On the study of wavy leading-edge vanes to achieve low fan interaction noise

Tong, Fan; Qiao, Weiyang; Xu, Kun; Wang, Liangfeng; Chen, Weijie; Wang, Xunnian

doi:10.1016/j.jsv.2018.01.017

Cited by 40 publications

(12 citation statements)

References 26 publications

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“…It was demonstrated that the source magnitude is significantly reduced in the WLE's hill region (see figure 1) at all frequencies, whereas the root and peak regions show a similar level of source magnitude to that of SLE. The reduced source magnitude at the hill region has also been observed by Clair et al (2013) and Tong et al (2018). Additionally, an increasing level of destructive phase interference in the source signals along the WLE (compared to SLE) appeared in the early study of Kim et al (2016).…”

Section: Introductionmentioning

confidence: 68%

“…Here, the reduction of the noise is measured relative to the straight leading edge (SLE) case. The noise reduction effect of WLEs has been demonstrated through mathematical (Lyu & Azarpeyvand 2017;Mathews & Peake 2018;Ayton & Kim 2018), experimental (Hansen et al 2012;Narayanan et al 2015;Chong et al 2015;Roger & Moreau 2016;Chaitanya et al 2017;Biedermann et al 2017;Juknevicius & Chong 2018) and computational studies (Lau et al 2013;Clair et al 2013;Kim et al 2016;Agrawal & Sharma 2016;Tong et al 2018). The previous studies reported that significant noise reduction (typically more than 3dB) was available for Strouhal numbers St LE 0.5 (normalised by the peak-to-root distance of the WLE and the free-stream velocity).…”

Section: Introductionmentioning

confidence: 98%

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On the universal trends in the noise reduction due to wavy leading edges in aerofoil–vortex interaction

Turner

Kim

2019

J. Fluid Mech.

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Existing studies suggest that wavy leading edges (WLEs) offer substantial reduction of broadband noise generated by an aerofoil undergoing upstream vortical disturbances. In this context, there are two universal trends in the frequency spectra of the noise reduction which have been observed and reported to date: (i) no significant reduction at low frequencies followed by (ii) a rapid growth of the noise reduction that persists in the medium-to-high frequency range. These trends are known to be insensitive to the aerofoil type and flow condition used. This paper aims to provide comprehensive understandings as to how these universal trends are formed and what the major drivers are. The current work is based on very-high-resolution numerical simulations of a semi-infinite flat-plate aerofoil impinged by a prescribed divergence-free vortex in an inviscid base flow at zero incidence angle, continued from recent work by the authors (Turner & Kim, J. Fluid Mech., vol. 811, 2017, pp. 582–611). One of the most significant findings in the current work is that the noise source distribution on the aerofoil surface becomes entirely two-dimensional (highly non-uniform in the spanwise direction as well as streamwise) at high frequencies when the WLE is involved. Also, the sources downstream of the LE make crucial contributions to creating the universal trends across all frequencies. These findings contradict the conventional LE-focused one-dimensional source analysis that has widely been accepted for all frequencies. The current study suggests that the universal trends in the noise-reduction spectra can be properly understood by taking the downstream source contributions into account, in terms of both magnitude and phase variations. After including the downstream sources, it is shown in this paper that the first universal trend is due to the conservation of total (surface integrated) source energy at low frequencies. The surface-integrated source magnitude that decreases faster with the WLE correlates very well with the noise-reduction spectrum at medium frequencies. In the meantime, the high-frequency noise reduction is driven almost entirely by destructive phase interference that increases rapidly and consistently with frequency, explaining the second universal trend.

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Section: Introductionmentioning

confidence: 68%

Section: Introductionmentioning

confidence: 98%

On the universal trends in the noise reduction due to wavy leading edges in aerofoil–vortex interaction

Turner

Kim

2019

J. Fluid Mech.

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“…Besides the experimental work, there are also some analytical and numerical investigations. These include serrated and wavy leading edges [19][20][21][22][23][24][25][26][27] as well as porous materials [28,29]. Another recent numerical study was performed on the potential noise reduction of a blade with a leading-edge modified with hooks [30].…”

Section: Introductionmentioning

confidence: 99%

Experimental Study of Airfoil Leading Edge Combs for Turbulence Interaction Noise Reduction

2020

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The interaction of a turbulent flow with the leading edge of a blade is a main noise source mechanism for fans and wind turbines. Motivated by the silent flight of owls, the present paper describes an experimental study performed to explore the noise-reducing effect of comb-like extensions, which are fixed to the leading edge of a low-speed airfoil. The measurements took place in an aeroacoustic wind tunnel using the microphone array technique, while the aerodynamic performance of the modified airfoils was captured simultaneously. It was found that the comb structures lead to a noise reduction at low frequencies, while the noise at high frequencies slightly increases. The most likely reasons for this frequency shift are that the teeth of the combs break up large incoming turbulent eddies into smaller ones or that they shift turbulent eddies away from the airfoil surface, thereby reducing pressure fluctuations acting on the airfoil. The aerodynamic performance does not change significantly.

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“…In the marine field, Gao [12] studied the effect of leading-edge protuberances on the rudder, and found that protuberances had drag reduction ability. In the mechanical field, Tong [13] applied leading-edge protuberances to the vanes of axial fans, and concluded that fan efficiency was improved and fan noise was reduced. For the wavy parameters of the leading edge, currently, only two parameters have been proposed, namely, wavelength (or wavenumber) and amplitude (shown in Figure 1a).…”

Section: Introductionmentioning

confidence: 99%

Aeroacoustic Optimization of the Bionic Leading Edge of a Typical Blade for Performance Improvement

Liu

Yang

et al. 2021

Machines

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New, innovative optimization approaches to improve turbomachine performance and reduce turbomachine noise are significant in engineering. In this paper, based on the bionic concept, a wave structure is used to shape the leading edge of the blade. Using an NACA0018 blade as the basic blade, a united parametric approach controlled by three parameters is proposed to configure the wavy leading edge. Then, a new optimization strategy boosting design efficiency is established to output the optimal design results. Finally, the corresponding performance and flow mechanism are analyzed. Taking into account the existence of the hub wall and the shroud wall from the closed impeller, a near-wall adjustment factor is added, the significance of which is herein demonstrated. An optimal bionic blade is successfully obtained by the optimization strategy, which can reduce the mean drag coefficient by about 6% and the overall sound pressure level by about 3 dB, in relative to the original blade. Mechanism analysis revealed that the wave structure can induce spanwise velocity at the leading edge and cause a further delay in flow separation in the downstream region, synchronously reducing drag and noise.

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On the study of wavy leading-edge vanes to achieve low fan interaction noise

Cited by 40 publications

References 26 publications

On the universal trends in the noise reduction due to wavy leading edges in aerofoil–vortex interaction

On the universal trends in the noise reduction due to wavy leading edges in aerofoil–vortex interaction

Experimental Study of Airfoil Leading Edge Combs for Turbulence Interaction Noise Reduction

Aeroacoustic Optimization of the Bionic Leading Edge of a Typical Blade for Performance Improvement

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