Effect of Leading-Edge Serrations on Helicopter Blade–Vortex Interaction Noise

Feinerman, Joel A.; Koushik, Sudarshan; Schmitz, Fredric H.

doi:10.4050/jahs.62.032001

Cited by 14 publications

(10 citation statements)

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“…Inspired by this, bionic edge design for leading and trailing edges of the rotor was performed by acquiring design elements from owl wings and feathers (Figure 3). In fact, sinusoidal structures were widely studied for leading edge design and proved to be effective in many cases [26,27,32]. In this case, the sinusoidal structure acquired from owl wings was reasonably modified and streamlined to reduce aerodynamic loss of the rotor.…”

Section: Structure Acquisition From Owl and Bionic Edge Designmentioning

confidence: 99%

Comparative Investigation on Improved Aerodynamic and Acoustic Performance of Abnormal Rotors by Bionic Edge Design and Rational Material Selection

Song

Wang

et al. 2022

Polymers

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Rotor plays a vital role in the dynamical system of an unmanned aerial vehicle (UAV). Prominent aerodynamic and acoustic performance are a long-term pursuit for the rotor. Inspired by excellent quiet flight characteristics of owls, this work adopted bionic edge design and rational material selection strategy to improve aerodynamic and acoustic performance of the rotor. A reference model of rotor prototype with streamlined edges was firstly generated by reverse engineering method. With inspiration from owl wings and feathers, bionic rotors with rational design on leading and trailing edges were obtained. Original and bionic rotors were fabricated with polyamide PA 12 and Resin 9400 by 3D printing technique. Aerodynamic and acoustic performance of the as-fabricated rotors were experimentally measured and analyzed in detail using a self-established test system. Comparative experimental results indicated that the aerodynamic and acoustic performance of the rotors was closely related to the bionic structures, material properties, and rotational speeds. At the same rotational speed, bionic rotor fabricated with Resin 9400 can produce a higher thrust than the prototype one and its power consumption was also reduced. The resulting noise of different bionic rotors and their directivities were comparatively investigated. The results verified the bionic edge design strategy can effectively control the turbulent flow field and smoothly decompose the airflow near the tailing edge, which resulting in enhancing the thrust and reducing the noise. This work could provide beneficial inspiration and strong clues for mechanical engineers and material scientists to design new abnormal rotors with promising aerodynamic and acoustic performance.

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Section: Structure Acquisition From Owl and Bionic Edge Designmentioning

confidence: 99%

Comparative Investigation on Improved Aerodynamic and Acoustic Performance of Abnormal Rotors by Bionic Edge Design and Rational Material Selection

Song

Wang

et al. 2022

Polymers

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“…However, leading-edge treatment approaches to reduce turbulence interaction noise also exist for axial fans, including leading-edge serrations [31][32][33][34][35][36] and porous materials [37][38][39]. In addition, modifications of the shape of the blades in the form of sweeping or skewing are known as effective means for noise reduction [3,[40][41][42][43][44].…”

Section: Introductionmentioning

confidence: 99%

Permeable Leading Edges for Airfoil and Fan Noise Reduction in Disturbed Inflow

Ocker

Geyer

Czwielong³

et al. 2021

AIAA Journal

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A detailed experimental study on the aerodynamic performance and noise emission of airfoils and fan blades with permeable leading edges under disturbed inflow conditions was performed. The airfoils and fan blades with permeable leading edges were made of an aluminum alloy using a powder bed fusion-based additive manufacturing process. In a first step, a wind-tunnel study was carried out. This consisted of detailed aerodynamic and aeroacoustic measurements on 16 airfoils with different permeable leading-edge designs that were performed for various flow speeds and geometric angles of attack. Based on the results from that study, unskewed fan blades with four different permeable leading-edge designs were manufactured in a second step. With the aim of reducing turbulence interaction noise of axial fans, the fans were examined with regard to their aerodynamic and acoustic properties under grid-generated turbulent inflow conditions. In a third step, a possible transfer of the observed noise emission from airfoils with permeable leading edge to that of fan blades was investigated. It was found that a notable broadband noise reduction can be transferred from airfoil applications to the sound spectra of axial fans. At the same time, the porous modifications can reduce the aerodynamic performance, and hence the fan efficiency.

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“…Nowadays, people have been increasingly realizing the value of strategies animals adopt. These biomimetic ideas have been inspiring researchers and are already applied on airfoils, propellers and even rudders [20][21][22].…”

Section: Introductionmentioning

confidence: 99%

Development of Mixed Flow Fans with Bio-Inspired Grooves

2019

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Mixed flow fan is a kind of widely used turbomachine, which has faced problems of further performance improvement in traditional design methods in recent decades. Inspired by the microgrooves such as riblets and denticles on bird feathers and shark skins, we here propose biomimetic designs of various blades with the bio-inspired grooves, aiming at the improvement of the aeroacoustic performance. Based on a systematic study with computational fluid dynamic analyses, we found that these designs had the potential in noise suppression even with macroscopic grooves. Our best design can suppress turbulence kinetic energy by approximately 38% at the blade leading edge with aerodynamic efficiency loss of only 0.3 percentage points. This improvement is achieved by passive flow control. The vortical structures are changed in a favorable way at the leading edge due to the grooves. We believe that these biomimetic designs could provide a promising future of enhancing the performance of mixed flow fans by making grooves of ideal flow passages on the suction faces of blades in accord with the theory of pump design.

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Effect of Leading-Edge Serrations on Helicopter Blade–Vortex Interaction Noise

Cited by 14 publications

References 0 publications

Comparative Investigation on Improved Aerodynamic and Acoustic Performance of Abnormal Rotors by Bionic Edge Design and Rational Material Selection

Comparative Investigation on Improved Aerodynamic and Acoustic Performance of Abnormal Rotors by Bionic Edge Design and Rational Material Selection

Permeable Leading Edges for Airfoil and Fan Noise Reduction in Disturbed Inflow

Development of Mixed Flow Fans with Bio-Inspired Grooves

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