Sound source and pseudo-sound in the near field of a circular cylinder in subsonic conditions

Li, Shuai; Rival, David E.; Wu, Xiaohua

doi:10.1017/jfm.2021.404

Cited by 27 publications

(16 citation statements)

References 51 publications

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“…The findings are consistent with the study conducted by Li et al. (2021), which emphasised that the shoulder of the cylinder plays a more significant role in sound emission than the oscillating near wake just behind the cylinder.…”

Section: Wake Flow Fieldsupporting

confidence: 93%

“…This indicates that the acoustic waves resulting from surface pressure fluctuations are more likely to radiate to the far field compared with those originating from the hydrodynamic field. The findings are consistent with the study conducted by Li et al (2021), which emphasised that the shoulder of the cylinder plays a more significant role in sound emission than the oscillating near wake just behind the cylinder.…”

Section: Velocity-pressure Coherencesupporting

confidence: 92%

“…This trend highlights the significant contribution of surface pressure fluctuations, induced by vortex shedding in the preseparation and postseparation regions, to the generation of tonal noise (Maryami et al 2023c). Previous studies have reported that surface pressure fluctuations near the flow separation point act as sound sources (Oguma et al 2013) and strongly scatter sound in a region approximately from θ = 25 • to 155 • (Li, Rival & Wu 2021).…”

Section: Near-field Pressure To Far-field Noise Coherencementioning

confidence: 72%

“…Previous studies have reported that surface pressure fluctuations near the flow separation point act as sound sources (Oguma et al. 2013) and strongly scatter sound in a region approximately from to (Li, Rival & Wu 2021).

Figure 18.Coherence between the near-field pressure and far-field noise, , in terms of for the pressure taps located at , , , and .…”

Section: Wake Flow Fieldmentioning

confidence: 99%

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Flow and aerodynamic noise control of a circular cylinder by local blowing

Maryami,

Arcondoulis,

Liu

2024

J. Fluid Mech.

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In this experimental study, the impact of symmetric local blowing on suppressing the vortex-induced noise of a circular cylinder was investigated. A highly instrumented cylinder with pressure taps and a series of blowing chambers was used to inject air along the span (seven times the cylinder diameter) at circumferential angles $\theta _{b}={\pm }41^{\circ }$ , ${\pm }90^{\circ }$ and ${\pm }131^{\circ }$ corresponding to the boundary layer, shear layers on the cylinder and separated shear layers, respectively. The investigation aimed to understand the noise reduction mechanism of local blowing by conducting near-field pressure and far-field noise measurements in synchronisation with flow field velocity measurements. Near-field pressure was measured around the circumference of the cylinder using a remote-sensing technique and planar particle image velocimetry was implemented to measure the velocity of the wake flow field at a diameter-based Reynolds number of $Re=7\times 10^{4}$ . The results revealed that the interaction of the rolling up separated shear layers, under the influence of high-momentum fluid travelling from the free stream to the wake, induced significant vertical flow movement in the vortex-formation region. This movement led to strong alternating surface pressure fluctuations at the cylinder's shoulders, contributing to the scattering of noise. It was demonstrated that local blowing delayed vortex shedding for all cases, except at $\theta _{b}={\pm }90^{\circ }$ , which elongated the shear layers and pushed the high-momentum transfer area farther downstream. The application of local blowing at $\theta _{b}={\pm }41^{\circ }$ was particularly effective in increasing the vortex formation size due to reduced entrainment of fluid-bearing vorticity.

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Section: Wake Flow Fieldsupporting

confidence: 93%

Section: Velocity-pressure Coherencesupporting

confidence: 92%

Section: Near-field Pressure To Far-field Noise Coherencementioning

confidence: 72%

Figure 18.Coherence between the near-field pressure and far-field noise, , in terms of for the pressure taps located at , , , and .…”

Section: Wake Flow Fieldmentioning

confidence: 99%

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Flow and aerodynamic noise control of a circular cylinder by local blowing

Maryami,

Arcondoulis,

Liu

2024

J. Fluid Mech.

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“…The method has been successfully applied and validated in several previous papers including configurations significantly different from the one analyzed therein (see e.g. [29][30][31][32]).…”

mentioning

confidence: 99%

On the influence of the nozzle exhaust initial conditions on the near field acoustic pressure

2022

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In this paper, the acoustic pressure generated in the near field of a single stream cold jet is investigated. The analysis is focused on the effect of the initial conditions at the nozzle exit parametrized by considering two different turbulence levels and two different boundary layer thicknesses. The study has been performed by processing a numerical database obtained by large-eddy simulations (LES) of a jet flow at M = 0.9 and Re = 105. Pressure time series are obtained from pointwise virtual probes located in several radial and axial positions in the jet near-field. The acoustic pressure is extracted by the application of a consolidated wavelet-based procedure and the achieved acoustic signals are analyzed in terms of global quantities as well as by computing wavelet-reconstructed Fourier spectra. The results show that both the boundary-layer thickness and the turbulence level significantly affect the acoustic pressure in terms of its intensity and directivity whereas the distribution of energy in the frequency domain depends appreciably, only on the boundary-layer thickness.

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