On the noise reduction of a porous trailing edge applied to an airfoil at lifting condition

Teruna, Christopher; Avallone, Francesco; Ragni, Daniele; Casalino, Damiano

doi:10.1063/5.0047512

Cited by 25 publications

(9 citation statements)

References 52 publications

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“…2018; Teruna et al. 2020, 2021). The cross-spectrum density (CSD) between two pressure signals at two locations is defined as The coherence refers to the normalized amplitude for the CSD, i.e.…”

Section: Resultsmentioning

confidence: 99%

“…It has been shown that the most vital noise sources are mainly located near the trailing edges. In order to study the detailed distribution of the noise sources on the airfoil and its influence on the far-field noise, we divide the airfoil surface, including the serrated surface, into many strips (Avallone et al 2018;Teruna et al 2020), as illustrated in figure 16. Here, we are mainly concerned with the influence of a fully developed area, and the surface with x/l > 0.5 is split into many spanwise strips.…”

Section: The Influence Of Serrations On Dipole Sourcesmentioning

confidence: 99%

“…St Beyond the discussion on the variation of the dipole source strength, we also explore the coherence between different strips (Avallone et al 2018;Teruna et al 2020Teruna et al , 2021. The cross-spectrum density (CSD) between two pressure signals at two locations is defined as…”

Section: Casesmentioning

confidence: 99%

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Noise reduction mechanisms for insert-type serrations of the NACA-0012 airfoil

Wan

et al. 2022

J. Fluid Mech.

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Trailing-edge serrations inspired by owls are capable of reducing broadband noise. In this study, the wall-resolved large-eddy simulations (LES) are carried out on the flow over NACA-0012 airfoil with additional serrated trailing edges. The computations are conducted with the high-order flux reconstruction method on unstructured meshes. Three kinds of serrations with different lengths are studied and compared with the straight trailing-edge case, and all three types of serration achieved a certain degree of noise reduction. Presently, the medium-length serration achieves the best noise reduction effect. The maximum decrease of overall sound pressure level is approximately 2.4 dB, implying that the length of serration has a substantial impact on the noise reduction effect. The serration has no significant effect on the upstream turbulence statistics, but it changes the flow structure near the serration, such as inducing side vortex pairs attached to the serration edges. Moreover, dynamic mode decomposition shows that the pressure structures vary with the serration length. For the most unstable hydrodynamic wave, the spanwise coherence of the mode structure of pressure in the upstream boundary layer is weakened. In addition, serrations can redistribute the dipole sources on the surfaces of airfoil and serrations. The destructive interference is enhanced to some extent, which is favourable for noise reduction. In contrast with LES simulations, the pure dipole analysis shows that the longest serration case seems to be the best. Furthermore, a recently developed noise theory is used to evaluate the influence of serrations on the flow noise sources qualitatively and quantitatively. It is found that the serrations can mitigate noise source intensity near the serration edges but increase the source intensity in the near wake. The combined effect of serration on the dipole source and flow noise source determines the overall noise reduction effect. To conclude, destructive interference plays a primary role in suppressing noise radiation by serrated trailing edges, and the dual effect of flow noise sources should be considered in future serration designs. As the influence of turbulence structure will make it more difficult to find the optimal serration parameters, the position of high-fidelity simulation will become increasingly important.

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Section: Resultsmentioning

confidence: 99%

Section: The Influence Of Serrations On Dipole Sourcesmentioning

confidence: 99%

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Noise reduction mechanisms for insert-type serrations of the NACA-0012 airfoil

Wan

et al. 2022

J. Fluid Mech.

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“…Bruneau et al [26] demonstrated that partial porous coatings can reduce drag on Ahmed bodies by up to 45%. Teruna et al [27] showed that a porous trailing edge on a NACA0018 aerofoil can reduce aerodynamic noise by up to 7 dB. Porous coatings have also been studied for reducing noise produced by vortex shedding for bluff bodies such as cylinders, as well as reducing their drag coefficients in certain cases.…”

Section: Porous Coatingsmentioning

confidence: 99%

Combined Passive/Active Flow Control of Drag and Lift Forces on a Cylinder in Crossflow Using a Synthetic Jet Actuator and Porous Coatings

2022

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This paper combines a synthetic jet actuator (SJA) and a leeward porous coating to alter the aerodynamic forces on a cylinder in crossflow at Re = 4.2 × 104. While SJAs and porous coatings are known to be effective flow control methods in isolation, their combined effect has not been studied. A 2D numerical model was created of a cylinder with a SJA at 90° and 100° leeward porous coating. The model was validated using accompanying water tunnel tests. The combined model was tested for dimensionless frequencies 0.15 <f+< 4 and compared to reference models. For f+< 1, using only the SJA increases the cylinder drag coefficient (Cd). Combining a porous coating with the SJA in that regime lowers the Cd values by 15–21%, and causes an overall reduction in Cd compared to the smooth cylinder baseline case. However, using only the porous coating causes a superior 35% reduction in Cd. For f+> 1, the combined SJA and porous coating configuration did not differ from the SJA only configuration, achieving the largest drag reduction of 45% at f+ = 4. The flow control mechanisms of the SJA and porous coating do not combine constructively in this current setup. However, the porous coating is beneficial for f+< 1, causing an overall drag reduction even when the active SJA tends to increase drag.

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“…Porous materials Similar to serrations, porous materials can be integrated into the structure of an airfoil to mitigate both self-noise [12][13][14] and turbulence-interaction noise [15][16][17][18]. At the leading edge, one possible mitigation mechanism for the turbulence-interaction noise is related to the damping of the deformation that is experienced by the turbulent vortices impinging on the airfoil surface.…”

Section: A Reduction Of Noise At the Sourcementioning

confidence: 99%

Development of the SmartAnswer Demonstrator: a Didactic Wind Tunnel for Aeroacoustic Applications

Tamaro

Zamponi

Schram

2022

28th AIAA/CEAS Aeroacoustics 2022 Conference

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A small didactic wind tunnel demonstrator has been designed and manufactured at the von Karman Institute for Fluid Dynamics to illustrate the physical principles at stake in flow-induced noise generation, offer an audible perception of the effectiveness of noise-mitigation strategies, and serve as a practical test bench for aeroacoustic education and research. Seven mitigation technologies are embedded in a single facility, which addresses the noise generation by an airfoil, noise propagation in a duct, and noise transmission through a flexible panel. A challenging objective of this facility was to offer a perceptible impression of various aeroacoustic noise mechanisms at low flow speeds and a live assessment of the effectiveness of the noisereduction technologies. Different approaches combining multiple microphones, advanced signal-processing techniques, and real-time audio feedback have been implemented to this end. The results establish that the demonstrator enables a clear perception of the effectiveness of the noise-mitigation technologies. The facility is also suitable for fast and inexpensive preliminary investigations of future noise-reduction concepts, taking advantage of rapid prototyping techniques.

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On the noise reduction of a porous trailing edge applied to an airfoil at lifting condition

Abstract: Paper published as part of the special topic on Special Issue on the Lattice Boltzmann Method This paper was selected as Featured This paper was selected as Scilight ARTICLES YOU MAY BE INTERESTED INAn interpretable framework of data-driven turbulence modeling using deep neural networks

Cited by 25 publications

References 52 publications

Noise reduction mechanisms for insert-type serrations of the NACA-0012 airfoil

Noise reduction mechanisms for insert-type serrations of the NACA-0012 airfoil

Combined Passive/Active Flow Control of Drag and Lift Forces on a Cylinder in Crossflow Using a Synthetic Jet Actuator and Porous Coatings

Development of the SmartAnswer Demonstrator: a Didactic Wind Tunnel for Aeroacoustic Applications

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