Multiscale Simulations of Multiphase Flows

多相流的多尺度模拟

• 批准号: 1033478
• 负责人: Gretar Tryggvason
• 金额: $ 30万
• 依托单位: Worcester Polytechnic Institute
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2010
• 资助国家: 美国
• 起止时间: 2010-07-15 至 2011-04-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1033478&HistoricalAwards=false
• 关键词: Multiscale; Simulations; Multiphase; Flows; Multiscale; Simulations; Multiphase; Flows

Direct numerical simulations (DNS) are perhaps the biggest new development in studies of multiphase flows and such simulations are already starting to have a major impact. As their use has increased, it has become clear that in many situations the formation of small-scale features such as thin films or drops require excessive (and often unachievable) resolution. Here it is proposed to develop multi-scale direct numerical simulations to allow the inclusion of such small scale phenomenon in simulations where everything else is fully resolved. The proposed work has the following objectives:The development of a general strategy to include multi-scale description of small-scale phenomenon in numerical simulations of the dynamics of multiphase flows. The approach is based on the observation that many small-scale features (films, threads, boundary layers, strained advection-diffusion reaction layers, very small drops and bubbles, and so on) 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. The challenges include identifying when and where to use such a description, how to efficiently and accurately couple the small-scale description and the numerically resolved flow, and the development of efficient data structures to implement the different descriptions in a way that does not overwhelm developers of such codes.The development of specific multi-scale descriptions for thin films and threads, mass transfer, and chemical reactions to describe under-resolved features in direct numerical simulations of multifluid and multiphase flows. The need for multi-scale approach in these situations arises both because very thin films and threads can form naturally in multiphase flows, and since there is usually a large discrepancy between the length and time scales of the fluid motion on the one hand and mass transfer and reactions on the other. This work, which can be divided into the modeling of small scale flow features (films and threads), thin boundary layers in mass transfer problems, and reaction layers, will build on ideas currently being developed for boiling and an approach originally developed some time ago in the context of modeling of diffusion gas flames, where we showed that we could capture reasonably complex chemical reactions using a surprisingly simple approximation strategy. 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.The intellectual merit of the proposed activity: While direct numerical simulations (DNS) of multiphase flows have already had major impact on our understanding of such flow, and many opportunities still exist for applications of currently existing methods, it is also clear that in many cases the range of scales is too large to handle within the same numerical approach, even using adaptive grid refinement. Small-scale features in multiphase flows do, however, often exhibit a relatively simple structure that can be captured analytically or semi-analytically. In the present work we propose to extend DNS to include such multi-scale descriptions. This will greatly extend the range of multiphase flows that can be studied using DNS. It will, in particular, allow us to consider reacting systems for a realistic range of governing parameters.The broader impacts of the proposed activity: Multiphase flows are critical in energy conversion, material processing, the 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. Enlarging the community of users by providing online codes and documentations will help make that happen. In addition to training graduate students and postdocs, this project will provide research opportunities for undergraduate students.

直接数值模拟（DNS）可能是多相流研究中最大的新发展，并且此类模拟已经开始产生重大影响。随着它们使用的增加，很明显，在许多情况下，小规模特征（例如薄膜或滴剂）的形成需要过多（通常是无法实现的）分辨率。在这里，提议开发多尺度的直接数值模拟，以允许将如此小的现象纳入其他所有内容都完全解决的模拟中。拟议的工作具有以下目标：开发一般策略，在数值模拟的多相流数值中，将小规模现象的多尺度描述包括在内。该方法基于这样的观察结果，即许多小规模特征（膜，线，边界层，紧张的对流扩散反应层，非常小的滴和气泡等）具有相对简单的结构，因此可以通过分析或半分析模型相对准确地描述，这些模型与完全分解的较大较大的尺度运动共同进化。挑战包括确定何时何地使用此类描述，如何有效，准确地将小规模的描述和数值解决流以及有效的数据结构的发展开发，以使这些代码的开发者的开发方式不层压开发。多流体和多相流。在这些情况下，需要多尺度方法的需求既出现了，既可以在多相流中自然形成，并且由于一方面流体运动的长度和时间尺度之间通常存在很大的差异，另一方面是对另一方面的反应。这项工作可以分为小规模流量特征（薄膜和线程），质量转移问题中的薄边界层以及反应层的薄边界层，将建立在目前正在开发的沸腾的想法上，并且最初在建模扩散气体火焰建模的情况下开发了一种方法，我们表明我们可以在其中使用令人惊讶的简单近似近似策略来捕获合理的复杂化学反应。数值方法将通过在线存储库获得，以及对代码的方法和使用的透彻文档。拟议活动的直接数值模拟（DNS）的智力优点已经对我们对这种流程的理解也具有重大影响，并且在许多情况下仍然存在许多范围，它在许多情况下仍然存在许多范围，即使范围也是如此，它甚至是范围的范围。自适应网格细化。但是，多相流中的小规模特征确实表现出相对简单的结构，可以在分析或半分析上捕获。在目前的工作中，我们建议将DNS扩展到包括此类多规模描述。这将大大扩展可以使用DNS研究的多相流的范围。特别是，它将允许我们考虑为现实的管理参数范围的反应系统。拟议活动的更广泛影响：多相流对能量转换，材料加工，化学工业，化学工业，大气过程和生活系统至关重要。此类过程效率的增量提高转化为数十亿美元的储蓄，而新发现有可能改变整个行业。 计算研究将带来多相系统管理的增量和变革性变化。通过提供在线代码和文档来扩大用户社区将有助于实现这一目标。除了培训研究生和博士后，该项目还将为本科生提供研究机会。