scholarly journals An experimental study of airfoil instability tonal noise with trailing edge serrations

2013 ◽  
Vol 332 (24) ◽  
pp. 6335-6358 ◽  
Author(s):  
Tze Pei Chong ◽  
Phillip F. Joseph
Keyword(s):  
Experimental Study ◽  
Tonal Noise ◽  
Trailing Edge ◽  
Trailing Edge Serrations

Experimental study of wavy trailing edge serrations on flat rotor blades

2021 ◽  
Vol 263 (5) ◽  
pp. 1855-1866
Author(s):  
Sai Manikanta Kaja ◽  
K. Sriinivasan ◽  
A. Jaswanth Kalyan Kumar
Keyword(s):  
Experimental Study ◽  
Noise Reduction ◽  
Pitch Angle ◽  
Acoustic Emissions ◽  
Broadband Noise ◽  
Rotor Blades ◽  
Tonal Noise ◽  
Trailing Edge ◽  
Low Speeds ◽  
Trailing Edge Serrations

A detailed experimental study is conducted to observe the effect of various parameters like wavelength, depth of serrations, and pitch angle on serrated blades' acoustic emissions at low speeds up to 2000 rpm. Experiments are conducted on flat blade rotors with sinusoidal serrations on the trailing edge of blades with different amplitudes and wavelengths. A total of 7 blades with different serration configurations, including a base configuration, are studied, five of them have serrations throughout the span of the blade, and one configuration has serration of varying amplitude on the farther half of the blade. It is observed that some blade configurations have resulted in tonal noise reduction noise as much as 8dB, whereas some of the serration configurations reduce very little to none, there is no significant effect of T.E serrations on the broadband noise emitted by the rotor. Directivity of noise generated from the rotor, the effect of serrations on the directivity of the noise is studied.

The generation of tonal noise from sawtooth trailing-edge serrations at low Reynolds numbers

2016 ◽  
Vol 120 (1228) ◽  
pp. 971-983 ◽  
Author(s):  
D. J. Moreau ◽  
C. J. Doolan
Keyword(s):  
Reynolds Number ◽  
Low Reynolds Number ◽  
Leading Edge ◽  
Reynolds Numbers ◽  
Operating Conditions ◽  
Tonal Noise ◽  
Trailing Edge ◽  
Low Frequencies ◽  
Low Reynolds ◽  
Trailing Edge Serrations

ABSTRACTThe flow and noise created by sawtooth trailing-edge serrations has been studied experimentally at a low Reynolds number. Experiments have been performed on a flat-plate model with an elliptical leading edge and an asymmetrically bevelled trailing edge at Reynolds numbers of Rec = 1 × 105–1.3 × 105, based on chord. Wide serrations with a wavelength (λs) to amplitude (2h) ratio of λs/h = 0.6 were found to reduce the overall sound pressure level by up to 11dB. In contrast, narrower serrations with λs/h = 0.2 produce tonal noise and increase the overall noise level by up to 4dB. Intense vortices across the span of the trailing edge with narrow serrations are shown to be the source of tonal noise. Wide serrations reduce turbulent velocity fluctuations at low frequencies which explains the lower radiated noise. The narrow serrations that produce low Reynolds number tonal noise were shown previously to be effective at higher Reynolds numbers (Rec > 2 × 105), demonstrating that care is needed to fully understand the flow field over serrations for all intended operating conditions.

Experimental Study of the Performance of a Propeller with Trailing-Edge Serrations

2021 ◽  
Author(s):  
Yuliang Wei ◽  
Yujie Qian ◽  
Shiyuan Bian ◽  
Feng Xu ◽  
Deyi Kong
Keyword(s):  
Experimental Study ◽  
Trailing Edge ◽  
Trailing Edge Serrations

scholarly journals Optimization of Trailing-Edge Serrations to Reduce Open-Rotor Tonal Interaction Noise

2017 ◽  
Vol 140 (2) ◽  
Author(s):  
Robert Jaron ◽  
Antoine Moreau ◽  
Sébastien Guérin ◽  
Rainer Schnell
Keyword(s):  
Steady State ◽  
Noise Reduction ◽  
Hybrid Approach ◽  
Prediction Method ◽  
Rotor Blades ◽  
Spanwise Direction ◽  
Tonal Noise ◽  
Trailing Edge ◽  
Open Rotor ◽  
Trailing Edge Serrations

A major source of contra-rotating open rotor (CROR) tonal noise is caused by the interaction of the front-rotor (FR) wakes with the aft-rotor blades. Inspired by chevron nozzles, which increase the mixing process in jet shear layers, serrations are implemented at the FR trailing-edge in order to increase the wake mixing and thus reduce the tones. The depth and width of the serrations are optimized with a multi-objective, metamodel-assisted evolutionary algorithm. For each member, a steady-state Reynolds-averaged Navier–Stokes (RANS) simulation is performed, which is coupled with an analytical noise prediction method in order to evaluate the noise reduction due to the serrations. The results confirm that tonal interaction noise can be reduced by means of trailing-edge serrations. It is found that the major noise reduction mechanism for wake interaction is attributed to increased destructive interferences occurring in spanwise direction. The tonal noise generated through the interaction of the rear rotor (RR) potential field with the FR trailing edge is also slightly reduced because of the circumferential and axial shift of the serrated trailing edge. Furthermore, the present study demonstrates the feasibility of performing an acoustic optimization with a hybrid approach that predicts the noise analytically and extracts the aerodynamic input data from a steady-state RANS flow solution.

Numerical study on the airfoil self-noise of three owl-based wings with the trailing-edge serrations

2021 ◽  
pp. 095441002098822
Author(s):  
Dian Li ◽  
Xiaomin Liu ◽  
Lei Wang ◽  
Fujia Hu ◽  
Guang Xi
Keyword(s):  
Flow Field ◽  
Noise Reduction ◽  
Numerical Study ◽  
Barn Owl ◽  
Aerodynamic Noise ◽  
Frequency Noise ◽  
Trailing Edge ◽  
Reduction Mechanisms ◽  
Trailing Edge Serrations ◽  
Bionic Airfoil

Previous publications have summarized that three special morphological structures of owl wing could reduce aerodynamic noise under low Reynolds number flows effectively. However, the coupling noise-reduction mechanism of bionic airfoil with trailing-edge serrations is poorly understood. Furthermore, while the bionic airfoil extracted from natural owl wing shows remarkable noise-reduction characteristics, the shape of the owl-based airfoils reconstructed by different researchers has some differences, which leads to diversity in the potential noise-reduction mechanisms. In this article, three kinds of owl-based airfoils with trailing-edge serrations are investigated to reveal the potential noise-reduction mechanisms, and a clean airfoil based on barn owl is utilized as a reference to make a comparison. The instantaneous flow field and sound field around the three-dimensional serrated airfoils are simulated by using incompressible large eddy simulation coupled with the FW-H equation. The results of unsteady flow field show that the flow field of Owl B exhibits stronger and wider-scale turbulent velocity fluctuation than that of other airfoils, which may be the potential reason for the greater noise generation of Owl B. The scale and magnitude of alternating mean convective velocity distribution dominates the noise-reduction effect of trailing-edge serrations. The noise-reduction characteristic of Owl C outperforms that of Barn owl, which suggests that the trailing-edge serrations can suppress vortex shedding noise of flow field effectively. The trailing-edge serrations mainly suppress the low-frequency noise of the airfoil. The trailing-edge serration can suppress turbulent noise by weakening pressure fluctuation.

Experimental study of a cooling scheme for a turbine blade trailing edge

2015 ◽  
Vol 229 (8) ◽  
pp. 832-848 ◽  
Author(s):  
Ahmed Beniaiche ◽  
Adel Ghenaiet ◽  
Carlo Carcasci ◽  
Marco Pievarolli ◽  
Bruno Facchini
Keyword(s):  
Experimental Study ◽  
Turbine Blade ◽  
Trailing Edge
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