840 research outputs found

    Noise Measurement of a Wind Turbine using Thick Blades with Blunt Trailing Edge

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    The noise generated by wind turbines can potentially cause significant harm to the ecological environment and the living conditions of residents. Therefore, a proper assessment of wind turbine noise is crucial. The IEC 61400-11 standard provides standardized guidelines for measuring turbine noise, facilitating the comparison of noise characteristics among different wind turbine models. This work aims to conduct a comprehensive noise measurement of a 100kW wind turbine using thick blades with blunt trailing edge, which differs from the typical turbines studied previously. The work takes into account the unique design and dynamic characteristics of small-scale wind turbines and adjusts the measurement accordingly, with deviations from the IEC standards will be explicitly addressed

    Experimental Investigation of Airfoil Trailing Edge Noise Reduction by using TE Serrations

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    The growing prominence of aerodynamic noise from wind turbine blades at high wind speeds has made it the primary source of noise for wind turbines, with adverse effects on nearby residents' living conditions. This study focuses on experimental research conducted in an anechoic wind tunnel to investigate the noise reduction mechanism of wind turbine blade airfoils using serrated trailing edges, aiming to contribute to the development of low-noise wind turbine blades. Three models, including two types of NACA series airfoils and one reference plate with attachable serrated trailing edges, were tested. The findings reveal that airfoils with serrated trailing edges exhibit a 3 to 6 dB reduction in the mid-high frequency wideband noise, with the width of the frequency band of noise reduction slightly increasing as the Reynolds number rises. The presence of serrations also eliminates multiple tones of high amplitude exceeding 10 dB. The study highlights serration height as the most influential factor for noise reduction, surpassing the significance of serration width and the ratio of width to height. Moreover, investigations into the noise reduction mechanism indicate varying degrees of reduction in streamwise fluctuating velocity spectra near the serrated trailing edge, even aligning with changes in the sound power spectra. Serrations were found to alter the turbulence length scale in the downstream flow field, potentially impacting noise generation. This study suggests that the reduction in streamwise fluctuating velocity near the serrated trailing edge plays a crucial role in noise reduction, highlighting the importance of detailed flow field measurements and analysis for a comprehensive understanding of the mechanistic relationship between flow changes and serration-induced noise reduction

    14-Methoxy-2,16-dioxapentacyclo[7.7.5.01,21.03,8.010,15]henicosa-3(8),10,12,14-tetraene-7,20-dione

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    The title compound, C20H20O5, was synthesized from the reaction between 3-methoxysalicaldehyde and 1,3–cyclo­hexa­nedione in the presence of palladium(II) chloride. The two fused xanthene rings and one of the six-membered cyclo­hexane rings adopt envelope conformations, while the other six-membered cyclo­hexane ring is in a chair conformation. The mol­ecular packing is stabilized by weak inter­molecular C—H⋯O inter­actions

    9-(4-Chloro­phen­yl)-4a-hy­droxy-4,4a,5,6,9,9a-hexa­hydro-3H-xanthene-1,8(2H,7H)-dione

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    In the title compound, C19H19ClO4, the central fused ring and the attached cyclo­hexene ring adopt envelope conformations, while the cyclo­hexane ring adopts a chair conformation. The crystal packing is stabilized by O—H⋯O hydrogen bonds, which link the mol­ecules into a chain along the b axis. Weak C—H⋯O bonds also occur

    Reduced-order modeling of a sliding ring on an elastic rod with incremental potential formulation

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    Mechanical interactions between rigid rings and flexible cables are widespread in both daily life (hanging clothes) and engineering system (closing a tether net). A reduced-order method for the dynamic analysis of sliding rings on a deformable one-dimensional (1D) rod-like object is proposed. In contrast to discretize the joint rings into multiple nodes and edges for contact detection and numerical simulation, a single point is used to reduce the order of the numerical model. In order to achieve the non-deviation condition between sliding ring and flexible rod, a novel barrier functional is derived based on incremental potential theory, and the tangent frictional interplay is later procured by a lagged dissipative formulation. The proposed barrier functional and the associated frictional functional are C2C^{2} continuous, hence the nonlinear elastodynamic system can be solved variationally by an implicit time-stepping scheme. The numerical framework is first applied to simple examples where the analytical solutions are available for validation. Then, multiple complex practical engineering examples are considered to showcase the effectiveness of the proposed method. The simplified ring-to-rod interaction model can provide lifelike visual effect for picture animations, and also can support the optimal design for space debris removal system.Comment: 15 pages, 9 figure

    A review of the spider genus Chthonopes (Araneae, Theridiosomatidae), with descriptions of two new species from China

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    The genus Chthonopes Wunderlich, 2011 is reviewed in this paper. The type species Chthonopes jaegeri Wunderlich, 2011 was illustrated based on new material from the type locality and the new distribution records (Bolikhamsay and Ban Kouanphavang Khammouane, Laos). Two new species are described from Yunnan, China: C. bifidum Yu & Lin, sp. nov. (♂♀) and C. jimudeng Yu & Lin, sp. nov. (♀). A key is provided for the genus, as well as species diagnoses, and a distribution map for all five species of Chthonopes

    MX precipitate behavior in an irradiated advanced Fe-9Cr steel: Self-ion irradiation effects on phase stability

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    Reduced activation ferritic/martensitic (RAFM) steels are the leading candidate structural materials for first-wall and blanket components in fusion reactors. This work is the first in a series to provide a systematic roadmap of MX precipitate stability in RAFM steels under various ion irradiation conditions. Here, the MX-TiC precipitate behavior in an advanced Fe-9Cr RAFM steel is assessed under self-ion irradiation to damage levels ranging from 1 to 100 displacements per atom (dpa) at temperatures ranging from 300-600{\deg}C to isolate the effects of temperature and damage level on precipitate stability. The pre-existing MX-TiC precipitates are shown to exhibit temperature-dominated responses, including coarsening above 400{\deg}C at damage levels of 15 dpa, while damage levels studied at 50 dpa and higher showed dissolution across all temperature ranges studied. The effects of ballistic dissolution and diffusion on precipitate behavior are outlined as a function of precipitate characteristics (number density, size, and 25 volume fraction) and irradiation parameters with the use of the recoil resolution model of precipitate stability. This work provides critical insights into MX-TiC stability to high dose in-order to further optimize advanced steels with improved radiation resistance.Comment: 32 pages, 19 pages supplementa
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