Flow topology and noise emission around straight, serrated and slitted trailing edges using the Lattice Boltzmann methodology

Velden, Wouter C. van der; Zuijlen, Alexander van; Ragni, Daniele

doi:10.2514/6.2016-3021

Cited by 11 publications

(7 citation statements)

References 25 publications

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“…The flow field has been computed using the commercial solver PowerFLOW 5.4b based on the lattice-Boltzmann method (LBM). The methodology has also been used previously to predict TBL-TE noise (van der Velden, van Zuijlen & Ragni 2016; Avallone, Van der Velden & Ragni 2017; Avallone et al. 2018; Romani, van der Velden & Casalino 2018).…”

Section: Methodsmentioning

confidence: 99%

Noise reduction mechanisms of an open-cell metal-foam trailing edge

et al. 2020

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Section: Methodsmentioning

confidence: 99%

Noise reduction mechanisms of an open-cell metal-foam trailing edge

et al. 2020

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“…Computations of the flow organization and acoustic propagation around trailing edge serrations have been conducted in the past [6,11,30,31,34]. By performing numerical analyses, both flow and pressure fields can be obtained and one has the advantage of overcoming the experimental limitations mentioned above.…”

Section: Introductionmentioning

confidence: 99%

Noise Reduction Mechanisms of an Airfoil with Trailing Edge Serrations at Low Mach Number

Tang

Lei

2019

Applied Sciences

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Trailing-edge serrations have proven to be valid applications of trailing edge noise mitigation for an airfoil, while the physical noise reduction mechanism has not been adequately studied. We performed simulations employing Large-eddy simulation and the Lighthill–Curle method to reveal the variation in the hydrodynamic field and sound source due to the trailing edge serrations. The grid resolution and computational results were validated against experimental data. The simulation results show that: the trailing edge serrations impede the growth of spanwise vortices and promote the development of streamwise vortices near the trailing edge and the wake; the velocity fluctuations in the vertical cross-section of the streamwise direction near the trailing edge are reduced for the serrated airfoil, thereby obviously reducing the strength of the pressure fluctuations near the trailing edge; and the trailing edge serrations decrease the distribution of the sound source near the trailing edge and reduce the local peak value of sound pressure level in a specific frequency range as well as the overall sound pressure level. Moreover, we observed that, in the flow around the NACA0012 airfoil, the location where the strong sound source distribution begins to appear is in good agreement with the location where the separated boundary layer reattaches. It is therefore effective to reduce trailing edge noise by applying serrations on the upstream of the reattachment point.

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“…Because of the complex flow field and of the streamwise varying pressure gradient, both aerodynamic effects and acoustic scattering are mutually dependent [3,23,24]. Flow measurements [7,10,24] and computations [22,25] showed that, even at small angles of attack, the turbulent flow tends to seep into the empty space in between serrations. More in details, both an outward (i.e., from the centerline toward the edge) and an inward (i.e., from the edge toward the centerline of the serrations) flow motions characterize the flow field respectively at the root and the tip of the sawtooth trailing-edge serrations [10,24].…”

Section: Introductionmentioning

confidence: 99%

Benefits of curved serrations on broadband trailing-edge noise reduction

Avallone

Velden

Ragni

2017

Journal of Sound and Vibration

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Far-field noise and flow field over a novel curved trailing-edge serration (named as iron-shaped serration) are investigated. Spectra of the far-field broadband noise, directivity plots and the flow-field over the iron-shaped serration are obtained from numerical computations performed using a compressible Lattice-Boltzmann solver. The new design is compared to a conventional trailing-edge serration with a triangular geometry. Both serration geometries were retrofitted to a NACA 0018 airfoil at zero degree angle of attack. The iron-shaped geometry is found to reduce far-field broadband noise of approximately 2 dB more than the conventional sawtooth serration for chord-based Strouhal numbers St c < 15. At higher frequencies, the far-field broadband noise for the two serration geometries has comparable intensity. Near-wall velocity distribution and surface pressure fluctuations show that their intensity and spectra are independent on the serration geometry, but a function of the streamwise location. It is found that the larger noise reduction achieved by the iron-shaped trailing-edge serration is due to the mitigation of the scattered noise at the root. This effect is obtained by mitigating the interaction between the two sides of the serration, by delaying toward the tip both the outward (i.e., the tendency of the flow to deviate from the centerline to the edge of the serration) and the downward (i.e., the tendency of the flow to merge between the upper and bottom side of the serration) flow motions present at the root of the sawtooth.

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Flow topology and noise emission around straight, serrated and slitted trailing edges using the Lattice Boltzmann methodology

Cited by 11 publications

References 25 publications

Noise reduction mechanisms of an open-cell metal-foam trailing edge

Noise reduction mechanisms of an open-cell metal-foam trailing edge

Noise Reduction Mechanisms of an Airfoil with Trailing Edge Serrations at Low Mach Number

Benefits of curved serrations on broadband trailing-edge noise reduction

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