Airfoil Trailing Edge Noise Source Location for Low to Moderate Reynolds Number

Arcondoulis, Elias; Doolan, Con J.; Brooks, Laura; Zander, Anthony C.

doi:10.2514/6.2011-2785

Cited by 33 publications

(36 citation statements)

References 6 publications

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“…This study underlines the sensitivity of experimental results towards the laboratory environment and experimental conditions. In a recent review on the topic, Arcondoulis et al (2010) mentioned that, for instance, the free stream turbulence can be an important factor, promoting or delaying transition in the low-Reynolds-number regime. Arbey & Bataille (1983) investigated the case of a NACA 0012 aerofoil with models of different chord length at zero incidence.…”

Section: Early Observations and Scaling Rulesmentioning

confidence: 99%

“…The earliest reports date back to the work of Hersh & Hayden (1971), and the work is clearly not closed considering the very recent studies of Tam & Ju (2012) and Plogmann, Herrig & Würz (2013). Aerofoils operating in such conditions can be found in micro-wind turbines as well as in compressors, cooling fans and other rotating machinery (Wright 1976;Arcondoulis et al 2010). While self-noise generated by aerofoils at high Reynolds numbers in an undisturbed flow and in the absence of † Email address for correspondence: s.probsting@tudelft.nl separation is dominated by the interaction of the turbulent boundary layers with the trailing edge (Roger & Moreau 2010), tones produced at moderate Reynolds numbers are often associated with the growth and convection of unstable waves in the laminar boundary layer (Arbey & Bataille 1983).…”

Section: Introductionmentioning

confidence: 99%

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Experimental investigation of aerofoil tonal noise generation

2014

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The present study investigates the mechanisms associated with tonal noise emission from a NACA 0012 aerofoil at moderate incidence (0• and 4• angle of attack) and with Reynolds numbers ranging from 100 000 to 270 000. Simultaneous time-resolved particle image velocimetry (PIV) of the aeroacoustic source region near the trailing edge and acoustic measurements in the far field are performed in order to establish the correspondence between the flow structure and acoustic emissions. Results of these experiments are presented and analysed in view of past research for a number of selected cases. Characteristics of the acoustic emission and principal features of the average flow field agree with data presented in previous studies on the topic. Time-resolved analysis shows that downstream convecting vortical structures, resulting from growing shear layer instabilities, coherently pass the trailing edge at a frequency equal to that of the dominant tone. Therefore, the scattering of the vortical structures and their associated wall pressure fluctuations are identified as tone generating mechanisms for the cases investigated here. Moreover, wavelet analysis of the acoustic pressure and velocity signals near the trailing edge show a similar periodic amplitude modulation which is associated with multiple tonal peaks in the acoustic spectrum. Periodic amplitude modulation of the acoustic pressure and velocity fluctuations on the pressure side are also observed when transition is forced on the suction side, showing that pressure-side events alone can be the cause.

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Section: Early Observations and Scaling Rulesmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Experimental investigation of aerofoil tonal noise generation

2014

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“…at frequencies f n proportional to a power of the free-stream velocity u 0.85 ∞ . The dominant tone f n max (also denoted as the primary tone (Arcondoulis et al 2010)) followed this variation over a finite range of Reynolds numbers before a transition (or jump) to a different frequency (different index n) was observed. This particular structure of the spectrum with a primary tone f n max and multiple side tones f n (also denoted secondary tones) is called a ladder-type structure, where the primary tone f n max constitutes the rungs of the ladder.…”

Section: Introductionmentioning

confidence: 99%

“…It bears significance for a large number of applications, e.g. small-scale wind turbines, fans and -especially in recent years -unmanned aerial vehicles (Arcondoulis et al 2010). Compared to broadband noise, tonal components are particularly displeasing and unwanted.…”

Section: Introductionmentioning

confidence: 99%

Regimes of tonal noise on an airfoil at moderate Reynolds number

2015

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Tonal noise generated by airfoils at low to moderate Reynolds number is relevant for applications in, for example, small-scale wind turbines, fans and unmanned aerial vehicles. Coherent and convected vortical structures scattering at the trailing edge from the pressure or suction sides of the airfoil have been identified to be responsible for such tonal noise generation. Controversy remains on the respective significance of pressure-and suction-side events, along with their interaction for tonal noise generation. The present study surveys the regimes of tonal noise generation for low to moderate chord-based Reynolds number between Re c = 0.3 × 10 5 and 2.3 × 10 5 and effective angle of attack between 0 • and 6.3 • for the NACA 0012 airfoil profile. Extensive acoustic measurements with smooth surface and with transition to turbulence forced by boundary layer tripping are presented. Results show that, at non-zero angle of attack, tonal noise generation is dominated by suction-side events at low Reynolds number and by pressure-side events at high Reynolds number. At smaller angle of attack, interaction between events on the two sides becomes increasingly important. Particle image velocimetry measurements complete the information on the flow field structure in the source region around the trailing edge. The influences of both angle of attack and Reynolds number on tonal noise generation are explained by changes in the mean flow topology, namely the presence and location of reverse flow regions on the two sides. Data gathered from experimental and numerical studies in the literature are reviewed and interpreted in view of the different regimes.

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“…In the recent years, many authors have investigated the tonal noise generation mechanisms from aerofoils, in different conditions and for different geometries (Arcondoulis et al, 2011;Desquesnes et al, 2007;Jones et al, 2008;2010;Kurotaki et al, 2008). Many studies agree that T-S instability waves are established and that a feedback loop mechanisms is sustained, thus generating the tone.…”

Section: Introductionmentioning

confidence: 99%

Numerical Prediction of the Tonal Airborne Noise for a NACA 0012 Aerofoil at Moderate Reynolds Number Using a Transitional URANS Approach

Gennaro¹,

Kühnelt²,

Zanon³

2017

Archives of Acoustics

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Tonal airborne noise of aerofoils appears in a limited range of moderate Reynolds numbers and angles of attack. In these specific conditions, the aerofoil is characterised by a large region of laminar flow over the aerodynamic surface, typically resulting in two-dimensional laminar instabilities in the boundary layer, generating one or more acoustic tones. The numerical simulation of such phenomenon requires, beside an accurate prediction of the unsteady flow field, a proper modelling of the laminar to turbulent transition of the boundary layer, which generally imposes the use of highly CPU demanding approaches such as large eddy simulation (LES) or direct numerical simulation (DNS). This paper aims at presenting the results of numerical experiments for evaluating the capability of capturing the tonal airborne noise by using an advanced, yet low computationally demanding, unsteady Reynolds-averaged Navier-Stokes (URANS) turbulence model augmented with a transitional model to account for the laminar to turbulent transition. This approach, coupled with the Ffowcs Williams and Hawkings (FW-H) acoustic analogy, is adopted for predicting the far-field acoustic sound pressure of a NACA 0012 aerofoil with Reynolds number ranging from 0.39 · 10 6 to 1.09 · 10 6 . The results show a main tone located approximately at 1.6-1.8 kHz for a Reynolds number equal to 0.62 · 10 6 , increasing to 2.4 kHz at Reynolds number equal to 0.85 · 10 6 and 3.4 kHz at 1.09 · 10 6 , while no main tones are observed at 0.39 · 10 6 . The computed spectra confirm that the acoustic emission of the aerofoil is dominated by tonal structures and that the frequency of the main tone depends on the Reynolds number consistently with the ladder-like tonal structure suggested by Paterson et al. Moreover, in specific conditions, the acoustic spectra exhibit a multi-tonal structure visible in narrowband spectra, in line with the findings of Arbey and Bataille. The presented results demonstrate the capability of the numerical model of predicting the physics of the tonal airborne noise generation.

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Airfoil Trailing Edge Noise Source Location for Low to Moderate Reynolds Number

Cited by 33 publications

References 6 publications

Experimental investigation of aerofoil tonal noise generation

Experimental investigation of aerofoil tonal noise generation

Regimes of tonal noise on an airfoil at moderate Reynolds number

Numerical Prediction of the Tonal Airborne Noise for a NACA 0012 Aerofoil at Moderate Reynolds Number Using a Transitional URANS Approach

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