Multiscale Simulations of Multiphase Flows

1335913PI：近二十年来，TryggvasonDirect数值模拟（DNS）对我们对多相流的理解做出了重大贡献。随着它们的使用增加，以及对日益复杂的系统进行审查，出现了两个主要问题。首先，在许多情况下，出现的小规模特征需要过多的（通常是无法实现的）分辨率。这些特征要么是自发地以薄膜或线的形式出现，要么是由于在时间和长度尺度上发生的新物理特性的增加，而这些物理特性与流动的物理特性截然不同。第二个问题是，DNS生成的大量数据现在远远超过了用于平均流场的标准模型的数据。本项目旨在通过以下两个目标来解决这两个问题。(1)利用嵌入式解析描述准确捕捉多相流模拟中的拓扑变化。该方法基于这样的观察，即许多小尺度特征（薄膜、线、边界层等）具有相对简单的结构，因此可以通过与完全解析的大尺度运动同时发展的解析或半解析模型来相对准确地描述。在这个项目中，早期的薄膜和传质工作将被扩展，以准确地捕捉薄膜和螺纹的断裂。(2)探索描述复杂多相流拓扑结构的各种先进统计方法的演变。这些量包括面积浓度张量、平均表面张力效应和其他尚未确定的量。目标是建立这些数量与流的结构之间的关系，并试图建立它们的演化模型。将特别关注这些量在拓扑变化过程中的变化，它们对流动整体演变的影响，以及准确预测破裂的重要性。数值方法将通过在线存储库提供，同时还将提供关于方法和代码使用的详细文件。多相流在能量转换、材料加工、化学工业、大气过程和生命系统中都是至关重要的。这些过程效率的逐步提高转化为数十亿美元的节省，新发现有可能改变整个行业。计算研究将为多相系统的管理带来渐进式和变革性的变化。将开发旨在降低新研究人员进入门槛的教育材料，本科生将通过研究项目接触该地区。本项目部分由CISE/ACI CIF21软件重用风险基金资助。

1335913PI: TryggvasonDirect numerical simulations (DNS) have made significant contribution to our understanding of multiphase flows over the last two decades. As their use has increased, and increasingly complex systems are being examined, two major issues have emerged. The first is that in many situations small-scale features emerge that require excessive (and often unachievable) resolution. These features either emerge spontaneously as thin films or threads or due to the addition of new physics that takes place on time and length scales very different than those of the flow. The second issue is that the wealth of data generated by DNS now far outstrips what can be used in standard models for the average flow field. This project is aimed at addressing both issues through the following two objectives. (1) The use of embedded analytical description for accurate capture of topology changes in simulations of multiphase flows. The approach is based on the observation that many small-scale features (films, threads, boundary layers, etc.) have a relatively simple structure and can therefore be described relatively accurately by analytical or semi-analytical models that are evolved concurrently with the fully resolved larger-scale motion. In this project, earlier work of films and mass transfer will be extended to capture accurately the rupture of films and threads. (2) Explore the evolution of various advanced statistical ways to describe the topology of complex multiphase flows. Such quantities include the area concentration tensor, average surface tension effects, and others, yet to be determined. The goal is to establish how these quantities correlate with the structure of the flow, and to attempt to model their evolution. Particular attention will be focused on how these quantities change during topology changes, their influence on the overall evolution of the flow, and the importance of predicting rupture accurately. The numerical methods will be made available through an online repository, along with a thorough documentation of the methodology and the use of the codes.Multiphase flows are critical in energy conversion, material processing, chemical industry, atmospheric processes, and living systems. Incremental improvement in the efficiency of such processes translates into billions of dollars in savings and new discoveries have the potential to transform whole industries. Computational studies will bring about both incremental and transformative changes in the management of multiphase systems. Educational material aimed at lowering the barrier to entry for new researchers will be developed and undergraduate students will be exposed to the area through research projects.This project is partially funded by an CISE/ACI CIF21 Venture Fund for Software Reuse.