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

2016 ◽  
Author(s):  
Saman Salehian ◽  
Lap D. Nguyen ◽  
Vladimir V. Golubev ◽  
Reda R. Mankbadi
Keyword(s):  
Far Field ◽  
Tonal Noise ◽  
Noise Radiation ◽  
Prediction Techniques

Experimental investigation of aerofoil tonal noise at low Mach number

2021 ◽  
Vol 932 ◽  
Author(s):  
Prateek Jaiswal ◽  
Yann Pasco ◽  
Gyuzel Yakhina ◽  
Stéphane Moreau
Keyword(s):  
Experimental Investigation ◽  
Mach Number ◽  
Three Dimensional ◽  
Normal Modes ◽  
Wall Pressure ◽  
Far Field ◽  
Tonal Noise ◽  
Trailing Edge ◽  
Modal Shape ◽  
Low Mach Number

This paper presents an experimental investigation of aerofoil tones emitted by a controlled-diffusion aerofoil at low Mach number ( $0.05$ ), moderate Reynolds number based on the chord length ( $1.4 \times 10^{5}$ ) and moderate incidence ( $5^{\circ }$ angle of attack). Wall-pressure measurements have been performed along the suction side of the aerofoil to reveal the acoustic source mechanisms. In particular, a feedback loop is found to extend from the aerofoil trailing edge to the regions near the leading edge where the flow encounters a mean favourable pressure gradient, and consists of acoustic disturbances travelling upstream. Simultaneous wall-pressure, velocity and far-field acoustic measurements have been performed to identify the boundary-layer instability responsible for tonal noise generation. Causality correlation between far-field acoustic pressure and wall-normal velocity fluctuations has been performed, which reveals the presence of a Kelvin–Helmholtz-type modal shape within the velocity disturbance field. Tomographic particle image velocimetry measurements have been performed to understand the three-dimensional aspects of this flow instability. These measurements confirm the presence of large two-dimensional rollers that undergo three-dimensional breakdown just upstream of the trailing edge. Finally, modal decomposition of the flow has been carried out using proper orthogonal decomposition, which demonstrates that the normal modes are responsible for aerofoil tonal noise. The higher normal modes are found to undergo regular modulations in the spanwise direction. Based on the observed modal shape, an explanation of aerofoil tonal noise amplitude reduction is given, which has been previously reported in modular or serrated trailing-edge aerofoils.

In‐Flight Far‐Field Measurement of Helicopter Impulsive Noise

1976 ◽  
Vol 21 (4) ◽  
pp. 2-16
Author(s):  
F. H. Schmitz ◽  
D. A. Boxwell
Keyword(s):  
High Speed ◽  
Impulsive Noise ◽  
Operating Conditions ◽  
Tape Recording ◽  
Far Field ◽  
Recording Equipment ◽  
Radiation Characteristics ◽  
Acoustic Data ◽  
Noise Radiation ◽  
The Subject

A new and highly successful method of collecting far‐field acoustic data radiated by helicopters in forward flight has been developed, utilizing a quiet aircraft flying in formation ahead of the subject helicopter. The lead aircraft, flown as an acoustic probe, was equipped with tape‐recording equipment and an external microphone. Spatial orientation of the helicopter with respect to the monitoring aircraft was achieved through visual flight reference. Far‐field acoustic data defining the impulsive noise radiation characteristics of the UH‐1H helicopter during high‐speed flight and partial ‐power descents have been gathered with this technique. Three distinct types of impulsive waveforms have been identified and correlated with helicopter steady operating conditions.

scholarly journals Aerodynamic and Aeroacoustic Analysis of a Harmonically Morphing Airfoil Using Dynamic Meshing

Acoustics ◽  
2021 ◽  
Vol 3 (1) ◽  
pp. 177-199
Author(s):  
Chawki Abdessemed ◽  
Abdessalem Bouferrouk ◽  
Yufeng Yao
Keyword(s):  
Large Scale ◽  
Computational Cost ◽  
Design Stage ◽  
Far Field ◽  
Acoustic Analogy ◽  
Tonal Noise ◽  
Eddy Simulation ◽  
Dynamic Meshing ◽  
Les Model ◽  
Naca 0012

This work explores the aerodynamic and aeroacoustic responses of an airfoil fitted with a harmonically morphing Trailing Edge Flap (TEF). An unsteady parametrization method adapted for harmonic morphing is introduced, and then coupled with dynamic meshing to drive the morphing process. The turbulence characteristics are calculated using the hybrid Stress Blended Eddy Simulation (SBES) RANS-LES model. The far-field tonal noise is predicted using the Ffowcs-Williams and Hawkings (FW-H) acoustic analogy method with corrections to account for spanwise effects using a correlation length of half the airfoil chord. At various morphing frequencies and amplitudes, the 2D aeroacoustic tonal noise spectra are obtained for a NACA 0012 airfoil at a low angle of attack (AoA = 4°), a Reynolds number of 0.62 × 106, and a Mach number of 0.115, respectively, and the dominant tonal frequencies are predicted correctly. The aerodynamic coefficients of the un-morphed configuration show good agreement with published experimental and 3D LES data. For the harmonically morphing TEF case, results show that it is possible to achieve up to a 3% increase in aerodynamic efficiency (L/D). Furthermore, the morphing slightly shifts the predominant tonal peak to higher frequencies, possibly due to the morphing TEF causing a breakup of large-scale shed vortices into smaller, higher frequency turbulent eddies. It appears that larger morphing amplitudes induce higher sound pressure levels (SPLs), and that all the morphing cases induce the shift in the main tonal peak to a higher frequency, with a maximum 1.5 dB reduction in predicted SPL. The proposed dynamic meshing approach incorporating an SBES model provides a reasonable estimation of the NACA 0012 far-field tonal noise at an affordable computational cost. Thus, it can be used as an efficient numerical tool to predict the emitted far-field tonal noise from a morphing wing at the design stage.

Far-field noise radiation characteristics of an afterburning military jet aircraft

2020 ◽  
Vol 148 (4) ◽  
pp. 2702-2702
Author(s):  
Michael S. Bassett ◽  
Reese D. Rasband ◽  
Daniel J. Novakovich ◽  
Kent L. Gee ◽  
Steven C. Campbell ◽  
...  
Keyword(s):  
Far Field ◽  
Radiation Characteristics ◽  
Noise Radiation ◽  
Field Noise

Open Counter-Rotation Fan Blades Optimization Based on 3D Inverse Problem Navier-Stokes Solution Method With the Aim of Tonal Noise Reduction

2008 ◽  
Author(s):  
Victor I. Mileshin ◽  
Michael A. Nyukhtikov ◽  
Igor K. Orekhov ◽  
Sergey V. Pankov ◽  
Sergey K. Shchipin
Keyword(s):  
Inverse Problem ◽  
Stokes Equations ◽  
Aerodynamic Characteristics ◽  
Tip Vortex ◽  
Navier Stokes ◽  
Far Field ◽  
Tonal Noise ◽  
Noise Sources ◽  
Navier Stokes Equations ◽  
Counter Rotation

When developing counter-rotating fans for advanced new-generation aeroengines with unducted blades it is very important to provide high acoustic and aerodynamic characteristics [1]. This paper presents some results of gasdynamic and aeroacoustic optimization of unducted CRF blade profile by using 3D viscous inverse problem. Flow in unducted CRF on the basis of unsteady 3D Navier-Stokes equations is modeled at the 1st stage of designing in order to find the key tonal noise sources. Based on these results, it is found that one of the key tonal noise sources is Rotor 1 - Rotor 2 tip vortices interaction and potential rotor interaction. Then, using 3D solver of the viscous inverse problem, aerodynamic loads are redistributed along R1 and R2 blade height aiming at a decrease in tip vortex intensity and potential rotor interaction with a probable increase in the CRF thrust. To verify the aerodynamic characteristics of the modified CRF, steady flow calculations are carried out with the help of 3D Navier-Stokes equations and “mixing plane” interfaces. To verify the acoustic characteristics of the modified CRF, tonal noise modeling is carried out for original and modified CRFs using aeroacoustic CIAM’s 3DAS solver for solution of unsteady inviscid equations for disturbances. Ffowcs–Williams, Howkings approach is used for acoustic calculations in the far field. The near acoustic field and directivity diagrams in the far field are found. Using 3D inverse problem, the fan tonal noise is decreased by 4 dB for take-0ff and landing with no thrust and efficiency losses.

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