The Effects of Suction and Blowing on Tonal Noise Generation by Blunt Trailing Edges

Arias-Ramírez, Walter; Wolf, William

doi:10.2514/6.2015-2364

Cited by 10 publications

(15 citation statements)

References 7 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The computational domain extends 14 chords from the airfoil in each direction and the grids are symmetric with respect to the x-axis. Based on previous studies [31], all grids have 600 points in the wall-normal direction (N y = 600), which is sufficient to resolve the flow structures along the boundary layers considering the current wall-normal stretching. In all grids, the distance from the surface to the first mesh point is ∆y wall = 0.0002.…”

Section: Numerical Methodologymentioning

confidence: 99%

On secondary tones arising in trailing-edge noise at moderate Reynolds numbers

Ricciardi

Arias-Ramírez

Wolf

2020

European Journal of Mechanics - B/Fluids

View full text Add to dashboard Cite

Direct numerical simulations are carried out to investigate the flow features responsible for secondary tones arising in trailing-edge noise at moderate Reynolds numbers. Simulations are performed for a NACA 0012 airfoil at freestream Mach numbers 0.1, 0.2 and 0.3 for angle of incidence 0 deg. and for Mach number 0.3 at 3 deg. angle of incidence. The Reynolds number based on the airfoil chord is fixed at Re c = 10 5 . Flow configurations are investigated where noise generation arises from the scattering of boundary layer instabilities at the trailing edge. Results show that noise emission has a main tone with equidistant secondary tones, as discussed in literature. An interesting feature of the present flows at zero incidence is shown; despite the geometric symmetry, the flows become non-symmetric with a separation bubble only on one side of the airfoil. A separation bubble is also observed for the non-zero incidence flow. For both angles of incidence analyzed, it is shown that low-frequency motion of the separation bubbles induce a frequency modulation of the flow instabilities developed along the airfoil boundary layer. When the airfoil is at 0 deg. angle of attack an intense amplitude modulation is also observed in the flow quantities, resulting in a complex vortex interaction mechanism at the trailing edge. Both amplitude and frequency modulations directly affect the velocity and pressure fluctuations that are scattered at the trailing edge, what leads to secondary tones in the acoustic radiation.

show abstract

Section: Numerical Methodologymentioning

confidence: 99%

On secondary tones arising in trailing-edge noise at moderate Reynolds numbers

Ricciardi

Arias-Ramírez

Wolf

2020

European Journal of Mechanics - B/Fluids

View full text Add to dashboard Cite

show abstract

“…Thicker blunt trailing edges would have a lower tonal frequency compared to thinner ones at the same velocity [37]. Thicker airfoils produce higher amplitude, whereas thinner ones emit higher frequency tones [30]. Experimentally, noise increases as the bevel angle are increased until 8°.…”

Section: Factors Affecting Airfoil Noisementioning

confidence: 96%

“…Similarly, vortex shedding due to laminar boundary layer instabilities and blunt trailing edges are the dominant sources of airfoil self-noise [11]. Moreover, the interaction of wake and boundary layers was also associated with the airfoil tonal noise [30]. The discrete tones at the trailing edge are linked to the laminar boundary layer located on the pressure surface [31].…”

Section: Noise Generation Mechanism 21 Noise Generationmentioning

confidence: 99%

“…At low Reynolds number, high intensity centered frequency (fs) is accompanied by more pronounced secondary discrete tonal noise of frequency (fn) as freestream velocity increases [2]. Whereas at moderate Reynolds number, multiple tones superimposed on a broadband hump are generated [30]. Yet another suggestion was higher Mach number increases the amplitude and the frequency of the tone.…”

Section: Factors Affecting Airfoil Noisementioning

confidence: 99%

“…Thus, the boundary layer grows at different rates on both the suction and pressure sides. The suction side initially separate due to the unsteady behavior of the flow compared to the pressure side, which remains laminar over for relatively small angle of attack [30]. Airfoil tonal noise gradually decreases as the angle of attack increases from α = 0 0 before disappearing beyond α = 5 0 [2].…”

Section: Factors Affecting Airfoil Noisementioning

confidence: 99%

See 2 more Smart Citations

A Review on Generation and Mitigation of Airfoil Self-Induced Noise

Ibren

Andan

Asrar

et al. 2021

ARFMTS

View full text Add to dashboard Cite

A review on passive acoustic control of airfoil self-noise by means of porous trailing edge is presented. Porous surfaces are defined using various terms such as porosity, permeability, resistivity, porosity constant, dimensionless permeability, flow control severity and tortuosity. The primary purpose of this review paper is to provide key findings regarding the sources and mitigation techniques of self-induced noise generated by airfoils. In addition, various parametric design concepts were presented, which are critically important for porous-airfoil design specifications. Most research focus on experimentation with some recent efforts on numerical simulations. Detail study on flow topology is required to fully understand the unsteady flow nature. In general, noise on the airfoil surface is linked to the vortex shedding, instabilities on the surface, as well as feedback mechanism. In addition, acoustic scattering can be minimized by reducing extent of the porous region from the trailing edge while increasing resistivity. Moreover, blowing might also be another means of reducing noise near the trailing edge. Ultimately, understanding the flow physics well provides a way to unveil the unknowns in self-induced airfoil noise generation, mitigation, and control.

show abstract

Modification in airfoil’s tonal noise using periodic suction-blowing excitation

Kumar,

Bhumkar

2024

Journal of Sound and Vibration

View full text Add to dashboard Cite

The Effects of Suction and Blowing on Tonal Noise Generation by Blunt Trailing Edges

Cited by 10 publications

References 7 publications

On secondary tones arising in trailing-edge noise at moderate Reynolds numbers

On secondary tones arising in trailing-edge noise at moderate Reynolds numbers

A Review on Generation and Mitigation of Airfoil Self-Induced Noise

Modification in airfoil’s tonal noise using periodic suction-blowing excitation

Contact Info

Product

Resources

About