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

Moriyama, Shiko; Inoue, Yoshio; Maekawa, Hiroshi

doi:10.1299/jfst.2021jfst0010

Cited by 2 publications

(1 citation statement)

References 17 publications

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“…In addition, the large scale vortices occur in separated shear layer for the ratio of large step height to boundary layer thickness such as H/δ and the low frequency sound corresponds to it. Moriyama et al (2021) carry out direct numerical simulation for turbulent boundary layer developed on a small forward facing step and they investigate aerodynamic sound radiates from it. As a result, step-specific sound is observed in high frequency range under the different conditions of H/δ.…”

Section: Introductionmentioning

confidence: 99%

Experimental study on aerodynamic sound generated from flow around a forward facing step

SHIRASU¹,

Suzuki

Kato

2023

JFST

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Aerodynamic noise in high frequency band related in the flows around A-pillar is easily propagated to the cabin of the automobile. Understanding of the characteristics of the aerodynamic noise is needed to reduce the cabin noise. Moreover, understanding of the separated shear layer which is strongly affected by the condition of the step hight H to the boundary layer thickness δ is needed. In this study, far field sound and correlation measurement of flow velocity are measured to investigate the characteristics of aerodynamic noise and the relationship between H/δ and turbulence length scale L as eddy scale for the forward facing step. As a result, multiple gradual peaks in more than 1 kHz are observed in the aerodynamic sound spectra. Furthermore, it is found that turbulence length scale L increases for increasing of H/δ and turbulence length scale to step height for H/δ = 2.0 is almost equal to that for H/δ = 3.0. Then, it is clear that spectral peaks are strongly affected by step height. And it is confirmed that H/δ = 2.0 and 3.0 are equal in turbulence length scale to the step height.

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Section: Introductionmentioning

confidence: 99%

Experimental study on aerodynamic sound generated from flow around a forward facing step

SHIRASU¹,

Suzuki

Kato

2023

JFST

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角柱近傍を移動する渦対による音波発生について

Kanuma¹,

Inoue²,

Maekawa³

2023

Transactions of the JSME (In Japanese)

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The sound generated by a vortex pair moving close to a rectangular cylinder is studied by high-resolution simulations of the two-dimensional unsteady compressible Navier-Stokes equations at Mach numbers ranging from 0.05 to 0.3. In this study, the Mach number Ma is defined by Ma=Vt /c0, where Vt is the translation velocity of the co-moving vortex pair and c0 denotes the speed of sound. The directly computed far-field sound is compared to the prediction of the acoustic analogy proposed by and . The prediction is in excellent agreement with the simulation, where the two-dimensional form of Curle's modified solution is adopted for an accurate calculation of the sound waves with a phase difference between various vortices around the cylinder. It could be confirmed that the scaling law in two dimensions holds in this simulation. In this study, the sound generation due to the dipole and quadrupole fields is investigated by calculating the two terms in Curle's analogy. Examining the surface distribution of dipoles on the cylinder indicates that the force exerted on the fluid by the solid boundaries of the side/upper wall of the rectangular cylinder generates the sound when the co-translating vortices approach /pass the rectangular cylinder, which is the sound due to dipoles corresponding to the directivity of the sound in the polar diagrams. The area distribution of quadrupoles which is the second time derivative of the area integral of Lighthill's stress tensor indicates that the sound is emitted from a vortex generated at the corner of the rectangular cylinder when the vortex pair approaches the cylinder and where the interaction between many vortices around the cylinder and the co-translating vortices generates the sound when the co-translating vortices pass the cylinder.

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

Cited by 2 publications

References 17 publications

Experimental study on aerodynamic sound generated from flow around a forward facing step

Experimental study on aerodynamic sound generated from flow around a forward facing step

角柱近傍を移動する渦対による音波発生について

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