多段翼型吹气流动分离控制研究

基于雷诺平均Navier-Stokes粘性流动方程,采用数值模拟方法,分析了吹气控制对多段翼型气动性能的影响,阐述了吹气改善多段翼型流动的机理。采用有限体积法对雷诺平均Navier-Stokes方程进行空间离散,时间方向推进采用二阶迎风格式,湍流模型采用SST k-ω模型。结果表明:在多段翼型基础上采取吹气控制可以获得很好的气动增升效果,三段翼型的最大升力系数可达4.98;吹气可改善多段翼型表面流动,减小其流动分离,增加升力;在同样的吹气口几何参数条件下,在一定范围内增大吹气动量系数可以提高多段翼型的升力系数;在多段翼型主翼后段和襟翼同时施加吹气流动控制可以获得更好的效果,升力系数比基本三段翼型(基本构型A)增加30.05%。     

基于混沌多项式方法的层流超临界翼型稳健设计研究

开展层流超临界翼型稳健设计研究。针对传统的基于蒙特卡洛不确定分析方法的稳健设计系统计算量巨大、效率低下等问题,引入了混沌多项式方法,建立了新型稳健设计系统。采用RAE2822翼型稳健设计验证了设计系统的可靠性、高效性。结果表明,混沌多项式方法在保证设计精度的基础上设计效率提高了10倍左右。采用该系统进行了层流超临界翼型稳健设计研究,设计的结果表明:对于层流超临界翼型设计需要兼顾层流区长度、阻力发散特性;基于多目标稳健设计方法可以权衡设计点特性和阻力的波动特性;设计后翼型与原始翼型相比,设计点阻力减小了10cunts,阻力发散马赫数提高了0.01,在整个马赫数范围内维持了低的阻力特性。     

近空间高速飞行器气动特性研究与布局设计优化

高空高速飞行中的黏性干扰效应、真实气体效应和稀薄气体效应成为决定未来空天飞行器能否实现安全飞行、精确控制和制导的重大基础科学问题.介绍了黏性干扰效应、真实气体效应和稀薄气体效应对高空高速飞行器气动特性影响,回顾了飞行器气动布局设计优化的发展过程,给出典型高速高升阻比飞行器气动布局设计及优化的结果.      

Design and optimization of a two-element wing airfoil in a subsonic viscous flow

A numerical and analytical solution of the problem of designing a two-element wing airfoil providing maximum lift-drag ratio in a subsonic viscous flow is presented. In order to bring the theoretical results closer to the facts, viscosity and compressibility are taken into account within the framework of boundary layer theory and the Chaplygin gas model, respectively.     

一种升浮一体环形浮空器气动特性研究

选取填充轻质气体的环形浮空器为研究对象,采用数值模拟方法开展高空风力发电机用浮空器气动特性研究．采用有限体积法求解不可压N-S方程和S-A湍流模型来数值模拟风力机气流场,分别对翼型,安装角,长细比,雷诺数及风力机等因素对引入浮力后浮空器气动特性影响进行研究,对比分析引入浮力后布局外形气动力特性随各外形特征参数的变化规律．数值结果表明,截面翼型弯度越大,最大升阻比越小,出现位置有一定前移;截面厚度越大,三维效应越强,最大升阻比出现有一定的滞后性;增大安装角,相当于增大攻角,使得升力系数和阻力系数随攻角变化曲线均有一定前移;引入浮力后,最大合升阻比增大,并且存在一个明显前移;长细比越小,浮空器升阻比越大,随着长细比增大,浮空器最大升阻比出现越滞后;一定范围内,雷诺数增大,浮空器动升阻比增大,引入浮力后,基于来流风速变化时,浮空器合升阻比随雷诺数增大先迅速减小然后趋于平缓,但基于浮空器尺寸变化时,合升阻比则随雷诺数增大而增大;风轮转速增大,浮空器阻力增大,升力有一定下降．     

跨音速翼型反设计的一种大范围收敛方法

求解跨音速翼型的反设计问题时,传统的梯度型方法一般均为局部收敛. 为增大求解的收敛范围,依据同伦方法的思想,通过构造不动点同伦,将原问题的求解 转化为其同伦函数的求解,并依据拟Sigmoid函数调整同伦参数以提高计算效率,进而构造 出一种具有较高计算效率的大范围收敛反设计方法. 数值算例以RAE2822翼型的表面压力分 布为拟合目标,分别采用B样条方法, PARSEC方法及正交形函数方法等3种不同的 参数化方法,并分别以NACA0012, OAF139及VR15翼型为初始翼型进行迭代计 算. 计算结果证明,该方法适用于多种参数化方法,且具有较好的计算效率,从多 个不同的初始翼型出发,经较少次数迭代后, 均能与目标翼型很好地拟合,是一种高效的大范围收敛方法.     

大展弦比机翼中液压管路的抗大变形设计与优化方法

提出了一种大展弦比机翼管路的抗大变形设计与优化方法。首先建立了大展弦比机翼平板-不同布局管路的装配简化模型;然后分析了在机翼大变形下,管道的弯曲位置、弯曲半径、横向距离、弯曲角度等几种不同布局参数,对管路根部应力、最大应力和卡箍处变形的影响关系。结果表明:弯曲位置与横向距离对应力有较大影响,弯曲位置靠近机翼根部可以降低管道根部应力,但是最大应力显著增加,横向距离的增加可以降低管路根部应力以及最大应力;弯曲位置和弯曲半径对卡箍处变形有较大影响,随着弯曲位置从机翼板根部向变形处移动,卡箍处变形量均先减小后增加,弯曲半径的增加会降低卡箍处变形量。采用遗传算法得到在机翼大变形下最优的管形布局,结果表明,卡箍附近最大应力比直管降低了51%。     

Design and verification of airfoil families for large-size wind turbine blades

For the design of wind turbine blades, the use of a family of specially tailored airfoils is particularly important. The dedicated airfoils can dramatically improve the capability of capturing wind power, reduce the structural weight to save the cost of manufacturing and transportation, and lower the inertial loads as well as the loads due to gust. An overview of the world-wide wind turbine airfoil families developed since 1990's is presented, such as the S series, the DU series, the Risø series, and the FFA series. The design and wind-tunnel tests of the Northwestern Polytechnical University (NPU) airfoil family for megawatt-size wind turbines, called the NPU-WA series, are summarized. All tests for the NPU-WA series are carried out in the NF-3 low-speed wind-tunnel with a two-dimensional (2D) test section of 1.6m×0.8m and at the Reynolds number ranging from 1.6×10⁶ to 5×10⁶. The research activities for further improving the NPU-WA airfoils towards lower roughness sensitivity are also reviewed. The development of the new NPUWA series dedicated for multi-megawatt wind turbines is discussed.     

高升阻比乘波构型优化设计

在M∞ =6, 30km高空条件下,以升阻比为目标函数,进行了锥形流乘波体的黏性优化设计,讨论 了影响乘波体升阻比的因素,并对优化结果进行了数值验证. 结果表明：对于升阻比最大的 黏性优化乘波体,存在最优圆锥角使得源自该基本流场的乘波体升阻比最大;摩阻和波阻处 于同一量级;体积率、细长比和展长比都随着基本流场圆锥角的增大而增大.     

A new direct design method for the medium thickness wind turbine airfoil

The newly developed integral function of airfoil profiles based on Trajkovski conformal transform theory could be used to optimize the profiles for the thin thickness airfoil. However, it is hard to adjust the coefficients of the integral function for the medium thickness airfoil. B-spline curve has an advantage of local adjustment, which makes it to effectively control the airfoil profiles at the trailing edge. Therefore, a new direct design method for the medium thickness wind turbine airfoil based on airfoil integral expression and B-spline curve is presented in this paper. An optimal mathematical model of an airfoil is built. Two new airfoils with similar thickness, based on the new designed method and the original integral method, are designed. According to the comparative analysis, the CQU-A25 airfoil designed based on the new method exhibits better results than that of the CQU-I25 airfoil which is designed based on the original method. It is demonstrated that the new method is feasible to design wind turbine airfoils. Meanwhile, the comparison of the aerodynamic performance for the CQU-A25 airfoil and for the DU91-W2-250 airfoil is studied. Results show that the maximum lift coefficient and the maximum lift/drag ratio of the CQU-A25 airfoil are higher than the ones of DU91-W2-250 airfoil in the same condition. This new airfoil design method would make it possible to design other airfoils with different thicknesses.     

Computation of compressible flows with high density ratio and pressure ratio

The WENO method, RKDG method, RKDG method with original ghost fluid method, and RKDG method with modified ghost fluid method are applied to singlemedium and two-medium air-air, air-liquid compressible flows with high density and pressure ratios： We also provide a numerical comparison and analysis for the above methods. Numerical results show that, compared with the other methods, the RKDG method with modified ghost fluid method can obtain high resolution results and the correct position of the shock, and the computed solutions are converged to the physical solutions as themesh is refined.     

Robust design of natural laminar flow supercritical airfoil by multi-objective evolution method

A transonic, high Reynolds number natural laminar flow airfoil is designed and studied. The γ-θ transition model is combined with the shear stress transport(SST)k-w turbulence model to predict the transition region for a laminar-turbulent boundary layer. The non-uniform free-form deformation(NFFD) method based on the non-uniform rational B-spline(NURBS) basis function is introduced to the airfoil parameterization.The non-dominated sorting genetic algorithm-II(NSGA-II) is used as the search algorithm, and the surrogate model based on the Kriging models is introduced to improve the efficiency of the optimization system. The optimization system is set up based on the above technologies, and the robust design about the uncertainty of the Mach number is carried out for NASA0412 airfoil. The optimized airfoil is analyzed and compared with the original airfoil. The results show that natural laminar flow can be achieved on a supercritical airfoil to improve the aerodynamic characteristic of airfoils.     

Solution of the Inverse Boundary Value Problem of Aerohydrodynamics for a Two-Element Airfoil

The basic inverse boundary value problem of aerohydrodynamics for a two-element airfoil is analytically and numerically solved in the complete formulation. The problems of designing biplane airfoils and an airfoil with a trailing-edge flap or leading edge flap (slat) are solved for a given distribution over the unknown contours of the velocity or the pressure as a function of the contour arc abscissa of the airfoils which depends on a finite number of the parameters.