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Amador GJ, van Oorschot BK, Liao C, Wu J, Wei D. Functional fibrillar interfaces: Biological hair as inspiration across scales. BEILSTEIN JOURNAL OF NANOTECHNOLOGY 2024; 15:664-677. [PMID: 38887525 PMCID: PMC11181169 DOI: 10.3762/bjnano.15.55] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 01/31/2024] [Accepted: 05/17/2024] [Indexed: 06/20/2024]
Abstract
Hair, or hair-like fibrillar structures, are ubiquitous in biology, from fur on the bodies of mammals, over trichomes of plants, to the mastigonemes on the flagella of single-celled organisms. While these long and slender protuberances are passive, they are multifunctional and help to mediate interactions with the environment. They provide thermal insulation, sensory information, reversible adhesion, and surface modulation (e.g., superhydrophobicity). This review will present various functions that biological hairs have been discovered to carry out, with the hairs spanning across six orders of magnitude in size, from the millimeter-thick fur of mammals down to the nanometer-thick fibrillar ultrastructures on bateriophages. The hairs are categorized according to their functions, including protection (e.g., thermal regulation and defense), locomotion, feeding, and sensing. By understanding the versatile functions of biological hairs, bio-inspired solutions may be developed across length scales.
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Affiliation(s)
- Guillermo J Amador
- Experimental Zoology Group, Department of Animal Sciences, Wageningen University & Research, De Elst 1, 6708 WD Wageningen, Netherlands
| | - Brett Klaassen van Oorschot
- Experimental Zoology Group, Department of Animal Sciences, Wageningen University & Research, De Elst 1, 6708 WD Wageningen, Netherlands
| | - Caiying Liao
- School of Aeronautics and Astronautics, Shenzhen Campus of Sun Yat-sen University, Shenzhen, 518107, China
| | - Jianing Wu
- School of Aeronautics and Astronautics, Shenzhen Campus of Sun Yat-sen University, Shenzhen, 518107, China
| | - Da Wei
- Beijing National Laboratory for Condensed Matter Physics and Laboratory of Soft Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
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Midmer A, Brücker C, Weger M, Wagner H, Bleckmann H. Interaction of barn owl leading edge serrations with freestream turbulence. BIOINSPIRATION & BIOMIMETICS 2024; 19:036014. [PMID: 38569525 DOI: 10.1088/1748-3190/ad3a4f] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/02/2023] [Accepted: 04/03/2024] [Indexed: 04/05/2024]
Abstract
The silent flight of barn owls is associated with wing and feather specialisations. Three special features are known: a serrated leading edge that is formed by free-standing barb tips which appears as a comb-like structure, a soft dorsal surface, and a fringed trailing edge. We used a model of the leading edge comb with 3D-curved serrations that was designed based on 3D micro-scans of rows of barbs from selected barn-owl feathers. The interaction of the flow with the serrations was measured with Particle-Image-Velocimetry in a flow channel at uniform steady inflow and was compared to the situation of inflow with freestream turbulence, generated from the turbulent wake of a cylinder placed upstream. In steady uniform flow, the serrations caused regular velocity streaks and a flow turning effect. When vortices of different size impacted the serrations, the serrations reduced the flow fluctuations downstream in each case, exemplified by a decreased root-mean-square value of the fluctuations in the wake of the serrations. This attenuation effect was stronger for the spanwise velocity component, leading to an overall flow homogenization. Our findings suggest that the serrations of the barn owl provide a passive flow control leading to reduced leading-edge noise when flying in turbulent environments.
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Affiliation(s)
- Alden Midmer
- City, University of London, Northampton Square 10, EC1V0HB London, United Kingdom
| | - Christoph Brücker
- City, University of London, Northampton Square 10, EC1V0HB London, United Kingdom
| | - Matthias Weger
- Institute of Biology II, RWTH Aachen University, Aachen, Germany
| | - Hermann Wagner
- Institute of Biology II, RWTH Aachen University, Aachen, Germany
| | - Horst Bleckmann
- Institute of Zoology, Rheinische Friedrich-Wilhelms Universität Bonn, Bonn, Germany
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3
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Omidvarnia F, Sarhadi A. Nature-Inspired Designs in Wind Energy: A Review. Biomimetics (Basel) 2024; 9:90. [PMID: 38392136 PMCID: PMC10886931 DOI: 10.3390/biomimetics9020090] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2024] [Revised: 01/24/2024] [Accepted: 01/26/2024] [Indexed: 02/24/2024] Open
Abstract
The field of wind energy stands at the forefront of sustainable and renewable energy solutions, playing a pivotal role in mitigating environmental concerns and addressing global energy demands. For many years, the convergence of nature-inspired solutions and wind energy has emerged as a promising avenue for advancing the efficiency and sustainability of wind energy systems. While several research endeavors have explored biomimetic principles in the context of wind turbine design and optimization, a comprehensive review encompassing this interdisciplinary field is notably absent. This review paper seeks to rectify this gap by cataloging and analyzing the multifaceted body of research that has harnessed biomimetic approaches within the realm of wind energy technology. By conducting an extensive survey of the existing literature, we consolidate and scrutinize the insights garnered from diverse biomimetic strategies into design and optimization in the wind energy domain.
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Affiliation(s)
- Farzaneh Omidvarnia
- Department of Wind and Energy Systems, Technical University of Denmark (DTU), Frederiksborgvej 399, 4000 Roskilde, Denmark
| | - Ali Sarhadi
- Department of Wind and Energy Systems, Technical University of Denmark (DTU), Frederiksborgvej 399, 4000 Roskilde, Denmark
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Rong J, Jiang Y, Murayama Y, Ishibashi R, Murakami M, Liu H. Trailing-edge fringes enable robust aerodynamic force production and noise suppression in an owl wing model. BIOINSPIRATION & BIOMIMETICS 2023; 19:016003. [PMID: 37939389 DOI: 10.1088/1748-3190/ad0aa9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/29/2023] [Accepted: 11/08/2023] [Indexed: 11/10/2023]
Abstract
As one of the unique owl-wing morphologies, trailing-edge (TE) fringes are believed to play a critical role in the silent flight of owls and have been widely investigated using idealized single/tandem airfoils. However, the effect of TE fringes and associated mechanisms on the aeroacoustics of owl wings, which feature curved leading edges, wavy TEs, and several feather slots at the wingtips, have not yet been addressed. In this study, we constructed two 3D owl wing models, one with and one without TE fringes, based on the geometric characteristics of a real owl wing. Large-eddy simulations and the Ffowcs Williams‒Hawkings analogy were combined to resolve the aeroacoustic characteristics of the wing models. Comparisons of the computed aerodynamic forces and far-field acoustic pressure levels demonstrate that the fringes on owl wings can robustly suppress aerodynamic noise while sustaining aerodynamic performance comparable to that of a clean wing. By visualizing the near-field flow dynamics in terms of flow and vortex structures as well as flow fluctuations, the mechanisms of TE fringes in owl wing models are revealed. First, the TE fringes on owl wings are reconfirmed to robustly suppress flow fluctuations near the TE by breaking up large TE vortices. Second, the fringes are observed to effectively suppress the shedding of wingtip vortices by mitigating the flow interaction between feathers (feather-slot interaction). These complementary mechanisms synergize to enhance the robustness and effectiveness of the TE fringe effects in owl wing models, in terms of aerodynamic force production and noise suppression. This study thus deepens our understanding of the role of TE fringes in real owl flight gliding and points to the validity and feasibility of employing owl-inspired TE fringes in practical applications of low-noise fluid machinery.
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Affiliation(s)
- Jiaxin Rong
- Shanghai Jiao Tong University and Chiba University International Cooperative Research Center (SJTU-CU ICRC), 800 Dongchuan Road, Minhang District, Shanghai 200240, People's Republic of China
- Graduate School of Engineering, Chiba University, 1-33, Yayoi-cho, Inage-ku, Chiba 263-8522, Japan
| | - Yajun Jiang
- Graduate School of Science and Engineering, Chiba University, 1-33, Yayoi-cho, Inage-ku, Chiba 263-8522, Japan
| | - Yuta Murayama
- Graduate School of Science and Engineering, Chiba University, 1-33, Yayoi-cho, Inage-ku, Chiba 263-8522, Japan
| | - Ryoto Ishibashi
- Graduate School of Science and Engineering, Chiba University, 1-33, Yayoi-cho, Inage-ku, Chiba 263-8522, Japan
| | - Masashi Murakami
- Graduate School of Science, Chiba University, 1-33, Yayoi-cho, Inage-ku, Chiba 263-8522, Japan
| | - Hao Liu
- Shanghai Jiao Tong University and Chiba University International Cooperative Research Center (SJTU-CU ICRC), 800 Dongchuan Road, Minhang District, Shanghai 200240, People's Republic of China
- Graduate School of Engineering, Chiba University, 1-33, Yayoi-cho, Inage-ku, Chiba 263-8522, Japan
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Saussaman T, Nafi A, Charland D, Ben-Gida H, Gurka R. The role of leading-edge serrations in controlling the flow over owls' wing. BIOINSPIRATION & BIOMIMETICS 2023; 18:066001. [PMID: 37650253 DOI: 10.1088/1748-3190/acf540] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/06/2023] [Accepted: 08/30/2023] [Indexed: 09/01/2023]
Abstract
We studied the effects of leading-edge serrations on the flow dynamics developed over an owl wing model. Owls are predatory birds. Most owl species are nocturnal, with some active during the day. The nocturnal ones feature stealth capabilities that are partially attributed to their wing microfeatures. One of these microfeatures is small rigid combs (i.e. serrations) aligned at an angle with respect to the incoming flow located at the wings' leading-edge region of the primaries. These serrations are essentially passive flow control devices that enhance some of the owls' flight characteristics, such as aeroacoustics and, potentially, aerodynamics. We performed a comparative study between serrated and non-serrated owl wing models and investigated how the boundary layer over these wings changes in the presence of serrations over a range of angles of attack. Using particle image velocimetry, we measured the mean and turbulent flow characteristics and analyzed the flow patterns within the boundary layer region. Our experimental study suggests that leading-edge serrations modify the boundary layer over the wing at all angles of attack, but not in a similar manner. At low angles of attack (<20°), the serrations amplified the turbulence activity over the wing planform without causing any significant change in the mean flow. At 20° angle of attack, the serrations act to suppress existing turbulence conditions, presumably by causing an earlier separation closer to the leading-edge region, thus enabling the flow to reattach prior to shedding downstream into the wake. Following the pressure Hessian equation, turbulence suppression reduces the pressure fluctuations gradients. This reduction over the wing would weaken, to some extent, the scattering of aerodynamic noise in the near wake region.
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Affiliation(s)
- Tanner Saussaman
- Physics and Engineering Science, Coastal Carolina University, Conway, SC, United States of America
| | - Asif Nafi
- Physics and Engineering Science, Coastal Carolina University, Conway, SC, United States of America
| | - David Charland
- Mechanical and Aerospace Engineering, George Washington University, Washington, DC, United States of America
| | - Hadar Ben-Gida
- Institute for Aerospace Studies, University of Toronto, Toronto, ON, Canada
| | - Roi Gurka
- Physics and Engineering Science, Coastal Carolina University, Conway, SC, United States of America
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Sun J, Yonezawa K, Shima E, Liu H. Integrated Evaluation of the Aeroacoustics and Psychoacoustics of a Single Propeller. INTERNATIONAL JOURNAL OF ENVIRONMENTAL RESEARCH AND PUBLIC HEALTH 2023; 20:1955. [PMID: 36767321 PMCID: PMC9916067 DOI: 10.3390/ijerph20031955] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 11/08/2022] [Revised: 01/16/2023] [Accepted: 01/16/2023] [Indexed: 06/18/2023]
Abstract
Aeroacoustic noise in multiple rotor drones has been increasingly recognized as a crucial issue, while noise reduction is normally associated with a trade-off between aerodynamic performance and sound suppression as well as sound quality improvement. Here, we propose an integrated methodology to evaluate both aeroacoustics and psychoacoustics of a single propeller. For a loop-type propeller, an experimental investigation was conducted in association with its aerodynamic and acoustic characteristics via a hover stand test in an anechoic chamber; the psychoacoustic performance was then examined with psychoacoustic annoyance models to evaluate five psychoacoustic metrics comprising loudness, fluctuation strength, roughness, sharpness, and tonality. A comparison of the figure of merit (FM), the overall sound pressure level (OASPL) and psychoacoustic metrics was undertaken among a two-blade propeller, a four-blade propeller, the loop-type propeller, a wide chord loop-type propeller, and a DJI Phantom III propeller, indicating that the loop-type propeller enables a remarkable reduction in OASPL and a noticeable improvement in sound quality while achieving comparable aerodynamic performance. Furthermore, the psychoacoustic analysis demonstrates that the loop-type propeller can improve the psychological response to various noises in terms of the higher-level broadband and lower-level tonal noise components. It is thus verified that the integrated evaluation methodology of aeroacoustics and psychoacoustics can be a useful tool in the design of low-noise propellers in association with multirotor drones.
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Affiliation(s)
- Jianwei Sun
- Graduate School of Engineering, Chiba University, Chiba 263-8522, Japan
| | - Koichi Yonezawa
- Central Research Institute of Electrical Power Industry, Abiko 270-1194, Japan
- Center for Aerial Intelligent Vehicles, Chiba University, Chiba 263-8522, Japan
| | - Eiji Shima
- Japan Aerospace Exploration Agency, Tokyo 181-0015, Japan
| | - Hao Liu
- Graduate School of Engineering, Chiba University, Chiba 263-8522, Japan
- Center for Aerial Intelligent Vehicles, Chiba University, Chiba 263-8522, Japan
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Song W, Mu Z, Wang Y, Zhang Z, Zhang S, Wang Z, Li B, Zhang J, Niu S, Han Z, Ren L. Comparative Investigation on Improved Aerodynamic and Acoustic Performance of Abnormal Rotors by Bionic Edge Design and Rational Material Selection. Polymers (Basel) 2022; 14:polym14132552. [PMID: 35808599 PMCID: PMC9269470 DOI: 10.3390/polym14132552] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2022] [Revised: 06/17/2022] [Accepted: 06/20/2022] [Indexed: 02/04/2023] Open
Abstract
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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Affiliation(s)
- Wenda Song
- Key Laboratory of Bionic Engineering of Ministry of Education, Jilin University, Changchun 130022, China; (W.S.); (Y.W.); (Z.Z.); (S.Z.); (Z.W.); (B.L.); (J.Z.); (S.N.); (Z.H.); (L.R.)
| | - Zhengzhi Mu
- Key Laboratory of Bionic Engineering of Ministry of Education, Jilin University, Changchun 130022, China; (W.S.); (Y.W.); (Z.Z.); (S.Z.); (Z.W.); (B.L.); (J.Z.); (S.N.); (Z.H.); (L.R.)
- School of Mechanical and Aerospace Engineering, Jilin University, Changchun 130022, China
- Correspondence:
| | - Yufei Wang
- Key Laboratory of Bionic Engineering of Ministry of Education, Jilin University, Changchun 130022, China; (W.S.); (Y.W.); (Z.Z.); (S.Z.); (Z.W.); (B.L.); (J.Z.); (S.N.); (Z.H.); (L.R.)
| | - Zhiyan Zhang
- Key Laboratory of Bionic Engineering of Ministry of Education, Jilin University, Changchun 130022, China; (W.S.); (Y.W.); (Z.Z.); (S.Z.); (Z.W.); (B.L.); (J.Z.); (S.N.); (Z.H.); (L.R.)
| | - Shuang Zhang
- Key Laboratory of Bionic Engineering of Ministry of Education, Jilin University, Changchun 130022, China; (W.S.); (Y.W.); (Z.Z.); (S.Z.); (Z.W.); (B.L.); (J.Z.); (S.N.); (Z.H.); (L.R.)
| | - Ze Wang
- Key Laboratory of Bionic Engineering of Ministry of Education, Jilin University, Changchun 130022, China; (W.S.); (Y.W.); (Z.Z.); (S.Z.); (Z.W.); (B.L.); (J.Z.); (S.N.); (Z.H.); (L.R.)
- School of Mechanical and Aerospace Engineering, Jilin University, Changchun 130022, China
| | - Bo Li
- Key Laboratory of Bionic Engineering of Ministry of Education, Jilin University, Changchun 130022, China; (W.S.); (Y.W.); (Z.Z.); (S.Z.); (Z.W.); (B.L.); (J.Z.); (S.N.); (Z.H.); (L.R.)
- School of Mechanical and Aerospace Engineering, Jilin University, Changchun 130022, China
| | - Junqiu Zhang
- Key Laboratory of Bionic Engineering of Ministry of Education, Jilin University, Changchun 130022, China; (W.S.); (Y.W.); (Z.Z.); (S.Z.); (Z.W.); (B.L.); (J.Z.); (S.N.); (Z.H.); (L.R.)
| | - Shichao Niu
- Key Laboratory of Bionic Engineering of Ministry of Education, Jilin University, Changchun 130022, China; (W.S.); (Y.W.); (Z.Z.); (S.Z.); (Z.W.); (B.L.); (J.Z.); (S.N.); (Z.H.); (L.R.)
| | - Zhiwu Han
- Key Laboratory of Bionic Engineering of Ministry of Education, Jilin University, Changchun 130022, China; (W.S.); (Y.W.); (Z.Z.); (S.Z.); (Z.W.); (B.L.); (J.Z.); (S.N.); (Z.H.); (L.R.)
| | - Luquan Ren
- Key Laboratory of Bionic Engineering of Ministry of Education, Jilin University, Changchun 130022, China; (W.S.); (Y.W.); (Z.Z.); (S.Z.); (Z.W.); (B.L.); (J.Z.); (S.N.); (Z.H.); (L.R.)
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Wang J, Ishibashi K, Joto M, Ikeda T, Fujii T, Nakata T, Liu H. Aeroacoustic characteristics of owl-inspired blade designs in a mixed flow fan: effects of leading- and trailing-edge serrations. BIOINSPIRATION & BIOMIMETICS 2021; 16:066003. [PMID: 34243175 DOI: 10.1088/1748-3190/ac1309] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/13/2021] [Accepted: 07/09/2021] [Indexed: 06/13/2023]
Abstract
There is an increasing need in industry for noise reduction in fans. Inspired by owls' silent flight, we propose four owl-inspired blade designs for a mixed-flow fan to examine whether leading-edge (LE) and/or trailing-edge (TE) serrations can resolve the tradeoff between sound suppression and aerodynamic performance. We investigate the blades' aeroacoustic characteristics through various experimental methods and large-eddy simulation (LES)-based numerical analyses. Experimental results suggest that 'slotted', simply-fabricated LE serrations can achieve a lowering of the noise level while sustaining the aerodynamic performance of the fan, whereas TE serrations fail. In addition, the inclination angle can improve LE serration performance in aeroacoustic and aerodynamic performance with a reduction in the specific noise level by around 1.4 dB. LES results and noise spectral analysis indicate that the LE serrations can suppress flow separation, reducing the broadband noise at low-to-middle frequencies (40-4k Hz). This passive-flow-control mechanism, likely due to local higher incidence angles associated with LE serrations, is capable of alleviating the intensive pressure gradient while suppressing wall-pressure fluctuations over the LE region, hence weakening the Kelvin-Helmholtz instability. The tonal noise also shows a marked reduction at the highest peak frequency associated with fan-vane interaction. Moreover, we find that the high-frequency noise by-product radiates mainly from the LE serrations andsurroundings, due to the small eddies broken up when the vortical flows pass through the LE serrations. Our results demonstrate that the biomimetic design of the LE serrations can facilitate the break-up of LE vortices passively and effectively without negatively impacting aerodynamic performance, which can be utilized as an effective device to improve the aeroacoustic performance of fan blades.
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Affiliation(s)
- Jinxin Wang
- Shanghai Jiao Tong University and Chiba University International Cooperative Research Center (SJTU-CU ICRC), 800 Dongchuan Road, Minhang District, Shanghai 200240, People's Republic of China
- Graduate School of Engineering, Chiba University, 1-33, Yayoi-cho, Inage-ku, Chiba 263-8522, Japan
| | - Kenta Ishibashi
- Graduate School of Engineering, Chiba University, 1-33, Yayoi-cho, Inage-ku, Chiba 263-8522, Japan
| | - Masaaki Joto
- Graduate School of Engineering, Chiba University, 1-33, Yayoi-cho, Inage-ku, Chiba 263-8522, Japan
| | - Teruaki Ikeda
- TERAL Inc., 230 Moriwake, Miyuki-cho, Fukuyama-shi, Hiroshima 720-0033, Japan
| | - Takeo Fujii
- TERAL Inc., 230 Moriwake, Miyuki-cho, Fukuyama-shi, Hiroshima 720-0033, Japan
| | - Toshiyuki Nakata
- Graduate School of Engineering, Chiba University, 1-33, Yayoi-cho, Inage-ku, Chiba 263-8522, Japan
| | - Hao Liu
- Shanghai Jiao Tong University and Chiba University International Cooperative Research Center (SJTU-CU ICRC), 800 Dongchuan Road, Minhang District, Shanghai 200240, People's Republic of China
- Graduate School of Engineering, Chiba University, 1-33, Yayoi-cho, Inage-ku, Chiba 263-8522, Japan
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Muthuramalingam M, Talboys E, Wagner H, Bruecker C. Flow turning effect and laminar control by the 3D curvature of leading edge serrations from owl wing. BIOINSPIRATION & BIOMIMETICS 2020; 16:026010. [PMID: 33137801 DOI: 10.1088/1748-3190/abc6b4] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/06/2020] [Accepted: 11/02/2020] [Indexed: 06/11/2023]
Abstract
This work describes a novel mechanism of laminar flow control of straight and backward swept wings with a comb-like leading edge (LE) device. It is inspired by the LE comb on owl feathers and the special design of its barbs, resembling a cascade of complex 3D-curved thin finlets. The details of the geometry of the barbs from an owl feather were used to design a generic model of the comb for experimental and numerical flow studies with the comb attached to the LE of a flat plate. Due to the owls demonstrating a backward sweep of the wing during gliding and flapping from live recordings, our examinations have also been carried out at differing sweep angles. The results demonstrate a flow turning effect in the boundary layer inboards, which extends downstream in the chordwise direction over distances of multiples of the barb lengths. The inboard flow-turning effect described here, counter-acts the outboard directed cross-span flow typically appearing for backward swept wings. This flow turning behaviour is also shown on SD7003 airfoil using precursory LES investigations. From recent theoretical studies on a swept wing, such a way of turning the flow in the boundary layer is known to attenuate crossflow instabilities and delay transition. A comparison of the comb-induced cross-span velocity profiles with those proven to delay laminar to turbulent transition in theory shows excellent agreement, which supports the laminar flow control hypothesis. Thus, the observed effect is expected to delay transition in owl flight, contributing to a more silent flight.
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Affiliation(s)
| | - Edward Talboys
- City, University of London, Northampton Square, London, EC1V 0HB, United Kingdom
| | - Hermann Wagner
- RWTH Aachen University, Templergraben 55, 52062 Aachen, Germany
| | - Christoph Bruecker
- City, University of London, Northampton Square, London, EC1V 0HB, United Kingdom
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10
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Rao C, Liu H. Effects of Reynolds Number and Distribution on Passive Flow Control in Owl-Inspired Leading-Edge Serrations. Integr Comp Biol 2020; 60:1135-1146. [PMID: 32805051 DOI: 10.1093/icb/icaa119] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
As a sophisticated micro device for noise reduction, the owl-inspired leading-edge (LE) serrations have been confirmed capable of achieving passive control of laminar-turbulent transition while normally paying a cost of lowering the aerodynamic performance in low Reynolds number (Re∼O[103]) regime. In order to explore potential applications of the owl-inspired serrated airfoils or blades in developing low noise wind turbines or multi-copters normally operating at higher Res, we conducted a large-eddy simulation (LES)-based study of Re effects on the aerodynamic performance of 2D clean and serrated models. Our results show that the LE serrations keep working effectively in mitigating turbulent fluctuations over a broad range of Re (O[103] ∼ O[105]), capable of achieving marked improvement in lift-to-drag ratio with increasing Res. As the aeroacoustic fields are in close association with the propagation of the turbulence sources, it is observed that the tradeoff between passive mitigation of turbulent fluctuations (hence aeroacoustic noise suppression) and aerodynamic performance can be noticeably mitigated at large angles of attack (AoAs) and at high Res. This indicates that the LE serrations present an alternative passive flow control mechanism at high Res through a straightforward local excitation of the flow transition while capable of mitigating the turbulent intensity passively. We further developed a 3D LES model of clean and partially serrated rectangular wings to investigate the effects of the LE serrations' distribution on aerodynamic features, on the basis of the observation that longer serrations are often distributed intensively in the mid-span of real owl's feathers. We find that the mid-span distributed LE serrations can facilitate the break-up of LE vortices and the turbulent transition passively and effectively while achieving a low level of turbulence kinetic energy over the upper suction surface of the wing.
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Affiliation(s)
- Chen Rao
- Shanghai Jiao Tong University and Chiba University International Cooperative Research Center (SJTU-CU ICRC), 800 Dongchuan Road, Minhang District, Shanghai, 200240, People's Republic of China.,Graduate School of Engineering, Chiba University, 1-33, Yayoi-cho, Inage-ku, Chiba, 263-8522, Japan
| | - Hao Liu
- Shanghai Jiao Tong University and Chiba University International Cooperative Research Center (SJTU-CU ICRC), 800 Dongchuan Road, Minhang District, Shanghai, 200240, People's Republic of China.,Graduate School of Engineering, Chiba University, 1-33, Yayoi-cho, Inage-ku, Chiba, 263-8522, Japan
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11
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Clark CJ, Jaworski JW. Introduction to the Symposium: Bio-Inspiration of Quiet Flight of Owls and Other Flying Animals: Recent Advances and Unanswered Questions. Integr Comp Biol 2020; 60:1025-1035. [PMID: 33220059 DOI: 10.1093/icb/icaa128] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Animal wings produce an acoustic signature in flight. Many owls are able to suppress this noise to fly quietly relative to other birds. Instead of silent flight, certain birds have conversely evolved to produce extra sound with their wings for communication. The papers in this symposium synthesize ongoing research in "animal aeroacoustics": the study of how animal flight produces an acoustic signature, its biological context, and possible bio-inspired engineering applications. Three papers present research on flycatchers and doves, highlighting work that continues to uncover new physical mechanisms by which bird wings can make communication sounds. Quiet flight evolves in the context of a predator-prey interaction, either to help predators such as owls hear its prey better, or to prevent the prey from hearing the approaching predator. Two papers present work on hearing in owls and insect prey. Additional papers focus on the sounds produced by wings during flight, and on the fluid mechanics of force production by flapping wings. For instance, there is evidence that birds such as nightbirds, hawks, or falcons may also have quiet flight. Bat flight appears to be quieter than bird flight, for reasons that are not fully explored. Several research avenues remain open, including the role of flapping versus gliding flight or the physical acoustic mechanisms by which flight sounds are reduced. The convergent interest of the biology and engineering communities on quiet owl flight comes at a time of nascent developments in the energy and transportation sectors, where noise and its perception are formidable obstacles.
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Affiliation(s)
- Christopher J Clark
- Department of Evolution, Ecology, and Organismal Biology, Spieth Hall, University of California, Riverside, CA 94720, USA
| | - Justin W Jaworski
- Department of Mechanical Engineering and Mechanics, Packard Laboratory, Lehigh University, Bethlehem, PA 18015, USA
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LePiane K, Clark CJ. Evidence that the Dorsal Velvet of Barn Owl Wing Feathers Decreases Rubbing Sounds during Flapping Flight. Integr Comp Biol 2020; 60:1068-1079. [DOI: 10.1093/icb/icaa045] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Synopsis
Owls have specialized feather features hypothesized to reduce sound produced during flight. One of these features is the velvet, a structure composed of elongated filaments termed pennulae that project dorsally from the upper surface of wing and tail feathers. There are two hypotheses of how the velvet functions to reduce sound. According to the aerodynamic noise hypothesis, the velvet reduces sound produced by aerodynamic processes, such as turbulence development on the surface of the wing. Alternatively, under the structural noise hypothesis, the velvet reduces frictional noise produced when two feathers rub together. The aerodynamic noise hypothesis predicts impairing the velvet will increase aerodynamic flight sounds predominantly at low frequency, since turbulence formation predominantly generates low frequency sound; and that changes in sound levels will occur predominantly during the downstroke, when aerodynamic forces are greatest. Conversely, the frictional noise hypothesis predicts impairing the velvet will cause a broadband (i.e., across all frequencies) increase in flight sounds, since frictional sounds are broadband; and that changes in sound levels will occur during the upstroke, when the wing feathers rub against each other the most. Here, we tested these hypotheses by impairing with hairspray the velvet on inner wing feathers (P1-S4) of 13 live barn owls (Tyto alba) and measuring the sound produced between 0.1 and 16 kHz during flapping flight. Relative to control flights, impairing the velvet increased sound produced across the entire frequency range (i.e., the effect was broadband) and the upstroke increased more than the downstroke, such that the upstroke of manipulated birds was louder than the downstroke, supporting the frictional noise hypothesis. Our results suggest that a substantial amount of bird flight sound is produced by feathers rubbing against feathers during flapping flight.
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Affiliation(s)
- Krista LePiane
- Department of Evolution, Ecology, and Organismal Biology, University of California, Riverside, CA 92520, USA
| | - Christopher J Clark
- Department of Evolution, Ecology, and Organismal Biology, University of California, Riverside, CA 92520, USA
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Simulation-Based Design and Optimization of Rectangular Micro-Cantilever-Based Aerosols Mass Sensor. SENSORS 2020; 20:s20030626. [PMID: 31979192 PMCID: PMC7037910 DOI: 10.3390/s20030626] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/02/2019] [Revised: 01/08/2020] [Accepted: 01/15/2020] [Indexed: 11/29/2022]
Abstract
Micro-Cantilever (MCL) is a thin film structure that is applied for aerosol particle mass sensing. Several modifications to the rectangular MCL (length-to-width ratio, slots at the anchor, serrations at its side edges) are made to deduce the role and influence of the shape of rectangular MCL-based aerosol mass sensors and reduce gas damping. A finite element fluid-structure interaction model was used to investigate the performance of MCL. It is found that (I) the mass sensitivity and quality factor decline with the increasing of length-to-width ratio which alters the resonant frequency of the MCL. The optimum conditions, including the length-to-width ratio (σlw = 5) and resonant frequency (f0 = 540.7 kHz) of the MCL, are obtained with the constant surface area (S = 45,000 μm2) in the frequency domain ranging from 0 to 600 kHz. (II) The slots can enhance the read-out signal and bring a small Q factor drop. (III) The edge serrations on MCL significantly reduce the gas damping. The results provide a reference for the design of aerosol mass sensor, which makes it possible to develop aerosol mass sensor with high frequency, sensitivity, and quality.
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Clark CJ, LePiane K, Liu L. Evolution and Ecology of Silent Flight in Owls and Other Flying Vertebrates. Integr Org Biol 2020; 2:obaa001. [PMID: 33791545 PMCID: PMC7671161 DOI: 10.1093/iob/obaa001] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
We raise and explore possible answers to three questions about the evolution and ecology of silent flight of owls: (1) do owls fly silently for stealth, or is it to reduce self-masking? Current evidence slightly favors the self-masking hypothesis, but this question remains unsettled. (2) Two of the derived wing features that apparently evolved to suppress flight sound are the vane fringes and dorsal velvet of owl wing feathers. Do these two features suppress aerodynamic noise (sounds generated by airflow), or do they instead reduce structural noise, such as frictional sounds of feathers rubbing during flight? The aerodynamic noise hypothesis lacks empirical support. Several lines of evidence instead support the hypothesis that the velvet and fringe reduce frictional sound, including: the anatomical location of the fringe and velvet, which is best developed in wing and tail regions prone to rubbing, rather than in areas exposed to airflow; the acoustic signature of rubbing, which is broadband and includes ultrasound, is present in the flight of other birds but not owls; and the apparent relationship between the velvet and friction barbules found on the remiges of other birds. (3) Have other animals also evolved silent flight? Wing features in nightbirds (nocturnal members of Caprimulgiformes) suggest that they may have independently evolved to fly in relative silence, as have more than one diurnal hawk (Accipitriformes). We hypothesize that bird flight is noisy because wing feathers are intrinsically predisposed to rub and make frictional noise. This hypothesis suggests a new perspective: rather than regarding owls as silent, perhaps it is bird flight that is loud. This implies that bats may be an overlooked model for silent flight. Owl flight may not be the best (and certainly, not the only) model for "bio-inspiration" of silent flight.
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Affiliation(s)
- Christopher J Clark
- Department of Evolution, Ecology, and Organismal Biology, University of California—Riverside, 900 University Avenue, Riverside, CA 92521, USA
| | - Krista LePiane
- Department of Evolution, Ecology, and Organismal Biology, University of California—Riverside, 900 University Avenue, Riverside, CA 92521, USA
| | - Lori Liu
- Department of Evolution, Ecology, and Organismal Biology, University of California—Riverside, 900 University Avenue, Riverside, CA 92521, USA
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Wang J, Nakata T, Liu H. Development of Mixed Flow Fans with Bio-Inspired Grooves. Biomimetics (Basel) 2019; 4:biomimetics4040072. [PMID: 31635361 PMCID: PMC6963329 DOI: 10.3390/biomimetics4040072] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2019] [Revised: 10/09/2019] [Accepted: 10/10/2019] [Indexed: 11/25/2022] Open
Abstract
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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Affiliation(s)
- Jinxin Wang
- School of Naval Architecture, Ocean and Civil Engineering, Shanghai Jiao Tong University, Shanghai 200240, China.
- Graduate School of Science and Engineering, Chiba University, Chiba 263-8522, Japan.
- Shanghai Jiao Tong University and Chiba University International Cooperative Research Center, Dongchuan Road 800, Shanghai 200240, China.
| | - Toshiyuki Nakata
- Graduate School of Science and Engineering, Chiba University, Chiba 263-8522, Japan.
| | - Hao Liu
- School of Naval Architecture, Ocean and Civil Engineering, Shanghai Jiao Tong University, Shanghai 200240, China.
- Graduate School of Science and Engineering, Chiba University, Chiba 263-8522, Japan.
- Shanghai Jiao Tong University and Chiba University International Cooperative Research Center, Dongchuan Road 800, Shanghai 200240, China.
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The Hydrodynamic Noise Suppression of a Scaled Submarine Model by Leading-Edge Serrations. JOURNAL OF MARINE SCIENCE AND ENGINEERING 2019. [DOI: 10.3390/jmse7030068] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
High hydrodynamic noise is a threat to the survival of underwater vehicles. We investigated a noise suppression mechanism by putting leading-edge serrations on the sail hull of a scaled SUBOFF model, through numerical calculation and an experimental test. We found that the cone shape of leading-edge serrations can decrease the intensity of the adverse pressure gradient and produce counter-rotation vortices, which destroy the formation of the horseshoe vortex and delay the tail vortex. To achieve the optimum hydrodynamic noise reduction, we summarized the parameters of leading-edge serrations. Then, two steel models were built, according to the simulation. We measured the hydrodynamic noise based on the reverberation method in a gravity water tunnel. The numerically calculated results were validated by the experimental test. The results show that leading-edge serrations with amplitudes of 0.025c and wavelengths of 0.05h can obtain hydrodynamic noise reduction of at least 6 dB, from 10 Hz to 2 kHz, where c is the chord length and h is the height of the sail hull. The results in our study suggest a new way to design underwater vehicles with low hydrodynamic noise at a high Reynolds number.
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Lawley J, Ben-Gida H, Krishnamoorthy K, Hackett EE, Kopp GA, Morgan G, Guglielmo CG, Gurka R. Flow Features of the Near Wake of the Australian Boobook Owl ( Ninox boobook) During Flapping Flight Suggest an Aerodynamic Mechanism of Sound Suppression for Stealthy Flight. Integr Org Biol 2019; 1:obz001. [PMID: 33793685 PMCID: PMC7671144 DOI: 10.1093/iob/obz001] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Abstract
The mechanisms associated with the ability of owls to fly silently have been the subject of scientific interest for many decades and may be relevant to bio-inspired design to reduce noise of flapping and non-flapping flying devices. Here, we characterize the near wake dynamics and the associated flow structures produced during flight of the Australian boobook owl (Ninox boobook). Three individual owls were flown at 8 ms-1 in a climatic avian wind tunnel. The velocity field in the wake was sampled at 500 Hz using long-duration high-speed particle image velocimetry (PIV) while the wing kinematics were imaged simultaneously using high speed video. The time series of velocity maps that were acquired over several consecutive wingbeat cycles enabled us to characterize the wake patterns and to associate them with the phases of the wingbeat cycle. We found that the owl wake was dramatically different from other birds measured under the same flow conditions (i.e., western sandpiper, Calidris mauri and European starling, Sturnus vulgaris). The near wake of the owl did not exhibit any apparent shedding of organized vortices. Instead, a more chaotic wake pattern was observed, in which the characteristic scales of vorticity (associated with turbulence) are substantially smaller in comparison to other birds. Estimating the pressure field developed in the wake shows that owls reduce the pressure Hessian (i.e., the pressure distribution) to approximately zero. We hypothesize that owls manipulate the near wake to suppress the aeroacoustic signal by controlling the size of vortices generated in the wake, which are associated with noise reduction through suppression of the pressure field. Understanding how specialized feather structures, wing morphology, or flight kinematics of owls contribute to this effect remains a challenge for additional study.
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Affiliation(s)
- Jonathan Lawley
- Department of Coastal and Marine Systems Science, Coastal Carolina University, Conway, SC 29579, USA
| | - Hadar Ben-Gida
- Faculty of Aerospace Engineering, Technion, Haifa 32000, Israel
| | - Krishnan Krishnamoorthy
- Department of Coastal and Marine Systems Science, Coastal Carolina University, Conway, SC 29579, USA
| | - Erin E Hackett
- Department of Coastal and Marine Systems Science, Coastal Carolina University, Conway, SC 29579, USA
| | - Gregory A Kopp
- Department of Civil and Environmental Engineering, University of Western Ontario, London,Ontario, Canada
| | | | | | - Roi Gurka
- Department of Coastal and Marine Systems Science, Coastal Carolina University, Conway, SC 29579, USA
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Thiria B. On flapping flight mechanisms and their applications to wind and marine energy harvesting. CURRENT OPINION IN INSECT SCIENCE 2018; 30:39-45. [PMID: 30553483 DOI: 10.1016/j.cois.2018.09.001] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/19/2018] [Revised: 08/30/2018] [Accepted: 09/01/2018] [Indexed: 06/09/2023]
Abstract
In this paper, we present a short review on some of significative results on insect flapping flight. In particular, we focus on the time varying shape mechanisms observed during the flapping cycle that are used by insects to enhance the production of aerodynamic force. We then discuss a few examples on how these mechanisms are adapted to energy harvesters in engineered applications.
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Affiliation(s)
- Benjamin Thiria
- Laboratoire de Physique et Mécanique des Milieux Hétérogènes (PMMH UMR 7636), CNRS, France; ESPCI Paris, PSL Research University, Sorbonne Université, France; Université Paris Diderot, Barre Cassan Bât. A, 7-9 quai St Bernard, 75252 Paris Cedex 05, France.
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Boonman A, Zadicario P, Mazon Y, Rabi C, Eilam D. The sounds of silence: Barn owl noise in landing and taking off. Behav Processes 2018; 157:484-488. [DOI: 10.1016/j.beproc.2018.06.011] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2018] [Revised: 06/14/2018] [Accepted: 06/18/2018] [Indexed: 11/27/2022]
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