Self-noise and directivity of simple airfoils during stall: An experimental comparison

Laratro, Alex; Arjomandi, Maziar; Cazzolato, B.; Kelso, Richard

doi:10.1016/j.apacoust.2017.05.027

Cited by 15 publications

(9 citation statements)

References 10 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The two airfoils thus exhibit similar bulk body behaviors at very high angles of attack. Similar observation was made by Laratro et al [4] for a NACA0012 and a NACA0021 at very high angles of attack. 2) and = 0.01.…”

Section: Static Airfoilsupporting

confidence: 88%

“…For a static airfoil, it is well known that stall can lead to an increase of the amplitude of the emitted noise up to 10 dB at low frequencies compared to the trailing-edge noise of an attached turbulent boundary layer [2]. For a static airfoil at stall, two noise regimes are observed [3,4]. The light-stall regime is obtained close to the static stall angle and is characterized by a high amplitude broadband low frequency noise.…”

Section: Introductionmentioning

confidence: 99%

“…Experimental data investigating the effect of the camber and thickness of the airfoil on static stall noise is very limited. For the deep-stall regime, Laratro et al [4] observe that the thickness of the airfoil has a limited effect on its acoustic signature.…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Experimental characterization of the noise generated by an airfoil oscillating above stall

Raus

Cotté

Monchaux

et al. 2021

Aiaa Aviation 2021 Forum

View full text Add to dashboard Cite

The present work investigates the noise emitted by an airfoil oscillating above stall, thanks to synchronized surface pressure and far-field acoustic measurements in an anechoic open-jet wind tunnel. Both NACA0012 and a NACA63 3 418 airfoils are tested in order to investigate the effects of the airfoil shape on the static and dynamic stall noise. For static configurations, a smoother transition to stall noise is obtained for the cambered NACA63 3 418 airfoil, with a gradual increase and shift of the noise spectra at low frequencies as the separation point moves closer to the leading edge of the airfoil. Phase-averaged time-frequency analysis of the oscillating airfoil noise reveals that the light-stall noise and deep-stall noise regimes commonly observed for static airfoils also take place during the oscillations. Increasing the frequency of the oscillations leads to an increase of the duration and amplitude of the stall onset broadband noise, and a delay of the dynamic stall noise to greater angles of attack. In the same way, the dynamic stall noise is delayed for the NACA63 3 418 compared to the NACA0012, causing the stalled phase to be shorter for the NACA63 3 418. For the NACA0012, the noise does not depend on the angle of attack before the onset on stall. For the NACA63 3 418, the noise gradually increases in the pre-stall regime and the stall noise is preceded by a high amplitude separation noise.

show abstract

Section: Static Airfoilsupporting

confidence: 88%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Experimental characterization of the noise generated by an airfoil oscillating above stall

Raus

Cotté

Monchaux

et al. 2021

Aiaa Aviation 2021 Forum

View full text Add to dashboard Cite

show abstract

“…During stall the flow over the airfoil separates and, from an acoustic perspective, the blade begins to act as a bluff body in flow. For light stall conditions, airfoil noise generally increases in intensity by up to 5 485 dB and reduces the peak frequency [54].…”

Section: Tuning the Inflow Modelmentioning

confidence: 99%

An implementation of an aeroacoustic prediction model for broadband noise from a vertical axis wind turbine using a CFD informed methodology

Botha

Shahroki

Rice

2017

Journal of Sound and Vibration

View full text Add to dashboard Cite

This paper presents an enhanced method for predicting aerodynamically generated broadband noise produced by a Vertical Axis Wind Turbine (VAWT). The method improves on existing work for VAWT noise prediction and incorporates recently developed airfoil noise prediction models. Inflow-turbulence and airfoil self-noise mechanisms are both considered. Airfoil noise predictions are dependent on aerodynamic input data and time dependent Computational Fluid Dynamics (CFD) calculations are carried out to solve for the aerodynamic solution. Analytical flow methods are also benchmarked against the CFD informed noise prediction results to quantify errors in the former approach. Comparisons to experimental noise measurements for an existing turbine are encouraging. A parameter study is performed and shows the sensitivity of overall noise levels to changes in inflow velocity and inflow turbulence. Noise sources are characterised and the location and mechanism of the primary sources is determined, inflow-turbulence noise is seen to be the dominant source. The use of CFD calculations is seen to improve the accuracy of noise predictions when compared to the analytic flow solution as well as showing that, for inflow-turbulence noise sources, blade generated turbulence dominates the atmospheric inflow turbulence.16m. For a VAWT with an equivalent swept area, this corresponds to any machine with a diameter of less than 5m and span of 10m.Preliminary design of SWT's almost exclusively incorporates the use of low-or reduced-order prediction tools to make early performance estimates. Popular design tools such as QBlade [2] utilise methods such as the Double-Multiple Streamtube (DMS) [3] approach for aerodynamic performance estimates. Noise estimates 15 may subsequently be made based on these preliminary flow calculations.experimental results are available [16,17]. Experimental campaigns are mostly used to study overall performance as opposed to looking at detailed flow structures. Li et al. [16] performed a thorough investigation of the flow features around the blade of a VAWT, verifying CFD calculations against wind tunnel test data and showed that CFD calculations performed well when an appropriate turbulence model was applied. There are, however, some outstanding issues to be addressed when using CFD for VAWT aerodynamic prediction [18]. 50An example of this is the matter of grid dependency such as the study by Almohammadi et al. [19] showing the sensitivity of the power/torque calculations to mesh types and the time step/Courant number.The primary objectives of the present study are concerned with the development of a validated computational method for the prediction of noise generated by a VAWT. Additionally the new methods will make use of CFD calculations as input data to existing noise models since CFD calculations can be used 55 to efficiently (and more accurately) predict detailed flow features including turbulence parameters which are important inputs required for noise prediction models. Models for inflow-turbulence and ...

show abstract

“…Trailing-edge noise, and various methods to reduce it, have been extensively investigated since the advent of aeroacoustic research [3,4,5,1,6,7]. This is largely due to the dominance of this noise mechanism in most applications when operating in typical conditions [8,9]. Many models of airfoil self-noise relate the radiated far-field sound to the near-field hydrodynamics.…”

Section: Introductionmentioning

confidence: 99%

Steady and unsteady loading and radiated far-field sound of three NACA series airfoils in a uniform flow

Branch

Zang

Azarpeyvand

2022

28th AIAA/CEAS Aeroacoustics 2022 Conference

View full text Add to dashboard Cite

show abstract

Self-noise and directivity of simple airfoils during stall: An experimental comparison

Cited by 15 publications

References 10 publications

Experimental characterization of the noise generated by an airfoil oscillating above stall

Experimental characterization of the noise generated by an airfoil oscillating above stall

An implementation of an aeroacoustic prediction model for broadband noise from a vertical axis wind turbine using a CFD informed methodology

Steady and unsteady loading and radiated far-field sound of three NACA series airfoils in a uniform flow

Contact Info

Product

Resources

About