要在更大尺度上建模的项的显式闭合。该奖项反映了NSF的法定使命，并被认为值得通过使用基金会的智力价值和更广泛的评估来支持。影响审查标准。

Turbulent flows with phase interfaces occur in almost every aspect of our daily lives, ranging from energy systems using liquid fuels to pharmaceutical sprays. Many of these flows involve atomizing a liquid into small-scale drops forming a spray. The performance of the overall system depends strongly on the quality of this spray. For example, in aircraft or internal combustion engines improvements in the quality of the spray can result in efficiency gains and reduction in pollutant production. In medical sprays, precisely controlling the spray drop sizes of aerosols can significantly improve the delivery of pharmaceuticals into the lung. Unfortunately, no efficient model derived from first principle currently exists that can predict and simulate the complex process of spray formation in turbulent flows. Thus an incremental design improvement philosophy is prevalent in many applications because experiments of radically new designs are very costly and numerical simulations lack a predictive model for turbulent atomization processes and thus require tuning with existing experimental data. The goal of this project is to develop an efficient predictive model to simulate atomization processes in turbulent flows. Such a model has the potential to initiate a bold new design philosophy that targets radically new designs because the cost of pre-selection feasibility studies using the new model would be significantly lower than experimental studies. The project also incorporates significant educational activities, including involvement of undergraduate researchers and outreach targeting local Title-One schools through on-campus activities and off-campus classroom visits.The new model is based on the idea of a dual scale approach, circumventing the limitations of classical modeling approaches for turbulent flows that rely on the existence of a cascade process from large to small scales. Such a cascade is likely not dominant for atomizing phase interfaces since surface tension forces that are dominant on the small scale can both generate and annihilate small scale interface structures. The proposed dual scale approach takes this into account by employing a multi-scale decomposition that combines features of direct numerical simulations resolving the small scales with large eddy simulation for the larger scales in an efficient way. This approach inherently incorporates the interaction and competition between different forces and atomization mechanisms acting on multiple length and time scales and enables the explicit closure of terms requiring modeling on the larger scales by applying explicit filters to the resolved scale phase interface geometry.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.