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Computational analysis of receptivity and growth mechanisms in laminar boundary layers

层流边界层接受性和生长机制的计算分析

基本信息

批准号：
272465699
负责人：
Dr. Philipp Hack
金额：
--
依托单位：
Center for Turbulence Research
依托单位国家：
德国
项目类别：
Research Fellowships
财政年份：
2015
资助国家：
德国
起止时间：
2014-12-31 至 2015-12-31
项目状态：
已结题

来源：
https://gepris.dfg.de/gepris/projekt/272465699?language=en
关键词：
Computational analysis receptivity growth mechanisms

项目摘要

The relationship between free-stream vortical disturbances and the resulting perturbations in boundary layers is investigated. For example in the flow through turbines, the presence of external disturbances induces a rapid breakdown process, commonly known as bypass transition, which transforms the orderly laminar flow into a chaotic turbulent state. Turbulent flows are associated with increased levels of viscous drag and often entail lower efficiency. In order to optimize efficiency, the design process of airfoils thus often aims to delay transition to turbulence as far as possible. In other cases, such as heat exchangers, it is sought to efficiently obtain a turbulent state while keeping viscous losses at a minimum. By means of an optimization approach, the present study identifies for the first time the most dangerous external disturbances, which are most effective in triggering the amplification of perturbations in pre-transitional boundary layers. This improved knowledge about the flow physics of transition due to external disturbances can help to improve efficiency and reduce emissions in a wide range of applications. Furthermore, the computational framework developed in this context will provide the basis for software tools which can be directly integrated into the industrial design process and which predict the potential for perturbation growth due to external disturbances in various flow configurations.

研究了自由流涡旋扰动和由此产生的边界层扰动之间的关系。例如，在通过涡轮机的流动中，外部扰动的存在会引起快速崩溃过程，通常称为旁路转变，它将有序层流转变为混乱的湍流状态。湍流与粘性阻力水平的增加有关，并且通常会导致效率降低。因此，为了优化效率，翼型的设计过程通常旨在尽可能延迟向湍流的转变。在其他情况下，例如热交换器，寻求有效地获得湍流状态，同时将粘性损失保持在最低限度。通过优化方法，本研究首次确定了最危险的外部扰动，这些扰动在触发过渡前边界层扰动放大方面最有效。对外部扰动引起的过渡流动物理学的了解有助于提高各种应用的效率并减少排放。此外，在此背景下开发的计算框架将为软件工具提供基础，这些软件工具可以直接集成到工业设计过程中，并预测由于各种流动配置中的外部扰动而导致扰动增长的可能性。