Reynolds number effects on flow/acoustic mechanisms in spherical windscreens

Zheng, Zhongquan Charlie; Tan, B. K.

doi:10.1121/1.1527927

Cited by 15 publications

(5 citation statements)

References 9 publications

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“…In particular, flow across a transversely oscillating cylinder is modeled. The result is an effective representation of flow-structure and wave-structure interactions for many applications of flow and acoustic problems related to flow over bluff bodies, as well as for noise reduction analysis in measurement microphones [e.g., Zheng and Tan (2003)]. In fact, several research groups have concentrated on measurement of the near wake of an oscillating cylinder and the related vortex-structure interactions [e.g., Bishop and Hassan (1964), Griffin (1971), Ongoren and Rockwell (1988), Carberry et al (2001), Williamson and Roshko (1988), and Krishnamoorthy et al (2001)].…”

Section: Introductionmentioning

confidence: 99%

Frequency effects on lift and drag for flow past an oscillating cylinder

Zheng

Zhang

2008

Journal of Fluids and Structures

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Section: Introductionmentioning

confidence: 99%

Frequency effects on lift and drag for flow past an oscillating cylinder

Zheng

Zhang

2008

Journal of Fluids and Structures

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“…3,4 That model was restricted to flow turbulence with scales much larger than the sphere diameter. The mean flow across the sphere could thus be considered steady.…”

Section: Introductionmentioning

confidence: 99%

A computational study of the effect of windscreen shape and flow resistivity on turbulent wind noise reduction

Zheng

Wilson

2011

The Journal of the Acoustical Society of America

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In this paper, numerical simulations are used to study the turbulent wind noise reduction effect of microphone windscreens with varying shapes and flow resistivities. Typical windscreen shapes consisting of circular, elliptical, and rectangular cylinders are investigated. A turbulent environment is generated by placing a solid circular cylinder upstream of the microphone. An immersed-boundary method with a fifth-order weighted essentially non-oscillatory scheme is implemented to enhance the simulation accuracy for high-Reynolds number flow around the solid cylinder as well as at the interface between the open air and the porous material comprising the windscreen. The Navier-Stokes equations for incompressible flow are solved in the open air. For the flow inside the porous material, a modified form of the Zwikker-Kosten equation is solved. The results show that, on average, the circular and horizontal ellipse windscreens have similar overall wind noise reduction performance, while the horizontal ellipse windscreen with medium flow resistivity provides the most effective wind noise reduction among all the considered cases. The vertical ellipse windscreen with high flow resistivity, in particular, increases the wind noise because of increased self-generation of turbulence.

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“…Phelps (1938) calculated the pressure inside microphone windscreens by averaging the pressure fluctuations on the windscreen surface based on the assumption that the air flow is irrotational and the windscreen is a rigid sphere. Similarly, with the smooth rigid sphere model, Zheng and Tan (2003) investigated the Reynolds number effects on the wind noise reduction performance of spherical microphone windscreens. However, the real microphone windscreens are mostly made of porous materials and far from the smooth rigid sphere.…”

Section: Introductionmentioning

confidence: 99%

Spatial decorrelation of wind noise with porous microphone windscreens

Zhao¹,

Cheng

Qiu

et al. 2018

The Journal of the Acoustical Society of America

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This paper explores the wind noise reduction mechanism of porous microphone windscreens by investigating the spatial correlation of wind noise. First, the spatial structure of the wind noise signal is studied by simulating the magnitude squared coherence of the pressure measured with two microphones at various separation distances, and it is found that the coherence of the two signals decreases with the separation distance and the wind noise is spatially correlated only within a certain distance less than the turbulence wavelength. Then, the wind noise reduction of the porous microphone windscreen is investigated, and the porous windscreen is found to be the most effective in attenuating wind noise in a certain frequency range, where the windscreen diameter is approximately 2 to 4 times the turbulence wavelengths (2 < D/ξ < 4), regardless of the wind speed and windscreen diameter. The spatial coherence between the wind noise outside and inside a porous microphone windscreen is compared with that without the windscreen, and the coherence is found to decrease significantly when the windscreen diameter is approximately 2 to 4 times the turbulence wavelengths, corresponding to the most effective wind noise reduction frequency range of the windscreen. Experimental results with a fan are presented to support the simulations. It is concluded that the wind noise reduction mechanism of porous microphone windscreens is related to the spatial decorrelation effect on the wind noise signals provided by the porous material and structure.

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Reynolds number effects on flow/acoustic mechanisms in spherical windscreens

Cited by 15 publications

References 9 publications

Frequency effects on lift and drag for flow past an oscillating cylinder

Frequency effects on lift and drag for flow past an oscillating cylinder

A computational study of the effect of windscreen shape and flow resistivity on turbulent wind noise reduction

Spatial decorrelation of wind noise with porous microphone windscreens

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