共查询到19条相似文献,搜索用时 140 毫秒
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为了提高风力机钝尾缘翼型优化设计的精确性,提出设计变量计及尾缘厚度及其在中弧线上侧分配比的非对称钝尾缘翼型优化设计方法。采用风力机翼型型线集成理论和B样条曲线,建立钝尾缘翼型型线控制方程组。以翼型的形状函数系数、B样条控制参数以及钝尾缘厚度和其分配比为设计变量,利用粒子群算法耦合XFOIL软件进行钝尾缘翼型优化设计。针对S812翼型优化得到尾缘厚度2.61%c、厚度分配比0:1的钝尾缘改型,采用计算流体动力学方法研究翼型及其改型的气动性能和流场特性。结果表明:优化得到钝尾缘翼型的升力系数和最大升阻比均显著增大;钝尾缘翼型吸力面的气流在流场中发生下洗,改善了翼型表面压力分布,并引起翼型失速延迟,使得翼型的气动性能明显提高。 相似文献
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为研究仿生波状前缘对翼型失速性能的影响,本文采用S-A湍流模型,对风力机翼型NACA634-021(光滑前缘)以及对应的正弦波状前缘仿生翼型的绕流流场进行了数值模拟。结果表明,光滑翼型在20°攻角附近发生深度失速,升力系数骤然下降;而波状前缘仿生翼型有效改善了失速特性,升力系数变化较平稳,在大攻角下高于光滑翼型。通过流场分析发现光滑翼型失速前后升力系数骤然下降的主要原因在于前缘压力面和吸力面的压差大幅度下降,而仿生翼型改变了前缘的压力分布特性,进而改变了大攻角下的分离特性,促进流向涡对的产生和发展,使得凸峰附近保持附着流动,进而提高升力。 相似文献
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减缩频率和平均攻角对俯仰振荡翼型影响分析 总被引:1,自引:0,他引:1
《工程热物理学报》2017,(6)
本文以NACA0012翼型为研究对象,采用混合网格划分方法和SST κ-ω湍流模型,数值模拟了雷诺数Re=2.7×10~5条件下减缩频率和平均攻角对翼型俯仰振荡气动特性的影响。结果表明:翼型俯仰运动时的平均升力系数均低于静态条件下的升力系数;减缩频率对翼型下行段气动特性影响最为显著,当减缩频率较小时,翼型刚开始下行运动,出现流动分离越显著,这导致平均升力系数与静态条件下升力系数差值变大;平均攻角越大,俯仰运动时的最大升力系数越小;翼型俯仰运动上行段升力系数大,主要是因为前缘流动加速剧烈,增大了上下表面压差。 相似文献
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本文通过采用Transition-SST湍流模型对UMY02-T01-26风电机组专用翼型绕流流场的数值计算,探究了湍流强度对风力机翼型气动性能的影响。结果表明,随着湍流强度的提高,翼型升力系数由前缘失速转变为混合失速。在一定的攻角范围内,升力系数略有增大。对于攻角处于升力系数非线性增长区域范围内,湍流强度的增大导致翼型壁面最大负压值增大。当湍流强度变化时,其壁面上出现层流分离泡的位置大小随之发生变化。此外,本文通过流场分析进一步确定了层流分离泡的产生与变化。 相似文献
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研究翼型绕流的转捩预测方法,对于翼型流动细节的精确模拟和气动力的准确计算以及精细化设计均具有十分重要的意义.采用动模态分解(dynamic mode decomposition,DMD)代替线性稳定性理论(linear stability theory,LST)与eN方法结合,不需要求解稳定性方程,成为一种数据驱动的翼型边界层转捩预测新方法,称为DMD/eN方法.在原有方法的基础上,改进了DMD网格线生成方法和扰动放大N因子的积分策略,并将RANS求解器与改进的DMD/eN方法进行耦合,实现了翼型定常绕流转捩预测自动化.采用该方法对LSC72613跨声速自然层流翼型以及NLF0416低速自然层流翼型在不同攻角下的绕流进行转捩预测,转捩点计算结果均与实验值和LST/eN方法吻合良好.该方法计算得到的N值增长曲线与LST/eN方法的包络线也较为吻合,进一步验证了积分策略的正确性.改进的DMD/eN方法可作为自然层流翼型设计的新的有力工具. 相似文献
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This paper describes extensive computer-based analytical studies on the details of unsteady flow behavior around airfoils
subjected to flow induced vibration in turbo-machinery. To consider the time-dependent motions of airfoils, a complete Navier-Stokes
solver incorporating a moving mesh based on an analytic solution of motion equation for airfoil translation and rotation was
applied. The drag and lift coefficients for the cases of stationary airfoils and airfoils subjected to flow induced vibration
were examined. From the numerical results in non-coupling case as out of consideration of the airfoil motion, it was found
that the separation vortex consisted of large-scale rolls with axes in the span direction, and rib substructures with axes
in the stream direction. In the coupling simulation including the airfoil motion, both the translation and the rotation displacement
were gradually increased when the airfoil translation and rotation natural frequencies synchronize exactly with the oscillation
frequency of the fluid force. In addition, the transformation from complex structure with rolls and ribs to two-dimensional
aspect of only rolls could be visualized in three-dimensional simulation. 相似文献
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S.D. Savkar 《Journal of sound and vibration》1976,46(2):195-207
The problem of a thin airfoil oscillating in a transonic flow duct is examined. Asymptotic solutions valid at high frequency are derived which suggest that the degree of interference from the tunnel walls is weaker than would be thought at first. More detailed calculations are then used to deduce the flutter characteristics of such airfoils. It is predicted that the airfoil will suffer a torsional mode instability for a range of parameters. 相似文献
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In this paper, the aerodynamic performance of the S series of wind turbine airfoils with different relative cambers and their modifications is numerically studied to facilitate a greater understanding of the effects of relative camber on the aerodynamic performance improvement of asymmetrical blunt trailing-edge modification. The mathematical expression of the blunt trailing-edge modification profile is established using the cubic spline function, and S812, S816 and S830 airfoils are modified to be asymmetrical blunt trailing-edge airfoils with different thicknesses. The prediction capabilities of two turbulence models, the k-ω SST model and the S-A model, are assessed. It is observed that the k-ω SST model predicts the lift and drag coefficients of S812 airfoil more accurately through comparison with experimental data. The best trailing-edge thickness and thickness distribution ratio are obtained by comparing the aerodynamic performance of the modifications with different trailing-edge thicknesses and distribution ratios. It is, furthermore, investigated that the aerodynamic performance of original airfoils and their modifications with the best thickness of 2% c and distribution ratio being 0:4 so as to analyze the increments of lift and drag coefficients and lift–drag ratio. Results indicate that with the increase of relative camber, there are relatively small differences in the lift coefficient increments of airfoils whose relative cambers are less than 1.81%, and the lift coefficient increment of airfoil with the relative camber more than 1.81% obviously decreases for the angle of attack less than 6.3°. The drag coefficient increment of S830 airfoil is higher than that of S816 airfoil, and those of these two airfoils mainly decrease with the angle of attack. The average lift–drag ratio increment of S816 airfoil with the relative camber of 1.81% at different angles of attack ranging from 0.1° to 20.2° is the largest, closely followed by S812 airfoil. The lift–drag ratio increment of S830 airfoil is negative as the angle of attack exceeds 0.1°. Thus, the airfoil with medium camber is more suited to the asymmetrical blunt trailing-edge modification. 相似文献
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A new experimental set-up is proposed to investigate the noise generated by airfoils. It consists of two adjacent plane jets ducted into an anechoic room, and the airfoils under investigation are placed in the median jet. Besides the benefit in the acoustical conditions of the experiments (decrease of the background noise due to the jets, shift of the preferred frequencies of the jets below the range of interest for the airfoil emission), the aerodynamic situation itself is improved (increase in length of the potential zone, decrease of induced flow fluctuations). There is therefore the possibility to investigate airfoil noise with longer chords and higher incident velocities. 相似文献
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Leading edge noise measurements and calculations have been made on a three airfoils immersed in turbulence. The airfoils included variations in chord, thickness and camber and the measurements encompass integral scale to chord ratios from 9 to 40 percent as well as 4:1 ratios of leading edge radius and airfoil thickness to integral scale. Angle of attack is found to have a strong effect on the airfoil response function but for the most part only a small effect on leading edge noise because of the averaging effect of the isotropic turbulence spectrum. Angle of attack effects can therefore be significant in non-isotropic turbulence and dependent on airfoil shape. It is found that thicker airfoils generate significantly less noise at high frequencies but that this effect is not determined solely by the leading edge radius or overall thickness. Camber effects appear likely to be small. Angle of attack effects on the response function of a strongly cambered airfoil are shown to be centered on zero angle of attack, rather than the zero lift angle of attack. 相似文献
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风力机叶片21%相对厚度翼型粗糙敏感性研究 总被引:4,自引:0,他引:4
基于变速变桨水平轴风力机,依据动量叶素理论和风力机实例,分析得出了叶片外侧翼型(包括21%相对厚度翼型)在低于额定风速变速运行阶段的粗糙敏感性评价指标为升力系数和升阻比的下降率;提出了根据升、阻力系数对输出功率的作用大小来确定两粗糙敏感性评价指标权重系数的方法,并用实例演示了21%相对厚度翼型粗糙敏感性评判基准的获得;另外,通过正交设计、XFOIL软件几何造型与气动计算和方差分析得出了翼型各几何参数在不同雷诺数下对粗糙敏感性不同评价指标的影响程度和最优组合是不一样的。本文结论可为不同风况下风力机翼型的设计和粗糙敏感性评价提供参考。 相似文献
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An experimental investigation into the response of an airfoil in turbulence was undertaken and the results are presented in a two part series of papers. The effects of mean loading on the airfoil response are investigated in Part 1 with the likely origins discussed in this paper (Part 2). Unsteady pressure measurements were made on the surface of a NACA 0015 airfoil immersed in grid turbulence (λ/c=13%) for angles of attack α=0-20°. This paper (Part 2) presents the causes of the low-frequency reduction and high-frequency increase observed in measured lift and pressure spectral levels. Scaling lift spectra on the mean lift reveals the increase in lift spectral level for reduced frequencies greater than 10 is closely related to the airfoils mean pressure field. Based on analysis of the chordwise and spanwise pressure correlation length scale, the reduction in lift spectral level at low reduced frequency appears to result from distortion of the inflow by the mean velocity field. A possible model is developed that accurately predicts mean loading effects on lift spectra. This model uses a circular cylinder fit to the airfoil to compute effects of distortion on the inflow turbulence. The distorted inflow velocity spectrum is then used with Amiet's theory to predict the unsteady loading. This model successfully captures the reduction observed in measured lift spectra at low reduced frequencies. Furthermore, it is shown that the angle of attack effects arising from inflow distortion are significant only when the relative scale of the inflow turbulence to airfoil chord is sufficiently small (λ/c=13% for present experiment). 相似文献