共查询到19条相似文献,搜索用时 109 毫秒
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等离子体激励器电极组相位不同便产生多相等离子体气动激励,建立了粒子图像测速仪流场参数测试系统,利用粒子图像测速仪技术,研究了非对称布局等离子体气动激励诱导空气流动特性,分析了多相等离子体气动激励对诱导空气流动速度的影响。结果表明:粒子图像测速仪流场测试系统能够准确地反映等离子体气动激励诱导空气流动的流场空间结构,等离子体气动激励诱导空气流动是平行于激励器的近壁面射流,多相等离子体气动激励能够增大等离子体气动激励诱导气流速度,或者使等离子体气动激励影响流场区域增大。粒子图像测速仪系统是深入研究等离子体气动激励的流场结构最佳的方式之一。 相似文献
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等离子体激励器电极组相位不同便产生多相等离子体气动激励,建立了粒子图像测速仪流场参数测试系统,利用粒子图像测速仪技术,研究了非对称布局等离子体气动激励诱导空气流动特性,分析了多相等离子体气动激励对诱导空气流动速度的影响。结果表明:粒子图像测速仪流场测试系统能够准确地反映等离子体气动激励诱导空气流动的流场空间结构,等离子体气动激励诱导空气流动是平行于激励器的近壁面射流,多相等离子体气动激励能够增大等离子体气动激励诱导气流速度,或者使等离子体气动激励影响流场区域增大。粒子图像测速仪系统是深入研究等离子体气动激励的流场结构最佳的方式之一。 相似文献
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颤振是航空发动机、燃气轮机等运行安全的重要威胁,但颤振稳定性与流动结构之间的关系尚不清晰。本文使用行波法和影响系数法,对某宽弦复合掠型高速跨音风扇转子的一阶模态进行了颤振特性研究,计算了在100%转速下从堵塞点到近失速点的颤振表现。使用影响系数法时,分析了不同通道数的计算域对气动阻尼计算的影响,并与行波法得到的结果进行了对比。研究了流动结构与叶片表面气动阻尼之间的关系,旨在提高对流动致颤机理的认识。结果表明影响系数法和行波法均能对叶片的气动阻尼进行较好的预测;流动结构方面,激波、激波附面层分离、叶尖泄漏流以及吸力面前缘叶顶附近的非定常压力波动,对叶片的气动阻尼分布有较大的影响。 相似文献
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引入负声源,导出了环形平面换能器声场的简洁表示式,计算了单个圆环、多个同心圆环同时激励及环阵相控聚焦声源产生的声场,分析了环的宽度、环数及聚焦点位置等因素对声场特征的影响。提出根据各阵元在声场中某点产生的声压的相位来确定各阵元电激励信号的延时,此方法较根据各阵元到该点的平均声程确定各阵元电激励信号的延时,能更难确地在该点实现聚焦。 相似文献
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通过同时求解机翼弹性运动方程和空气动力方程,对机翼的流固耦合问题进行了数值仿真,在空气动力计算中仔细地模拟了机翼在较大迎角时从机翼前缘和侧缘处卷起的分离涡。通过不同机翼、不同状态的仿真结果,发现如下结论:(1)机翼前缘或侧缘分离涡将使机翼颤振界速度降低,且机翼的基本迎角越大,颤振临界速度越低;(2)机翼前缘后掠角减小,分离涡对颤振性质的不利影响有所减缓;(3)在一定条件下,会出现稳定的极限环。 相似文献
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The interaction between the flow field and the sound field is responsible for the sound absorption at perforated acoustic liners with bias flow and has to be investigated contactlessly. Based on the optically measured flow velocity spectrum, an energy analysis was performed. As a result, the generation of broadband flow velocity fluctuations in the shear layer surrounding the bias flow caused by the flow sound interaction has been observed. In addition, the magnitude of this acoustically induced flow velocity oscillation exhibits a correlation with the acoustic dissipation coefficient of the bias flow liner. This supports the assumption that an energy transfer between the flow field and the sound field is responsible for the acoustic damping. 相似文献
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I.IntroductionAerodyntalcnoiseofturbomaChinrynotoalythectstheenvironmentbutalsosometimesresultsinstructuredamage.Aeroacoustics,asaintewhsciPlineofacousticsandaerodynamics,isattractingmorandmoreatteDtionandresearch.TherearetwoimportalltcontentsonthenoiseproducingmechAnsmsinaeroacousticproblem.OneisaboutthesourcesofnoiseinturbomachinryGenetallytherearethreetyPesofsources:thickness,forceandturbulencestress,correspondingrespectivelyTomonopole,dipoleandquadruplesourcesThelatertwokindsofsourcesh… 相似文献
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气动噪声随着列车运行速度的提高急剧增加,是高速列车噪声的重要组成部分。本文使用缩比为1:20的三车编组模型,通过三维瞬态延迟分离涡模型求解高速列车的外流场,分析了环境风对流场结构与声源特性的影响;之后使用FW-H方程进行噪声传播计算,分析了不同速度的环境风对高速列车气动声学行为特性的影响。结果表明:高速列车主要的噪声源分布在转向架附近,在环境风的影响下,列车背风侧声源强度高于迎风侧,列车底部声源强度增幅较大。10 m/s以内的环境风会改变高速列车在尾流区域的声学指向性,并使气动噪声增加2.1~8.7 dB。相关结论可以为高速列车气动声学设计等研究提供参考。 相似文献
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Active noise control in ducts: some physical insights 总被引:1,自引:0,他引:1
The mechanisms of active noise control in a duct are examined. Acoustical measurements are used to determine directly the acoustic power flow associated with both primary and secondary sources as a function of secondary to primary source strength ratio and volume velocity relative phase angles. A complete analytical model is also developed which allows calculation of individual source power flows and total downstream power flow as a function of source strengths and relative phase angles for finite size sources. It is evaluated for monopole and dual secondary source arrangements, but can be extended easily to any number of secondary sources. The model considers a finite size primary source in the plane of the duct cross section and evaluates the effect that the secondary sources have on the primary source power output. Measurements of individual source output powers and total downstream acoustic powers agree well with theoretical predictions. It is demonstrated that, for the monopole system, sound attenuation is achieved primarily by suppression of the primary source acoustic power output, with a little remaining power being absorbed by the secondary source. For the dual secondary source system, it is shown that the power is primarily absorbed by the secondary sources, but that, at phase and amplitude values slightly different to optimum, noise reduction is achieved by a combination of energy absorption and primary source power suppression. The analysis also demonstrates the dependence of the achievable noise reduction on secondary source size and location with respect to the primary source. 相似文献
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以亚临界三维圆柱绕流的气动噪声为对象,研究声类比理论中偶极子及四极子源模型在预测低Mach数流动气动声的可靠性及准确性。使用大涡模拟(LES)得到非定常流场,并依据声类比中的Curle等效偶极子面源和Lighthill四极子体源模型,提取相应的声源数据,经Fourier变换得到涡脱落频率处的声源信息,进而定量预测圆柱绕流的气动声。结果表明:Curle模型的结果与实验结果吻合良好,Lighthill体源模型预测的准确性依赖于声源区域截断,不恰当的声源截断将导致错误的声场预测。 相似文献
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I.D. Abrahams 《Journal of sound and vibration》1983,89(2):213-231
An elastic plate, set in an infinite baffle and immersed in a fluid moving with a uniform subsonic velocity, is excited by an acoustic source. The scattered sound field is analyzed when fluid-plate coupling is large, and a solution is found by the use of matched asymptotic expansions. The far field is found to approximate to the solution obtained when the elastic plate is absent. At a plate resonance, however, the outer field must include eigensolutions with singularities at the plate edges, and close to the plate the dominant terms are travelling plate waves. These plate waves are found to have a wavelength independent of the frequency of the source. It is also shown that a plate resonance corresponds to a divergence instability of aerodynamic flutter theory and that the stability results found in this paper are in agreement with those obtained by using modal expansions. The limit as the Mach number goes to zero is found to be singular, suggesting an analysis of the model for small flow velocity. This calculation is performed and the results match smoothly to the respective solutions for a stationary fluid and for a large subsonic flow. 相似文献
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On the acoustic boundary condition in the presence of flow 总被引:2,自引:0,他引:2
M.K. Myers 《Journal of sound and vibration》1980,71(3):429-434
The boundary condition on the acoustic perturbation velocity at an impermeable surface in a flow is considered for the cases in which the surface generates a sound field by vibration or is acoustically deformed by an incident sound field. It is shown that in general the condition is not equivalent to the requirement of continuity of acoustic particle displacement in the direction normal to the unperturbed surface. 相似文献