Serrated slat cusp for high-lift device noise reduction

Jawahar, Hasan Kamliya; Ali, Syamir Alihan Showkat; Azarpeyvand, Mahdi

doi:10.1063/5.0035178

Cited by 15 publications

(5 citation statements)

References 45 publications

(31 reference statements)

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“…[6][7][8] Equally important, the turbulent inflow has a profound impact on turbulence interaction noise; specifically, an increase in turbulence length scale and turbulence intensity results in increased noise spectra levels. 9,10 Reduction of aerodynamically generated noise is proven to be effective through the means of passive flow control, be that through the use of serrations [11][12][13][14][15][16][17] or porous materials. [18][19][20][21][22][23][24] Serrations have been the subject of many studies for the reduction of turbulence interaction noise due to their ease of implementation; 16,[25][26][27][28] however, they require a fundamental change to the design of the airfoil geometry at the leading edge.…”

Section: Introductionmentioning

confidence: 99%

The role of porous structure on airfoil turbulence interaction noise reduction

Bowen,

Celik,

Westin

et al. 2024

Physics of Fluids

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Experiments are performed to investigate the effect of porous treatment structure used at the leading edge on the aerodynamic and aeroacoustic characteristics of a National Advisory Committee for Aeronautics (NACA) 0012 airfoil. Three different triply periodic minimal surface porous structures of constant porosity are studied to explore their effect on the flow field and the relationship between airfoil response and far-field noise. The results show that the ratio between the porous structure pore size and the length scale of the turbulent flow plays an important role in the noise reduction capability of a porous leading edge. Changes to the turbulent flow properties in the vicinity of the airfoil are assessed to characterize the contributing physical behavior responsible for far-field noise manipulation. Velocity field analysis in front of the leading edge demonstrates a pronounced difference among porous structures. Furthermore, close to the airfoil surface and off from the stagnation line, all porous leading edges demonstrate a marked reduction in the low-frequency content of the velocity fluctuations. These results demonstrate the importance of the airfoil leading edge region and not just the stagnation line. The strong link evident in pressure–velocity coherence analysis of the solid airfoil is broken by the introduction of the porous leading edge. Furthermore, the porous leading edges reduce the near-field to far-field pressure coherence in both magnitude and frequency range.

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Section: Introductionmentioning

confidence: 99%

The role of porous structure on airfoil turbulence interaction noise reduction

Bowen,

Celik,

Westin

et al. 2024

Physics of Fluids

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“…The experimental studies were primarily conducted in wind tunnels with size limitations, where the transition from laminar flow regime to turbulent flow regime is unlikely to occur due to the size of the test models. In order to achieve a turbulent flow over the airfoil, or at least over the trailing edge, and to mimic the conditions at high Reynolds number flow that the actual wings experience, a tripping tape is utilized to force an early (forced) transition to the turbulent regime over the airfoils in experiments [36][37][38][39][40]. Despite its utilization in almost all experiments, the number of investigations addressing the effect on mean quantities is limited [41][42][43] and frequency dependent effect does not exist.…”

Section: Introductionmentioning

confidence: 99%

Experimental investigation on the unsteady surface pressure fluctuation patterns over an airfoil

2022

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This article presents a comprehensive mapping of wall pressure fluctuations over an airfoil under three different inflow conditions to shed light on some basic assumptions taken granted for the recent aeroacoustic and aerodynamics experimental studies and in the noise prediction models. Unsteady and steady pressure measurements were performed over a heavily instrumented airfoil which was exposed to smooth inflow, grid generated turbulent inflow, and a smooth inflow with a tripping tape over the airfoil to explore the unsteady response of the airfoil for a broad range of angles of attack, 0◦ {less than or equal to} ᵯC; {less than or equal to} 20◦. The results are presented in terms of non-dimensional pressure coefficient, root mean square non-dimensional pressure coefficient, frequency-energy content pattern map at isolated frequencies for the entire airfoil,and spectra of frequency-energy content at selected transducer locations. The results show that the unsteady airfoil response patterns for the tripped boundary layer and turbulence ingestion cases show a dramatic difference compared to the airfoil response patterns of the smooth inflow conditions. The response patterns differ across angles of attack, frequency, and between both sides of the airfoil. The results suggest a three region pattern for smooth inflow case, a two region pattern for tripped boundary layer case, and a two region pattern for the turbulence ingestion case. Moreover, the results indicate that the presence of tripping may provide a flow with necessary statistical characteristics for the experimental rigs representing the full-scale application; however, it may misrepresent the frequency-dependent nature of the boundary layer.

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“…Therefore, various bionic serrated devices had been studied by simulation or experimental methods. 33,34 Jawahar et al 35 found that the slat serrations made a reduction of up to 5 dB in the overall energy level, and the acoustic mechanism was analyzed by higher-order spectral analysis and wavelet analysis. The sawteeth were effective in terms of the suppression of scattering waves.…”

Section: Introductionmentioning

confidence: 99%

Wavelet analysis of the coherent structures in airfoil leading-edge separation control by bionic coverts

Gong

Fan

et al. 2022

Proceedings of the Institution of Mechanical Engineers, Part C:

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We experimentally investigate leading-edge separation control effect by bionic coverts with various materials and sawteeth shapes in wind tunnel tests. The artificial flexible coverts, bio-inspired by bird covert feathers on upper wings, are hinged at the trailing-edge of a NACA 0018 airfoil at a constant high angle-of-attack of 15°. The chord-based Reynolds number is 1.0 × 105 in the generic range of bird flight in nature and low-speed fixed-wing unmanned aerial vehicles. The velocity profiles in the wake flow are measured by multi-channel hot-wire anemometer. By comparing the mean velocity profiles and root-mean-square velocities, we find the trailing-edge coverts reduced the thickness of the shear layers by 0.05 chord length. The turbulence intensity of the trailing- and leading-edge shear layers are reduced 34% and 5%, respectively. Further wavelet analysis reveals that the large sizes of vortices are considerably suppressed in the time-frequency spectrum. Based on the hot-wire datasets, we develop a novel multi-dimensional genetic algorithm to analyze the featured ordered structures in the shear layers and quantitatively characterize the amplitude modulation between the large- and small-scale flow structures. As a result, we find that the coverts-generated perturbations induce an increase in the high-frequency ( f = 91.2 Hz) coherence between the leading- and trailing-edge shear layers from 40% to 70%, leading to a reduction of the flow separation bubble on the upper wing. The present work reveals that the artificial bionic coverts have leading-edge flow separation control effectiveness and shows the engineering potential for aircrafts and unmanned aerial vehicles.

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Serrated slat cusp for high-lift device noise reduction

Cited by 15 publications

References 45 publications

The role of porous structure on airfoil turbulence interaction noise reduction

The role of porous structure on airfoil turbulence interaction noise reduction

Experimental investigation on the unsteady surface pressure fluctuation patterns over an airfoil

Wavelet analysis of the coherent structures in airfoil leading-edge separation control by bionic coverts

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