Friederike Jensen , Michael Sorg , Axel von Freyberg , Nicholas Balaresque , Andreas Fischer
{"title":"Detection of erosion damage on airfoils by means of thermographic flow visualization","authors":"Friederike Jensen , Michael Sorg , Axel von Freyberg , Nicholas Balaresque , Andreas Fischer","doi":"10.1016/j.euromechflu.2023.12.004","DOIUrl":null,"url":null,"abstract":"<div><p>Cavity-type defects on a wind turbine rotor blade due to erosion lead to an sub-optimal boundary layer flow behavior and result in a reduced annual energy production. To enable an indirect defect detection from far distances, with no contact and no wind turbine stop, the thermographic visualization of the defect wake flow is studied. Experimental investigations and complementary flow simulations on two different airfoil shapes show that the detection is possible above a critical Reynolds number. Furthermore, the wake flow depends on multiple influencing quantities such as the airfoil geometry and the associated chord Reynolds number as well as the cavity position, the cavity shape and the associated cavity Reynolds number. Adjacent cavities can also influence the wake flow behavior. For instance, the cavity position has an influence on the turbulent flow region even after the natural laminar–turbulent flow transition line, and many cavities close to each other shift the transition line towards the leading edge. With increasing aspect ratio as well as increasing inflow velocity, the wake flow turbulence and, thus, the visibility of the wake in the thermographic images becomes higher. However, even if the wake flow from the cavity to the transition line is not continuously visible, a change in the natural transition can still be observed. As a result, thermographic flow visualization enables the indirect detection of cavity-type defects on airfoils and can provide further information about the cavity features.</p></div>","PeriodicalId":11985,"journal":{"name":"European Journal of Mechanics B-fluids","volume":null,"pages":null},"PeriodicalIF":2.5000,"publicationDate":"2023-12-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S0997754623001772/pdfft?md5=6ecfd47c4a197f970045b1ef4e95cf7e&pid=1-s2.0-S0997754623001772-main.pdf","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"European Journal of Mechanics B-fluids","FirstCategoryId":"5","ListUrlMain":"https://www.sciencedirect.com/science/article/pii/S0997754623001772","RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q2","JCRName":"MECHANICS","Score":null,"Total":0}
引用次数: 0
Abstract
Cavity-type defects on a wind turbine rotor blade due to erosion lead to an sub-optimal boundary layer flow behavior and result in a reduced annual energy production. To enable an indirect defect detection from far distances, with no contact and no wind turbine stop, the thermographic visualization of the defect wake flow is studied. Experimental investigations and complementary flow simulations on two different airfoil shapes show that the detection is possible above a critical Reynolds number. Furthermore, the wake flow depends on multiple influencing quantities such as the airfoil geometry and the associated chord Reynolds number as well as the cavity position, the cavity shape and the associated cavity Reynolds number. Adjacent cavities can also influence the wake flow behavior. For instance, the cavity position has an influence on the turbulent flow region even after the natural laminar–turbulent flow transition line, and many cavities close to each other shift the transition line towards the leading edge. With increasing aspect ratio as well as increasing inflow velocity, the wake flow turbulence and, thus, the visibility of the wake in the thermographic images becomes higher. However, even if the wake flow from the cavity to the transition line is not continuously visible, a change in the natural transition can still be observed. As a result, thermographic flow visualization enables the indirect detection of cavity-type defects on airfoils and can provide further information about the cavity features.
期刊介绍:
The European Journal of Mechanics - B/Fluids publishes papers in all fields of fluid mechanics. Although investigations in well-established areas are within the scope of the journal, recent developments and innovative ideas are particularly welcome. Theoretical, computational and experimental papers are equally welcome. Mathematical methods, be they deterministic or stochastic, analytical or numerical, will be accepted provided they serve to clarify some identifiable problems in fluid mechanics, and provided the significance of results is explained. Similarly, experimental papers must add physical insight in to the understanding of fluid mechanics.