Sound radiated from low Mach number turbulent boundary layer flows（Turbulent boundary layer on a smooth plate and over a small forward facing step）

IF 0.7 Q4 MECHANICS

Journal of Fluid Science and Technology Pub Date : 2021-01-01 DOI:10.1299/JFST.2021JFST0010

Shiko Moriyama, Yohei Inoue, H. Maekawa

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引用次数: 0

Abstract

High-resolution numerical simulation has been performed to study aeroacoustic noise radiated from a turbulent boundary layer at freestream Mach number Ma = 0.3, which develops on a smooth flat plate and over a small forward-facing step. Sound waves radiated from the turbulent boundary layer on the flat plate are dominant in a very-low-frequency band and have characteristics of a linear sound source. The sound waves are observed in the far-field from the boundary propagate outside of the flow region where small hydrodynamic pressure fluctuations with a significant long-wavelength appear. The instantaneous hydrodynamic pressure fields that gradually develop or decay while moving downstream with the turbulent boundary layer are associated with the evolution of various vortical structures. The characteristics of the sound wave being a linear sound source and dominant in a very-low-frequency band are similar to those of the real high-speed train. The sound waves generated from the turbulent boundary layer over the forward-facing step with a height (SH) of SH/y ≅ 62 are significantly larger in a full frequency band than those radiated from the turbulent boundary layer on the flat plate. Numerical results of the turbulent boundary layer over the forward-facing step with a height of SH/y ≅ 30 show that the sound waves are dominant in the low-frequency band, and also step-specific sound waves are generated in the high-frequency band. Further, even if the step height is SH/y ≅ 7.5, the sound waves unique to the small step are generated in the high-frequency band.

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低马赫数湍流边界层(平滑板上的湍流边界层和向前小台阶上的湍流边界层)辐射声

采用高分辨率数值模拟方法，研究了自由流马赫数Ma = 0.3时湍流边界层辐射的气动噪声，该噪声在光滑的平板上和向前的小台阶上发展。平板上湍流边界层辐射的声波在极低频段占主导地位，具有线性声源的特征。在边界远场观测到的声波在流区外传播，在流区外出现明显的长波长小的动水压力波动。瞬时水动压力场随湍流边界层向下游移动而逐渐发展或衰减，与各种涡旋结构的演化有关。声波作为线性声源，在极低频波段占优势，其特性与真实高速列车相似。在整个频带内，前台阶上方湍流边界层所产生的声波高度(SH)为SH/y × 62，明显大于平板上湍流边界层所辐射的声波。对高度为SH/y = 30的前台阶湍流边界层的数值计算结果表明，声波在低频波段占优势，在高频波段也会产生台阶特有的声波。此外，即使阶跃高度为SH/y = 7.5，也会在高频波段产生小阶跃特有的声波。

本文章由计算机程序翻译，如有差异，请以英文原文为准。

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来源期刊

Journal of Fluid Science and Technology MECHANICS-

CiteScore

1.00

自引率

12.50%

发文量

期刊介绍： Journal of Fluid Science and Technology (JFST) is an international journal published by the Fluids Engineering Division in the Japan Society of Mechanical Engineers (JSME). JSME had been publishing Bulletin of the JSME (1958-1986) and JSME International Journal (1987-2006) by the continuous volume numbers. Considering the recent circumstances of the academic journals in the field of mechanical engineering, JSME reorganized the journal editorial system. Namely, JSME discontinued former International Journals and projected new publications from the divisions belonging to JSME. The Fluids Engineering Division acted quickly among all divisions and launched the premiere issue of JFST in January 2006. JFST aims at contributing to the development of fluid engineering by publishing superior papers of the scientific and technological studies in this field. The editorial committee will make all efforts for promoting strictly fair and speedy review for submitted articles. All JFST papers will be available for free at the website of J-STAGE (http://www.i-product.biz/jsme/eng/), which is hosted by Japan Science and Technology Agency (JST). Thus papers can be accessed worldwide by lead scientists and engineers. In addition, authors can express their results variedly by high-quality color drawings and pictures. JFST invites the submission of original papers on wide variety of fields related to fluid mechanics and fluid engineering. The topics to be treated should be corresponding to the following keywords of the Fluids Engineering Division of the JSME. Basic keywords include: turbulent flow; multiphase flow; non-Newtonian fluids; functional fluids; quantum and molecular dynamics; wave; acoustics; vibration; free surface flows; cavitation; fluid machinery; computational fluid dynamics (CFD); experimental fluid dynamics (EFD); Bio-fluid.