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Modelling of the Unsteady Dynamics of Turbulent Disperse Bubbly Flows

湍流分散气泡流的非定常动力学建模

基本信息

批准号：
290278641
负责人：
Professor Dr.-Ing. Markus Klein
金额：
--
依托单位：
Institut für Angewandte Mathematik und Wissenschaftliches Rechnen (LRT-1)
依托单位国家：
德国
项目类别：
Research Grants
财政年份：
2016
资助国家：
德国
起止时间：
2015-12-31 至 2020-12-31
项目状态：
已结题

来源：
https://gepris.dfg.de/gepris/projekt/290278641?language=en
关键词：
Modelling Unsteady Dynamics Turbulent Disperse

项目摘要

Bubbly flows are found in a large number of industrial processes including oil wells, power generation as well as in the food, pharmaceutical and chemical industry. In this way chemical goods worth billions of dollars are produced worldwide every year. Therefore the advantages of the ability of a reliable numerical simulation tool in regards of process safety and process control are enormous.Typically, two phase flow simulations in industry are based on the Reynolds averaged Navier-Stokes equations (RANS). However even for single phase flow, after decades of research, no satisfactory turbulence closure model is available. Bubbly flows are characterized by spatially and temporally deforming interfaces. The manifold interaction of bubble dynamics, turbulence and the bubbles itself are so complex, that the availability of a universal and accurate RANS model for the prediction of bubbly flows appears unlikely in near future. Large eddy simulation (LES) offers a good compromise between RANS based closures and the direct numerical simulation (DNS) of the underlying equations. Combined with an interface advection technique LES offers the advantage, that many physical processes can be resolved to a large extent which is in contrast to modelling the whole range of length and time scales in RANS. In the context of two phase flows with moving boundaries the LES equations contain additional unknown terms. The development of closures for these terms has just started and no model has been demonstrated in the literature to yield satisfactory results in a real LES, yet. The goal of this project is to establish an LES model which is able to predict disperse bubbly flows of practical interest with good accuracy. The project is subdivided into two phases. First a DNS data base will be generated. To this end vertically rising single bubbles as well as small bubble swarms will be simulated in a quiescent fluid as well as in a turbulent counterflow configuration. Subsequently the data will be filtered to obtain pseudo LES data (a-priori analysis). In this way model ideas can be compared with the exact unclosed terms determined from DNS. The true evaluation of a model requires however to perform a real LES. The models from phase one which appear most promising will be implemented in the LES code and compared with DNS and very detailed experimental data available from a research partner. This so called a-posteriori analysis will guide the qualification of an LES model for bubbly two phase flows. In a continuation of this research project it is planned to use a multiscale approach in order to enable the simulation of large bubble swarms. This will allow to reach the global goal, which is the simulation of configurations of practical interest.

泡沫流存在于许多工业过程中，包括油井、发电以及食品、制药和化学工业。通过这种方式，全世界每年生产价值数十亿美元的化学产品。因此，可靠的数值模拟工具在过程安全和过程控制方面的能力具有巨大的优势。通常，工业中的两相流模拟是基于雷诺平均的纳维斯托克斯方程(RANS)。然而，即使对于单相流，经过几十年的研究，也没有令人满意的湍流闭合模型。泡状流的特征是空间和时间上的变形界面。气泡动力学、湍流和气泡本身的多种相互作用是如此复杂，以至于在不久的将来似乎不太可能有一个通用和准确的RANS模型来预测气泡流。大涡模拟(LES)在基于RANS的闭包和基本方程的直接数值模拟(DNS)之间提供了一个很好的折衷。与界面平流技术相结合，LES提供了一个优势，即许多物理过程可以在很大程度上得到解决，这与在RAN中对整个长度和时间尺度范围进行建模形成了对比。在具有运动边界的两相流背景下，大涡模拟方程包含额外的未知项。针对这些术语的闭包的开发才刚刚开始，目前还没有在文献中演示的模型在实际的LES中产生令人满意的结果。本项目的目标是建立一个大涡模拟模型，该模型能够以较高的精度预测有实际意义的分散泡状流。该项目分为两个阶段。首先，将生成一个域名系统数据库。为此，将在静止流体和湍流逆流结构中模拟垂直上升的单个气泡和小气泡群。随后，数据将被过滤以获得伪LES数据(先验分析)。通过这种方式，可以将模型想法与从域名系统确定的确切未封闭项进行比较。然而，对模型的真正评估需要执行真正的大涡模拟。第一阶段中最有希望的模型将在LES代码中实现，并与DNS和从研究伙伴那里获得的非常详细的实验数据进行比较。这一所谓的后验分析将指导对起泡两相流的大涡模拟进行鉴定。在这项研究项目的继续中，计划使用多尺度方法，以便能够模拟大型气泡群。这将允许达到全局目标，即对实际感兴趣的配置进行模拟。