Reduction of Flow Induced Tonal Noise Through Leading Edge Tubercle Modifications

Hansen, Kristy L.; Kelso, Richard; Doolan, Con J.

doi:10.2514/6.2010-3700

Cited by 73 publications

(72 citation statements)

References 12 publications

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“…Van Nierop et al [22] hypothesised that tubercles can effectively reduce airfoil tonal noise. Implementing TLE reduces tonal and broadband noise on the airfoils [50][51][52][53][54][55][56][57][58][59][60][61][62][63][64][65][66].…”

Section: Influence Of Tle On Tonal Noise and Broadband Noisementioning

confidence: 99%

Mimicking the humpback whale: An aerodynamic perspective

Aftab

Razak

Rafie

et al. 2016

Progress in Aerospace Sciences

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Section: Influence Of Tle On Tonal Noise and Broadband Noisementioning

confidence: 99%

Mimicking the humpback whale: An aerodynamic perspective

Aftab

Razak

Rafie

et al. 2016

Progress in Aerospace Sciences

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“…Hansen et al (2012) observed experimentally a reduction in aerofoil tonal noise by applying undulated (sinusoidal) LEs to a NACA0021 aerofoil at a Reynolds number of 1.2 × 10 5 . The formation of streamwise vortices behind the roots of the sinusoidal LE profile were identified as being the reason for the reduction in tonal self-noise by breaking up the coherence of vortex generation at the trailing edge.…”

Section: Introductionmentioning

confidence: 99%

On the reduction of aerofoil–turbulence interaction noise associated with wavy leading edges

2016

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An aerofoil leading-edge profile based on wavy (sinusoidal) protuberances/tubercles is investigated to understand the mechanisms by which they are able to reduce the noise produced through the interaction with turbulent mean flow. Numerical simulations are performed for non-lifting flat-plate aerofoils with straight and wavy leading edges (denoted by SLE and WLE, respectively) subjected to impinging turbulence that is synthetically generated in the upstream zone (freestream Mach number of 0.24). Full threedimensional Euler (inviscid) solutions are computed for this study thereby eliminating self-noise components. A high-order accurate finite-difference method and artefact-free boundary conditions are used in the current simulations. Various statistical analysis methods, including frequency spectra, are implemented to aid the understanding of the noise-reduction mechanisms. It is found with WLEs, unlike the SLE, that the surface pressure fluctuations along the leading edge exhibit a significant source cut-off effect due to geometric obliqueness which leads to reduced levels of radiated sound pressure. It is also found that there exists a phase interference effect particularly prevalent between the peak and the hill centre of the WLE geometry, which contributes to the noise reduction in the mid-to high-frequency range.

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“…Such geometry was originally considered for its aerodynamic properties (Miklosovic et al 2004;Johari et al 2007;Hansen et al 2011Hansen et al , 2016, and is inspired by the leading-edge protrusions (tubercles) of the humpback whale's pectoral flippers thought to be responsible for its impressive maneuverability when catching its prey (Fish et al 2008). One of the first attempts to quantify the aeroacoustic properties of WLEs was conducted by Hansen et al (2012), who through experiments based on a NACA0021 aerofoil identified that WLE cases obtained large tonal and broadband self-noise reductions within a certain frequency range. They theorised that the noise reductions were related to the production of streamwise vortices at the leading-edge troughs, which enhance the stability of the boundary layer by mixing in higher momentum fluid from the free stream altering the generation of vorticity near the trailing edge.…”

Section: Introductionmentioning

confidence: 99%

Aeroacoustic source mechanisms of a wavy leading edge undergoing vortical disturbances

Turner

Kim

2016

J. Fluid Mech.

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High-accuracy numerical simulations are performed to study aeroacoustic source mechanisms of wavy leading edges (WLE) on a thin aerofoil undergoing vortical disturbances. This canonical study is based on a prescribed spanwise vortex travelling downstream and creating secondary vortices as it passes through the aerofoil's leading edge. The primary aim of the study is to precisely understand the relationships between the vortexinduced velocity perturbation and the wall pressure fluctuation on the WLE geometry. It is observed that by increasing the size (amplitude) of the WLE the source strength at the peak region is reduced rapidly to a certain point and followed by a saturation stage, while at the root (trough) it remains fairly consistent regardless of the WLE size. This observation is demonstrated to be the consequence of three-dimensional vortex dynamics taking place along the WLE. One of the most profound features is that a system of horseshoe-like secondary vortices are created from the WLE peak region upon the impingement of the prescribed vortex. It is found that the horseshoe vortices produce significantly non-uniform velocity perturbation in front of the WLE leading to the disparity in the source characteristics between the peak and root. The alterations to the impinging velocity perturbation are carefully analysed and related to the wall pressure fluctuation in this study. In addition, a semi-analytic model based on Biot-Savart's law is developed to better understand and explain the role of the horseshoe vortex systems and the source mechanisms.

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Reduction of Flow Induced Tonal Noise Through Leading Edge Tubercle Modifications

Cited by 73 publications

References 12 publications

Mimicking the humpback whale: An aerodynamic perspective

Mimicking the humpback whale: An aerodynamic perspective

On the reduction of aerofoil–turbulence interaction noise associated with wavy leading edges

Aeroacoustic source mechanisms of a wavy leading edge undergoing vortical disturbances

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