Comparison of Far-Field Acoustic Prediction Techniques in Application to Tonal Noise Radiation of Transitional Airfoils

Salehian, Saman; Nguyen, Lap; Golubev, Vladimir V.; Mankbadi, Reda R.

doi:10.2514/6.2016-2849

Cited by 1 publication

(1 citation statement)

References 13 publications

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“…In the far-field, a Ffowcs-Williams and Hawkings (FWH) approach discussed in application to the current problem by Salehian et al [20] was utilized to generate the numerical spectra, with corrections made to the levels by accounting for the periodic boundary condition along the span, as suggested by Oberai et al [21]. As predicted, 3D ILES shows better agreement with the experimental measurements by continuing the trend of lower broadband levels and a near perfect match between 500 and 1500 Hz, compared to the 2D results.…”

Section: Spectral Analysis Of Surface and Far-field Pressure Data Sam...mentioning

confidence: 99%

Numerical Investigation of Tonal Trailing-Edge Noise Radiated by Low Reynolds Number Airfoils

et al. 2021

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A high-fidelity computational analysis carefully validated against concurrently obtained experimental results is employed to examine self-noise radiation of airfoils at transitional flow regimes, with a focus on elucidating the connection between the unsteady behavior of the laminar separation bubble (LSB) and the acoustic feedback-loop (AFL) resonant interactions observed in the airfoil boundary layers. The employed parametric study examines AFL sensitivity to the changes in the upstream flow conditions and the airfoil loading. Implicit Large-Eddy Simulations are performed for a NACA-0012 airfoil in selected transitional-flow regimes for which experimental measurements recorded characteristic multiple-tone acoustic spectra with a dual ladder-type frequency structure. The switch between the tone-producing and no-tone-producing regimes is traced to the LSB size and position as a function of the flow Reynolds number and the airfoil angle of attack, and further substantiated by the linear stability analysis. The results indicate a strong multi-tonal airfoil noise radiation associated with the AFL and attributed to the switch from the slowly-growing Tollmien–Schlichting to the fast-growing Kelvin–Helmholtz instabilities occurring in thin LSB regions when those are localized near the trailing-edge (TE) on either side of the airfoil. Such a process eventually results in the nonlinearly saturated flapping vortical modes (“rollers”) that scatter into acoustic waves at the TE.

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Section: Spectral Analysis Of Surface and Far-field Pressure Data Sam...mentioning

confidence: 99%

Numerical Investigation of Tonal Trailing-Edge Noise Radiated by Low Reynolds Number Airfoils

et al. 2021

View full text Add to dashboard Cite

show abstract

Comparison of Far-Field Acoustic Prediction Techniques in Application to Tonal Noise Radiation of Transitional Airfoils

Cited by 1 publication

References 13 publications

Numerical Investigation of Tonal Trailing-Edge Noise Radiated by Low Reynolds Number Airfoils

Numerical Investigation of Tonal Trailing-Edge Noise Radiated by Low Reynolds Number Airfoils

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