An Integrated Study of Laminar Separation Bubble Effect on Tonal Noise Generation in Transitional Airfoils

Yakhina, Gyuzel; Roger, Michel; Kholodov, Pavel; Nguyen, Lap; Golubev, Vladimir V.

doi:10.2514/6.2016-3022

Cited by 11 publications

(7 citation statements)

References 13 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Nevertheless as long as the mean pressure coefficient is at least reasonably reproduced in the aft part of the aerofoil, the trailing-edge noise sources are comparable. For these reasons, the mean measured pressure coefficient for the SD7003 aerofoil has been compared with that predicted by two-dimensional Reynolds-Averaged Navier-Stokes (RANS) numerical simulations [25], following the methodology proposed in [29]. In particular the computational domain includes the nozzle.…”

Section: Aerofoil Installationmentioning

confidence: 99%

“…It is aimed at completing the knowledge about tonal trailing-edge noise with experimental, analytical, and numerical investigations. The experimental study and the analytical modeling have been carried out at ECL [24,25] and the numerical simulations performed at ERAU [26][27][28]. Two aerofoils have been selected, namely the symmetric NACA-0012 aerofoil and a slightly cambered SD7003 aerofoil.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Experimental and Analytical Investigation of the Tonal Trailing-Edge Noise Radiated by Low Reynolds Number Aerofoils

et al. 2020

Self Cite

View full text Add to dashboard Cite

An experimental and analytical study of the tonal trailing-edge noise of a symmetric NACA-0012 aerofoil and of a cambered SD7003 aerofoil has been achieved. It provides a complete experimental database for both aerofoils and improves the understanding of the underlying mechanisms. The analysis stresses the high sensitivity of the tonal noise phenomenon to the flow velocity and the angle of attack. Several regimes of the noise emission are observed depending on the aforementioned parameters. The contributions of the pressure and the suction sides are found to vary with the flow parameters too. A special attention has been paid to the role of the separation bubble in the tonal noise generation. Hot-wire measurements and flow visualization prove that the separation bubble is a necessary condition for the tonal noise production. Moreover, the bubble must be located close enough to the trailing edge. Several tests with small-scale upstream turbulence confirm the existence of the feedback loop. Analytical predictions with a classical trailing-edge noise model show a good agreement with the experimental data; they confirm the cause-to-effect relationship between the wall-pressure fluctuations and the radiated sound. Finally, previously reported works on fans and propellers are shortly re-addressed to show that the tonal noise associated with laminar-boundary-layer instabilities can take place in rotating blade technology.

show abstract

Section: Aerofoil Installationmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Experimental and Analytical Investigation of the Tonal Trailing-Edge Noise Radiated by Low Reynolds Number Aerofoils

et al. 2020

Self Cite

View full text Add to dashboard Cite

show abstract

“…1,5 Such a tonal noise has been observed within the context of several different applications, including UAVs and low-speed fans. It has been intensively studied on the symmetric NACA0012 airfoil at low to transitional Reynolds numbers since the 1970s 11 and has received renewed interest with improved measurement techniques [12][13][14][15] and with direct numerical simulations (DNS). [16][17][18][19] Yet no consensus has been reached on the aeroacoustic/hydrodynamic feedback mechanisms 20 which may involve upstream propagating acoustic waves and hydrodynamic influence of recirculation bubbles on the airfoil 14 and wake turbulent structures.…”

Section: Introductionmentioning

confidence: 99%

Modal analysis of the laminar boundary layer instability and tonal noise of an airfoil at Reynolds number 150,000

Sanjosé

Towne

Jaiswal

et al. 2018

International Journal of Aeroacoustics

View full text Add to dashboard Cite

A direct numerical simulation of the flow field around a controlled-diffusion airfoil within an anechoic wind-tunnel at 5 • incidence and a high Reynolds number of 1.5 × 10 5 is performed for the first time using a Lattice Boltzmann Method. The simulation compares favorably with experimental measurements of wall-pressure, wake statistics, and far-field sound. The simulation noticeably captures experimentally observed high-amplitude acoustic tones that rise above a broadband hump. Both noise components are related to a breathing of a recirculation bubble formed around 65-70% of the chord, and to Kelvin-Helmholtz instabilities in the separated shear layer that yield rollers that break down into turbulent vortices whose diffraction at the trailing edge produces a strong dipole acoustic field. A wavelet analysis of the wall-pressure signals combined with some flow visualization has shown that the flow statistics are dominated by intense events caused by intermittent, large and intense bursting rollers. Several modal analyses of these events are performed on both the wall pressure fluctuations and the span averaged flow field in order to analyse the boundary layer instability which triggers the typical sharp tones over a broadband hump in airfoil noise. A suction side Kelvin-Helmholtz instability is observed to be coupled with a pressure side vortex shedding induced by the sudden transition to turbulence and the blunt trailing edge.

show abstract

“…Moreover, Liu and Chen [33] have illustrated that a porous permeable structure located in the middle of the model will generate a cavity tonal component under symmetrical flow conditions, which can also explain the better noise reduction in L00M00N06 at a zero angle of attack. On the other hand, Yakhina et al [24] have revealed that the laminar separation bubble starts earlier on the suction side and moves downstream on the pressure side with an increasing angle of attack. Therefore, the airflow passing through pores that are distributed in the upstream subregion will have an earlier impact on the boundary layer regime and then suppress laminar instability tonal noise, which can explain the better performance of L06M00N00 at α = 10 • .…”

Section: Effect Of the Pore Positionmentioning

confidence: 99%

“…It is agreed that a laminar separation area on either the pressure side or the suction side of the airfoil trailing edge is a necessary condition for the generation of strong tonal noise resulting from instability [19][20][21]. Moreover, it is found that the state of the boundary layer flow (laminar or turbulent) close to the airfoil trailing edge is significantly dependent on both model parameters (such as chord length and airfoil camber) and flow parameters (free-stream velocity and angle of attack) [22][23][24]. Therefore, the aforementioned sensitivity of the airfoil tonal noise stems from the complex nature of the laminar separation in the trailing edge boundary layer.…”

Section: Experimental Validation Of the Baseline Airfoilmentioning

confidence: 99%

Experimental Investigation of Airfoil Instability Tonal Noise Reduction Using Structured Porous Trailing Edges

Wang,

Zuo,

Guo

et al. 2024

Applied Sciences

View full text Add to dashboard Cite

Reducing the tonal noise from airfoil instabilities has attracted significant interest from the aeronautical community in the past few years. The aim of this paper is to investigate the effect of structured porous trailing edges on the tonal noise reduction performance of a symmetrical NACA 0012 airfoil. Detailed parametric testing was performed in an open-jet wind tunnel between the baseline solid trailing edge and seventeen structured porous trailing edges with different sub-millimeter-scale pores. The experimental results demonstrate that structured porous trailing edges can reduce the noticeable tonal noise of the symmetrical NACA 0012 airfoil. Moreover, the design parameters for the structured porous edges have slightly different impacts on the tonal noise reduction performance between a zero angle of attack (α = 0°) and a non-zero angle of attack (α = 10°): better airfoil tonal noise reduction is due to the porous parameters of small pore coverage, small-to-moderate chordwise spacing, and moderate spanwise spacing at α = 0°. On the other hand, the optimal combination of the structured porous edge at α = 10° is the configuration with larger pore coverage, smaller chordwise spacing, and spanwise spacing.

show abstract

An Integrated Study of Laminar Separation Bubble Effect on Tonal Noise Generation in Transitional Airfoils

Cited by 11 publications

References 13 publications

Experimental and Analytical Investigation of the Tonal Trailing-Edge Noise Radiated by Low Reynolds Number Aerofoils

Experimental and Analytical Investigation of the Tonal Trailing-Edge Noise Radiated by Low Reynolds Number Aerofoils

Modal analysis of the laminar boundary layer instability and tonal noise of an airfoil at Reynolds number 150,000

Experimental Investigation of Airfoil Instability Tonal Noise Reduction Using Structured Porous Trailing Edges

Contact Info

Product

Resources

About