圆柱气动声学:截面形状对展向相干长度影响的实验研究

IF 1 3区 物理与天体物理 Q4 ACOUSTICS Acta Acustica Pub Date : 2023-01-01 DOI:10.1051/aacus/2022061
F. Margnat, Wagner J. Gonçalves da Silva Pinto, C. Noûs
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引用次数: 2

摘要

本文为不同截面圆柱体上的流动提供了新的数据和跨向相干长度的回顾:直径为d的圆形和截面纵横比(宽度(b)与高度(d)的比值AR = b/d)为1、2和3的矩形。在目前的测量中,车身的长度和展向长度都是固定的70d,并且雷诺数(基于d)范围为6000 - 27000。两点数据由两个热线探头获得,一个固定在对称平面上,另一个在相应的展向轴上移动。它们在交叉平面上的位置是由单个探头对平均流量的初步测量推断出来的,允许在不同的几何形状之间进行公平的比较,并引入相干长度值的不确定性条。在所有测试区,基于速度和基于压力的相干性实验数据之间存在非常好的一致性。重新审视相干长度定义,并选择气动声学一致的积分长度定义,允许将文献数据公平地合成为单个图表和经验函数。相干衰减模型的定义(例如高斯或拉普拉斯)也进行了调整,使相干长度和相干积分相等。这项关于相干性数据及其跨期整合的初步工作使透明的回归和模型选择成为可能。一般来说,高斯模型与升力峰有关,而相干性在谐波处表现出拉普拉斯衰减。平均而言,在斯特劳哈尔数峰值时,圆形和方形圆柱体的相干长度为5d,而矩形截面的相干长度约为15d。得出的结论是,后一种几何形状的流动在音调频率上仍然是二维动力学。这些值在测试的雷诺数范围内几乎保持不变。谐波处的相干长度值被广泛记录。横向相干长度也作为声效率的一个组成部分进行了讨论。
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Cylinder aeroacoustics: experimental study of the influence of cross-section shape on spanwise coherence length
New data and review of the spanwise coherence length is provided for flows over cylinders of different cross-sections: circular of diameter d, and rectangular of sectional aspect ratios (breadth (b) to height (d) ratio AR = b/d) of 1, 2 and 3. In the present measurements, the body has both d and spanwise length of 70d fixed, and the Reynolds number (based on d) range 6000–27,000 is covered. Two-point data are obtained from two hot-wire probes, one fixed in the symmetry plane and the other moving on the corresponding spanwise axis. Their position in a cross plane are deduced from preliminary measurement of the mean flow with a single probe, allowing fair comparisons between the different geometries and the introduction of uncertainty bars on coherence length values. At all tested regimes, a very good agreement is noticed between velocity-based and pressure-based coherence experimental data. Coherence length definitions are revisited, and the aeroacoustically consistent, integral length definition is selected, allowing fair synthesis of literature data into a single chart and empirical functions. Definitions for coherence decay models (e.g. Gaussian or Laplacian) are also adapted so that coherence length and coherence integral shall be equivalent. This preliminary work on coherence data and its spanwise integration enables transparent regressions and model selection. Generally, the Gaussian model is relevant for the lift peak, while the coherence exhibits a Laplacian decay at harmonics. On average, at peak Strouhal number, the coherence length for the circular and square cylinders is of 5d while it is of the order of 15d for the rectangular sections. It is concluded that the flow over those latter geometries is still a two-dimensional dynamics at the tone frequency. These values are almost preserved over the tested Reynolds number range. Coherence length value at harmonics is extensively documented. Spanwise coherence length is also discussed as an ingredient of acoustic efficiency.
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来源期刊
Acta Acustica
Acta Acustica ACOUSTICS-
CiteScore
2.80
自引率
21.40%
发文量
0
审稿时长
12 weeks
期刊介绍: Acta Acustica, the Journal of the European Acoustics Association (EAA). After the publication of its Journal Acta Acustica from 1993 to 1995, the EAA published Acta Acustica united with Acustica from 1996 to 2019. From 2020, the EAA decided to publish a journal in full Open Access. See Article Processing charges. Acta Acustica reports on original scientific research in acoustics and on engineering applications. The journal considers review papers, scientific papers, technical and applied papers, short communications, letters to the editor. From time to time, special issues and review articles are also published. For book reviews or doctoral thesis abstracts, please contact the Editor in Chief.
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