An investigation of passive methods for airfoil noise reduction in laminar boundary layer instability flow regime

Krusz, Witold D.; Rarata, Zbigniew

doi:10.2514/6.2017-3367

Cited by 1 publication

(3 citation statements)

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“…To obtain flow fields of considered configurations of the NACA 0012 airfoil, the unsteady compressible Navier-Stokes equations were solved by means of the LES method. The computational approach was demonstrated and validated against the DNS and experimental data in the previous work by Krusz and Rarata (2017). The LES calculations were performed by using ANSYS Fluent finite volume code.…”

Section: Numerical Details and Test Casesmentioning

confidence: 99%

“…They found negligible effect of the trailing edge serrations on the tonal noise generation mechanism. Krusz and Rarata (2017) carried out a numerical study to investigate the mechanisms of airfoil noise reduction by passive methods at Reynolds number of 2 Â 10 5 , using the NACA 0012 airfoil shape. The numerical simulations were performed by means of a large eddy simulations (LES) approach, which was validated against DNS and aerodynamic experimental data.…”

Section: Introductionmentioning

confidence: 99%

“…Jones et al (2010), Ikeda et al (2012); Pando et al (2014); and Sandberg and Wheeler (2019) showed that the acoustic feedback loop can also be studied in terms of absolute instabilities based on flow fields obtained from DNS or LES. Krusz and Rarata (2017) showed that wavy surface modifications of the NACA 0012 airfoil can reduce significantly emission of tonal noise with modest impact on the aerodynamic performance. In this work, the mechanism of the tonal noise reduction when deploying surface irregularities, such as surface waviness, is investigated using spatial stability analyses.…”

Section: Introductionmentioning

confidence: 99%

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The effect of wavy surface on boundary layer instabilities of an airfoil

Rarata

2021

AEAT

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Purpose The purpose of this paper is to investigate airfoil’s tonal noise reduction mechanism when deploying surface irregularities, such as surface waviness by means of spatial stability analyses. Design/methodology/approach Flow field calculations over smooth and wavy-surface NACA 0012 airfoils at 2° angle of attack and at Reynolds number of 200,000 are performed using the large eddy simulation (LES) approach. Three geometrical configurations are considered: a smooth NACA 0012 airfoil, wavy surface on the suction side (SS) and wavy surface on the pressure side (PS). The spatial stability analyses using the LES-generated flow fields are conducted and validated against the Orr-Sommerfeld stability analysis for the smooth airfoil configuration. Findings The spatial stability analyses show that inclusion of the wavy-type modification on the SS of the airfoil does not lead to altering of the acoustic feedback loop mechanism, with respect to the mechanism observed for the smooth airfoil configuration. In contrast, applying the surface modifications to the airfoil PS leads to a significant reduction of the amplification range of disturbances in the vicinity of the trailing edge for the frequency of the acoustic feedback loop mechanism. Practical implications The spatial analyses using, for example, LES-generated flow fields can be widely used to determine acoustic sources and associated distributions of amplifications for a wide range of applications in the aeroacoustics. Originality/value The spatial stability analysis approach based on flow fields computed a priori using the LES method has been introduced, validated and used to determine behaviour of the acoustic feedback loop when accurate reconstruction of geometry effects is required.

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Section: Numerical Details and Test Casesmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%