Influence of roughness-generated streaks on laminar separation bubbles

IF 2.3 3区 工程技术 Q2 ENGINEERING, MECHANICAL
Tomek Jaroslawski, Maxime Forte, Olivier Vermeersch, Jean-Marc Moschetta, Erwin Gowree
{"title":"Influence of roughness-generated streaks on laminar separation bubbles","authors":"Tomek Jaroslawski,&nbsp;Maxime Forte,&nbsp;Olivier Vermeersch,&nbsp;Jean-Marc Moschetta,&nbsp;Erwin Gowree","doi":"10.1007/s00348-024-03837-6","DOIUrl":null,"url":null,"abstract":"<div><p>This experimental investigation studies the impact of streaks on two-dimensional laminar separation bubbles forming over an aerofoil. Streaks are introduced into the boundary layer using cylindrical roughness elements, and the resulting mean and unsteady flow fields are measured using hotwire anemometry. The observed streaks generated by roughness exhibit analogous behaviour to those generated by freestream turbulence, significantly altering the mean flow characteristics of the bubble, including reductions in its length, height, and the introduction of spanwise velocity gradients. These mean flow modifications have a damping effect on convective disturbance growth. The experiments suggest the coexistence of modal instability due to the laminar separation bubble and transient growth due to streaks. To investigate the combined effect of roughness and the presence of freestream turbulence, we increase the turbulence level from the baseline in the presence of a roughness forcing configuration. We find that increasing the turbulence intensity leads to an enhancement of transient growth, accompanied by distinctive chordwise disturbance growth compared to lower freestream turbulence intensity levels.</p></div>","PeriodicalId":554,"journal":{"name":"Experiments in Fluids","volume":"65 7","pages":""},"PeriodicalIF":2.3000,"publicationDate":"2024-07-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"Experiments in Fluids","FirstCategoryId":"5","ListUrlMain":"https://link.springer.com/article/10.1007/s00348-024-03837-6","RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q2","JCRName":"ENGINEERING, MECHANICAL","Score":null,"Total":0}
引用次数: 0

Abstract

This experimental investigation studies the impact of streaks on two-dimensional laminar separation bubbles forming over an aerofoil. Streaks are introduced into the boundary layer using cylindrical roughness elements, and the resulting mean and unsteady flow fields are measured using hotwire anemometry. The observed streaks generated by roughness exhibit analogous behaviour to those generated by freestream turbulence, significantly altering the mean flow characteristics of the bubble, including reductions in its length, height, and the introduction of spanwise velocity gradients. These mean flow modifications have a damping effect on convective disturbance growth. The experiments suggest the coexistence of modal instability due to the laminar separation bubble and transient growth due to streaks. To investigate the combined effect of roughness and the presence of freestream turbulence, we increase the turbulence level from the baseline in the presence of a roughness forcing configuration. We find that increasing the turbulence intensity leads to an enhancement of transient growth, accompanied by distinctive chordwise disturbance growth compared to lower freestream turbulence intensity levels.

Abstract Image

Abstract Image

粗糙度产生的条纹对层流分离气泡的影响
本实验研究了条纹对在气膜上形成的二维层流分离气泡的影响。使用圆柱形粗糙度元素将条纹引入边界层,并使用热线风速计测量由此产生的平均流场和非稳定流场。观察到的粗糙度产生的条纹与自由流湍流产生的条纹表现出类似的行为,极大地改变了气泡的平均流动特性,包括气泡长度和高度的减少,以及跨向速度梯度的引入。这些平均流的改变对对流扰动的增长具有抑制作用。实验表明,层流分离气泡导致的模态不稳定性和条纹导致的瞬态增长并存。为了研究粗糙度和自由流湍流的综合影响,我们在粗糙度强迫配置的情况下,在基线的基础上增加了湍流水平。我们发现,与较低的自由流湍流强度相比,湍流强度的增加会导致瞬态增长的增强,并伴随着明显的弦向扰动增长。
本文章由计算机程序翻译,如有差异,请以英文原文为准。
求助全文
约1分钟内获得全文 求助全文
来源期刊
Experiments in Fluids
Experiments in Fluids 工程技术-工程:机械
CiteScore
5.10
自引率
12.50%
发文量
157
审稿时长
3.8 months
期刊介绍: Experiments in Fluids examines the advancement, extension, and improvement of new techniques of flow measurement. The journal also publishes contributions that employ existing experimental techniques to gain an understanding of the underlying flow physics in the areas of turbulence, aerodynamics, hydrodynamics, convective heat transfer, combustion, turbomachinery, multi-phase flows, and chemical, biological and geological flows. In addition, readers will find papers that report on investigations combining experimental and analytical/numerical approaches.
×
引用
GB/T 7714-2015
复制
MLA
复制
APA
复制
导出至
BibTeX EndNote RefMan NoteFirst NoteExpress
×
提示
您的信息不完整,为了账户安全,请先补充。
现在去补充
×
提示
您因"违规操作"
具体请查看互助需知
我知道了
×
提示
确定
请完成安全验证×
copy
已复制链接
快去分享给好友吧!
我知道了
右上角分享
点击右上角分享
0
联系我们:info@booksci.cn Book学术提供免费学术资源搜索服务,方便国内外学者检索中英文文献。致力于提供最便捷和优质的服务体验。 Copyright © 2023 布克学术 All rights reserved.
京ICP备2023020795号-1
ghs 京公网安备 11010802042870号
Book学术文献互助
Book学术文献互助群
群 号:481959085
Book学术官方微信