Mechanisms of broadband noise generation on metal foam edges

Carpio, Alejandro Rubio; Avallone, Francesco; Ragni, Daniele; Snellen, Mirjam; Zwaag, Sybrand van der

doi:10.1063/1.5121248

Cited by 33 publications

(42 citation statements)

References 71 publications

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“…18,29 However, increasing d c also increases surface roughness which results in the increasing roughness noise at high frequencies. 13,15,18,21 For the 3D-printed perforated TE insert without the Kevlar sheet, despite having a broadband noise attenuation compared to the solid counterpart, a series of strong tonal peaks are observed as anticipated. In addition, noise increase due to roughness at high frequencies can also be seen.…”

Section: Narrow-band Noise Spectrasupporting

confidence: 56%

“…The increase of the pressure gradient may induce cross flow through the permeable material. This cross flow is likely to reduce the effectiveness of the pressure balancing mechanism 21 which contributes to the noise attenuation. Therefore, since the value of C indicates the ability of the material to withstand the cross flow resulting from the pressure gradient, 26 the noise attenuation capability provided by a permeable material with a larger C will have a lower tendency to become less effective when the angle of attack, i.e.…”

Section: Broadband Noise Attenuation and Variability With Angle Of Atmentioning

confidence: 99%

“…where l is the dynamic viscosity of the fluid, K is the permeability, q is the density of the fluid, C is the form drag coefficient, and r is the flow resistivity. These properties have widely been used in previous studies 13,14,21,31 for permeable material characterization. Extensive explanation of equation ( 1) can further be found in literature.…”

Section: Permeable Materials Characterizationmentioning

confidence: 99%

“…According to a recent investigation by Rubio Carpio et al., 21 the TBL-TE noise attenuation by such materials is obtained due to partial balancing of surface pressure fluctuations enabled by the permeability between the suction and the pressure sides. Such a mechanism was confirmed by the correlation of the near-surface velocity fluctuations between both sides across the porous metal-foam materials, measured with particle image velocimetry.…”

Section: Introductionmentioning

confidence: 99%

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An alternative permeable topology design space for trailing-edge noise attenuation

Luesutthiviboon

Ragni

Avallone

et al. 2021

International Journal of Aeroacoustics

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This study focuses upon a new permeable topology design concept as an alternative to porous metal foams, for turbulent boundary layer trailing-edge (TBL-TE) noise attenuation. The present permeable topology has unconventional characteristics with respect to the metal foams: a combination of low flow resistivity r and high form drag coefficient C. The unconventional characteristics are realized by a Kevlar-covered 3D-printed perforated structure. An experimental study featuring a NACA 0018 airfoil model with a Kevlar-covered 3D-printed TE insert at chord-based Reynolds numbers up to [Formula: see text] is carried out. The airfoil with this TE insert gives a broadband TBL-TE noise reduction up to approximately 5 dB, compared to a solid TE. This reduction varies only slightly with airfoil loading (lower than 1 dB variation), in contrast to the porous metal foams (up to 3 dB variation). When comparing the variation of noise attenuation given by all the permeable materials considered, the variation is found to decrease with the increasing C. This is because C specifies the permeable material's ability to withstand the increasing pressure difference, which causes cross flow that might interfere with the noise attenuation mechanism. Additionally, the drag coefficients as well as the roughness noise of the airfoil equipped with the present TE insert are also significantly lower than those of the metal-foam TE, and are mostly negligible compared to the fully solid airfoil. Based on the findings, design guidelines for permeable TE are proposed: the permeable material shall have a combination of a low flow resistivity and a high form drag coefficient as well as a negligible surface roughness.

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Section: Narrow-band Noise Spectrasupporting

confidence: 56%

Section: Broadband Noise Attenuation and Variability With Angle Of Atmentioning

confidence: 99%

Section: Permeable Materials Characterizationmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

An alternative permeable topology design space for trailing-edge noise attenuation

Luesutthiviboon

Ragni

Avallone

et al. 2021

International Journal of Aeroacoustics

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“…This observation led to the development of various TE noise reduction methods, which can be classified under two main categories, depending on the strategy that they rely on: (i) passive methods, where the physical and geometrical properties of the trailing edge are altered, such that the efficiency of the noise scattering is reduced, and (ii) active methods, which target the alteration of the hydrodynamic pressure field within the turbulent boundary layer upstream of the trailing edge. Examples of passive methods are the trailing edge serrations [10][11][12][13][14][15][16] , trailing edge brushes 17,18 , porous materials [19][20][21][22][23][24][25][26][27] , surface treatments [28][29][30][31][32][33] , shape optimization, morphing 34,35 , etc. Passive methods are often tailored to a given range of conditions (Reynolds number, angle of attack, etc.…”

Section: Introductionmentioning

confidence: 99%

Uniform flow injection into a turbulent boundary layer for trailing edge noise reduction

2020

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The hydrodynamic effects of inclined uniform continuous blowing on a turbulent boundary layer are investigated experimentally. A laminar flow is introduced into the boundary layer through a fence on a flat plate at a distance of 3.38δ 0 upstream of the trailing edge. The effects of this open-loop technique of flow control are examined at different angles of injection and at different blowing rates. Surface pressure fluctuations acquired from flushmounted microphones are used to estimate the trailing edge noise. Injection angles of 70 • and 90 • in combination with strong blowing rates enable a noise reduction of up to 15 dB at mid and high frequencies, f > 300 Hz. Similar aeroacoustic performances are obtained at a blowing angle of 50 • , but at lower blowing rates. At low frequencies a penalty is expected, with the trailing edge noise increasing for all the injection angles and blowing rates under analysis. Mean velocity profiles from hot-wire anemometry reveal that high injection angles and strong blowing rates induce a flow separation which is expected to deteriorate the aerodynamic performances. When applying a uniform blowing at 50 • , however, no flow separation occurs. From an aeroacoustic and aerodynamic point of view, uniform blowing applied at 50 • and at intermediate blowing rates is found to be the most promising setting.

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Decoupling Minimal Surface Metamaterial Properties Through Multi‐Material Hyperbolic Tilings

Callens

Arns

Kuliesh

et al. 2021

Adv Funct Materials

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Rapid advances in additive manufacturing have kindled widespread interest in the rational design of metamaterials with unique properties over the past decade. However, many applications require multi-physics metamaterials, where multiple properties are simultaneously optimized. This is challenging since different properties, such as mechanical and mass transport properties, typically impose competing requirements on the nano-/micro-/ meso-architecture of metamaterials. Here, a parametric metamaterial design strategy that enables independent tuning of the effective permeability and elastic properties is proposed. Hyperbolic tiling theory is applied to devise simple templates, based on which triply periodic minimal surfaces (TPMS) are partitioned into hard and soft regions. Through computational analyses, it is demonstrated how the decoration of hard, soft, and void phases within the TPMS substantially enhances their permeability-elasticity property space and offers high tunability in the elastic properties and anisotropy at constant permeability. Also shown is that this permeability-elasticity balance is well captured using simple scaling laws. The proposed concept is demonstrated through multi-material additive manufacturing of representative specimens. The approach, which is generalizable to other designs, offers a route towards multi-physics metamaterials that need to simultaneously carry a load and enable mass transport, such as load-bearing heat exchangers or architected tissue-substituting meta-biomaterials.

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Mechanisms of broadband noise generation on metal foam edges

Abstract: Note: This paper is part of the Special Topic on Passive and Active Control of Turbulent Flows.

Cited by 33 publications

References 71 publications

An alternative permeable topology design space for trailing-edge noise attenuation

An alternative permeable topology design space for trailing-edge noise attenuation

Uniform flow injection into a turbulent boundary layer for trailing edge noise reduction

Decoupling Minimal Surface Metamaterial Properties Through Multi‐Material Hyperbolic Tilings

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