Experimental characterization of turbulent boundary layers around a NACA 4412 wing profile

IF 2.8 2区 工程技术 Q2 ENGINEERING, MECHANICAL Experimental Thermal and Fluid Science Pub Date : 2024-10-01 DOI:10.1016/j.expthermflusci.2024.111327
Fermin Mallor , Carlos Sanmiguel Vila , Majid Hajipour , Ricardo Vinuesa , Philipp Schlatter , Ramis Örlü
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Abstract

An experimental characterization of the turbulent boundary layers developing around a NACA 4412 wing profile is carried out in the Minimum Turbulence Level (MTL) wind tunnel located at KTH Royal Institute of Technology. The campaign included collecting wall-pressure data via built-in pressure taps, capturing velocity signals in the turbulent boundary layers (TBLs) using hot-wire anemometry (HWA), and conducting direct skin-friction measurements with oil-film interferometry (OFI). The research spanned two chord-based Reynolds numbers (Rec=4×105 and 106) and four angles of attack (5°, 8°, 11° and 14°), encompassing a broad spectrum of flow conditions, from mild to strong adverse-pressure gradients (APGs), including scenarios where the TBL detaches from the wing surface. This dataset offers crucial insights into TBL behavior under varied flow conditions, particularly in the context of APGs. Key features include the quasi-independence of the pressure coefficient distributions from Reynolds number, which aids in distinguishing Reynolds-number effects from those due to APG strengths. The study also reveals changes in TBL dynamics as separation approaches, with energy shifting from the inner to the outer region and the eventual transition to a free-shear flow state post-separation. Additionally, the diagnostic scaling in the outer region under spatial-resolution effects is considered, showing further evidence for its applicability for small L+, however with inconsistent results for larger L+. The findings and database resulting from this campaign may be of special relevance for the development and validation of turbulence models, especially in the context of aeronautical applications.
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NACA 4412翼型周围湍流边界层的实验特征
在位于 KTH 皇家理工学院的最小湍流水平(MTL)风洞中,对 NACA 4412 翼型周围形成的湍流边界层进行了实验表征。活动包括通过内置压力抽头收集壁压数据,使用热线风速测量法(HWA)捕捉湍流边界层(TBL)中的速度信号,以及使用油膜干涉测量法(OFI)进行直接表皮摩擦测量。研究跨越了两个基于弦线的雷诺数(Rec=4×105 和 106)和四个攻角(5°、8°、11° 和 14°),涵盖了从轻微到强烈逆压梯度 (APG) 的各种流动条件,包括 TBL 脱离翼面的情况。该数据集为了解不同流动条件下的 TBL 行为,尤其是 APGs 背景下的 TBL 行为提供了重要依据。主要特征包括压力系数分布与雷诺数的准无关性,这有助于区分雷诺数效应和 APG 强度效应。研究还揭示了随着分离的临近 TBL 动力学的变化,能量从内部区域转移到外部区域,并最终过渡到分离后的自由剪切流动状态。此外,还考虑了空间分辨率效应下外部区域的诊断缩放,进一步证明了其对小 L+ 的适用性,但对较大 L+ 的结果并不一致。这项研究的结果和数据库可能对湍流模型的开发和验证具有特殊意义,特别是在航空应用方面。
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来源期刊
Experimental Thermal and Fluid Science
Experimental Thermal and Fluid Science 工程技术-工程:机械
CiteScore
6.70
自引率
3.10%
发文量
159
审稿时长
34 days
期刊介绍: Experimental Thermal and Fluid Science provides a forum for research emphasizing experimental work that enhances fundamental understanding of heat transfer, thermodynamics, and fluid mechanics. In addition to the principal areas of research, the journal covers research results in related fields, including combined heat and mass transfer, flows with phase transition, micro- and nano-scale systems, multiphase flow, combustion, radiative transfer, porous media, cryogenics, turbulence, and novel experimental techniques.
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