共查询到20条相似文献,搜索用时 125 毫秒
1.
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
2.
机翼后缘噪声是飞机重要的机体噪声源之一。本文基于CFD(Computational Fluid Dynamic)数值模拟和Ffcows Williams-Hall理论,研究应用了一种预测干净机翼后缘气动噪声的方法。采用Menter’s SSTκ-ω湍流模型对翼型和机翼进行N-S方程数值模拟得到后缘附近的湍流特征速度和特征长度,再利用Serhat Hosder的预估方法计算后缘噪声强度级。本文首先计算了NACA0012翼型在7种不同状态的后缘噪声,计算结果与实验值比较,符合很好,从而证明了本文采用的方法的可行性和正确性;然后研究了两个亚音速翼型(NACA 0009,NACA 0012),两个超临界翼型(SC(2)- 0710,SC(2)-0714),EET机翼的不同参数对后缘噪声强度级的影响,得出了对降低后缘噪声有参考意义的结论。 相似文献
3.
4.
翼型升阻比和水轮机空化系数是水轮机叶片翼型的重要指标,以NACA63A-614翼型为研究对象,基于B样条曲线对翼型曲线进行参数化构造,得到拟合精度较高的翼型曲线。以升阻比和水轮机空化系数作为优化目标,利用多目标遗传算法和XFOIL软件展开多工况优化设计。对优化后的翼型与原始翼型在多攻角工况范围内进行动力学特性分析,同时将优化前后翼型建模并进行空化实验。分析实验结果表明,优化后的翼型其升阻比和空化性能均得到明显提升,从而验证了该方法的可行性与准确性。 相似文献
5.
6.
针对传声器位置的离散性和遗传算法二进制的编码特点,本文提出改进的自适应遗传算法,对自适应交叉概率和变异概率作了重新设计,并将本文改进自适应遗传算法和传统标准遗传算法以及文献中提到的改进自适应遗传算法进行了比较,发现本文方法能够快速得到更优的结果。此外,本文提出了随频率变化的主瓣宽度和旁瓣水平折中的适应度函数R3,通过与适应度函数R1和R2的仿真结果对比,发现适应度函数R3能够有效地平衡阵列主瓣宽度和旁瓣水平。最后,本文设计了5臂均匀圆阵和5臂螺旋阵,并与本文随机阵进行仿真实验对比,进一步验证本文方法的有效性和可行性。 相似文献
7.
8.
9.
10.
用二维时域有限差分法计算机翼雷达散射截面 总被引:1,自引:0,他引:1
应用二维时域有限差分(FDTD)程序计算二维翼型NACA0012和金属方柱的双站雷达散射截面,与国内外文献上的结果进行比较,证明该程序的有效性.而后计算二维不同形状机翼的双站雷达散射截面(RCS)和不同后掠角时后掠翼和三角翼的双站RCS,得出不同形状机翼有不同的RCS分布;改变后掠角的大小可以改变机翼的RCS分布.因此,根据设计要求,可以通过选用不同机翼形状或不同大小的后掠角,使飞行器达到RCS减缩. 相似文献
11.
基于遗传算法的光综合孔径圆周阵优化 总被引:2,自引:0,他引:2
从光综合孔径圆周阵列成像的基本原理出发,建立了圆周阵列的优化模型;采用改进的实数编码方法对子孔径阵列位置进行编码,运用遗传算法进行子孔径阵列的优化;以阵列的u-v覆盖点间距最大化及最小冗余度来设计目标函数,实现了8~16个子孔径二维圆周阵的优化排列;分析了二维圆周光综合孔径阵列成像系统的点扩展函数、光学传递函数和衍射成像的基本原理;对优化结果与模拟退火算法的结果进行对比,使用仿真成像程序分析其点扩展函数,并与均匀排布的圆周阵列进行对比。结果表明,采用改进的实数编码的遗传算法可以很好地解决综合孔径阵列优化的问题,相对于模拟退火算法,该方法的计算时间更短,结果更优。 相似文献
12.
针对紫外光通信中传统自适应最小均方(LMS)算法存在的不足,提出了一种新的变步长LMS(VSS-LMS)算法,利用MATLAB仿真验证了该算法的可行性,以TMS320VC5509为核心设计了数字信号处理(DSP)最小化硬件系统和VSS-LMS算法的软件流程,在硬件上实现了传统LMS算法和新的VSS-LMS算法的自适应滤波,并进行了对比分析,结果表明所提出的VSS-LMS算法具有较快的收敛速度和较小的稳态误差,这对紫外光通信接收系统的设计和优化具有一定的参考意义。 相似文献
13.
Particle swarm optimization (PSO) is an evolutionary, easy-to-implement technique to design optical diffraction gratings. Design of reflection and transmission guided-mode resonance (GMR) grating filters using PSO is reported. The spectra of the designed filters are in good agreement with the design targets in a reasonable computation time. Also, filters are designed with a genetic algorithm (GA) and the results obtained by the GA and PSO are compared. 相似文献
14.
15.
16.
In this paper, three shortages: full-enhancement mechanism, invariable texture extraction mechanism, and lack of robust enhancement methods, that are always neglected in some tasks based on texture-based target location for Intelligent Transportation System applications (ITS) are introduced. To cover these shortages, a self-adaptive model for texture-based target location is established. It is mainly composed of self-adaptive enhancement mechanism, self-adaptive texture extraction mechanism, and graying enhancement. Also, feedback evaluation strategy for design of texture extraction modes, needed by self-adaptive texture extraction mechanism, is provided. And then, an algorithm of license plate location is designed to evaluate effectiveness of this model. 338 license plate images from natural scenes were applied to test graying enhancement and self-adaptive location. Results of enhancement experiment indicate that graying enhancement is robust in purposiveness, real-time performance, and empirical parameter independence, simultaneously. Further, Results of location experiment demonstrate that not only a sound algorithm of license plate location with high success rate (96.1%) and low average execution time (52 ms) is given but also the effectiveness of the two self-adaptive mechanisms in the proposed model are validated. 相似文献
17.
通过分析认知无线网络引擎决策, 给出了其数学模型, 并将其转化为一个多目标优化问题, 进而提出一种基于混沌量子克隆的优化求解算法, 并证明了该算法以概率1收敛. 算法采用量子编码, 利用Logistic映射初始化抗体种群, 设计了一种基于混沌扰动的量子变异方案. 最后, 在多载波环境下对算法进行了仿真实验. 结果表明, 与QGA-CE(基于量子遗传算法的认知引擎)算法相比, 本文算法收敛速度较快, 具有较高的目标函数值, 可以对无线参数优化调整, 满足认知引擎的实时性要求. 相似文献
18.
V. Sathi Ch. Ghobadi J. Nourinia 《International Journal of Infrared and Millimeter Waves》2008,29(10):897-905
Circular ring microstrip antennas have several interesting properties that make it attractive in wireless applications. Although
several analysis techniques such as cavity model, generalized transmission line model, Fourier-Hankel transform domain and
the method of matched asymptotic expansion have been studied by researchers, there is no efficient design tool that has been
incorporated with a suitable optimization algorithm. In this paper, the cavity model analysis along with the genetic optimization
algorithm is presented for the design of circular ring microstrip antennas. The method studied here is based on the well-known
cavity model and the optimization of the dimensions and feed point location of the circular ring antenna is performed via
the genetic optimization algorithm, to achieve an acceptable antenna operation around a desired resonance frequency. The antennas
designed by this efficient design procedure were realized experimentally, and the results are compared. In addition, these
results are also compared to the results obtained by the commercial electromagnetic simulation tool, the FEM based software,
HFSS by ANSOFT. 相似文献
19.
In this paper, binary optical elements (BOE’s) are designed for generating Bessel beams at mm- and sub mm- wavelengths. The
design tool is to combine a genetic algorithm (GA) for global optimization with a two-dimension finite-difference time-domain
(2-D FDTD) method for rigorous electromagnetic computation. The design process for converting a normally incident Gaussian
beam into a Bessel beam is described in detail. Numerical results demonstrate that the designed BOE’s can not only successfully
produce arbitrary order Bessel beams, but also have higher diffraction efficiencies when compared with amplitude holograms. 相似文献
20.
Ryuichi Katayama 《Optical Review》2013,20(2):248-253
Wavelength-selective waveplates, which act either identically or differently for plural wavelengths, are useful for optical systems that handle plural wavelengths. However, they cannot be analytically designed because of the complexity of their structure. Genetic algorithm is one of the methods for solving optimization problems and is used for several kinds of optical design (e.g., design of thin films, diffractive optical elements, and lenses). I considered that it is effective for designing wavelength-selective waveplates also and tried to design them using the genetic algorithm for the first time to the best of my knowledge. As a result, four types of wavelength-selective waveplate for three wavelengths (405, 650, and 780 nm) were successfully designed. These waveplates are useful for Blu-ray Disc/Digital Versatile Disc/Compact Disc compatible optical pickups. 相似文献