考虑热效应的气动伺服弹性分析方法研究

高速飞行器气动加热效应会影响飞行器结构动力学特性,从而影响飞行器气动伺服弹性(ASE)稳定性,这就是热气动伺服弹性问题。在考虑热效应的飞行器动力学特性分析的基础上,结合非定常气动力分析,提出了一种考虑气动加热效应的飞行器ASE分析方法。结合工程算例,验证了该方法的有效性,并研究了热效应对飞行器ASE稳定性的影响。最后,对飞行器热气动伺服弹性设计提出了一些建议。     

分层剪切湍流大涡模拟的一种动力学亚格子尺度模型

基于Yoshizawa涡粘性模型提出了一种适用于热分层剪切湍流大涡模拟的动力学亚格子尺度 (SGS)模型 ,包括SGS湍流应力和湍流热通量模型 ,计算验证了该模型的正确性 .进一步采用大涡模拟方法和该动力学SGS模型研究了稳定分层和不稳定分层槽道湍流的湍流特性 ,以及湍流主要变量关联量的变化规律 .同时 ,根据计算结果 ,预测了热分层槽道湍流的临界Richardson数 ,与理论分析结果基本相符 .     

超音速探测器-刚性盘-缝-带型降落伞系统的大涡模拟研究

研究了Mach数为2时,流场不同块结构自适应网格加密精度对探测器-刚性盘-缝-带型降落伞系统的气动减速性能以及流场结构特性的影响.对于非定常可压缩流体流动,采用了兼顾激波与湍流的WENO(weighted essentially non-oscillatory)和TCD(tuned center difference)混合计算格式以及拉伸涡亚格子模型的大涡模拟方法.结果表明:在较低的流场块结构自适应网格分辨率下,是难以准确模拟计算降落伞系统重要的气动阻力系数和捕捉流场流动特征细节的.随后验证了流场自适应网格的收敛性.     

大型水平轴风力机叶片气动弹性计算

给出了一种考虑几何非线性的大型风力机静、 动气动弹性一体化计算方法．采用涡尾迹方法进行风力机气动载荷计算．建立风力机风轮的三维壳模型．沿周向平均风力机叶片载荷并加载到结构模型进行非线性静气动弹性分析．基于动力学小扰动假设, 在静平衡构型下进行动力学线性化, 计算风轮固有振动特性．继而结合非定常涡尾迹方法计算风力机动气动弹性响应．计算了NH 1500叶片考虑几何非线性的静气动弹性位移和动气动弹性响应．结果表明,大型风力机叶片几何非线性较为明显地减小静气动弹性位移,同时降低动气动弹性的响应幅值．大型风力机气动弹性响应计算需要考虑几何非线性     

Lagrange中心型守恒格式

提出了Lagrange中心型守恒气体动力学格式．引入了当前时刻子网格密度与当前时刻网格声速产生的网格分片常数压力．初始网格密度乘以初始子网格体积得到子网格质量,这些子网格质量除以当前时刻子网格体积得到当前时刻子网格密度．应用网格分片常数压力,构造了满足动量守恒、总能量守恒的Lagrange中心型守恒气体动力学格式,格点速度以与网格面的数值通量相容的方式计算．对Saltzman活塞问题等进行了数值模拟,数值结果显示Lagrange中心型守恒气体动力学格式的有效性和精确性．     

具有特征提取的小波网络气动力模型

为了使所建气动力模型能准确地刻画飞行器的气动特性,提出一种基于特征提取的小波网络气动力建模方法,通过对横侧向与纵侧向的飞行数据训练样本进行核主成分分析特征,提取出训练样本的基本特征;利用提取的基本特征分别构建横侧向与纵侧向小波网络气动力模型.实验结果表明,提出的集成建模方法预测精度高,用于飞行器的气动力建模是有效的,也是可行的.     

三维可压缩Boltzmann模型及其在低Mach数湍流中的应用

改进了有限差分格子Boltzmann方法(FDLBM),以直接数值模拟气动噪声.基于LB求解器特性,采用动力学方程中的恒定对流速度以实施高阶迎风差分,提高了声波和湍流的分辨率.通过建立一个新的三维粒子模型,计算得到了任意比热容的三维可压缩Navier-Stokes系统.此外,利用Bhatnagar-Gross-Krook (BGK)碰撞算子,通过引入热流量修正,实现了Prandtl数的可变性.在激波管内弱声波以及伴随有温度梯度的Taylor-Couette层流的验证计算中,提出的新方法结果良好.此外也对NACA0012翼型绕流进行了三维模拟.其中,Reynolds数、Mach数和攻角分别取2× 105,8.75×10-2以及9°.计算发现,在机翼前缘附近的分离气流位置,以及表面压力波动强度的Maeh数依赖性方面,数值计算结果与实验结果相吻合.     

直管束流固耦合振动的数值模拟

为了研究反应堆结构中的诸如燃料棒、蒸汽发生器和其它换热器传热管束等的流体-结构交互作用问题,利用有限体积法离散大涡模拟(large eddy simulation, LES)的流体控制方程,用有限元方法求解结构动力学方程,并结合动网格技术,建立三维流体诱发振动的数值模型,模拟直管束中流体的流动及结构振动,实现计算结构动力学(computational structure dynamics, CSD)与计算流体力学(computational fluid dynamics, CFD)之间的联合仿真．首先,基于流固耦合方法对单管的流致振动特性进行了详细分析,得到了其动力学响应与流场特性;其次基于建立的传热管束流致振动计算模型,研究了两并列管、两串列管以及3×3正方形排列管束的流致振动行为．     

三维可压缩Boltzmann模型及其在低Mach数湍流中的应用（英文）

改进了有限差分格子Boltzmann方法(FDLBM),以直接数值模拟气动噪声.基于LB求解器特性,采用动力学方程中的恒定对流速度以实施高阶迎风差分,提高了声波和湍流的分辨率.通过建立一个新的三维粒子模型,计算得到了任意比热容的三维可压缩Navier-Stokes系统.此外,利用Bhatnagar-Gross-Krook(BGK)碰撞算子,通过引入热流量修正,实现了Prandtl数的可变性.在激波管内弱声波以及伴随有温度梯度的Taylor-Couette层流的验证计算中,提出的新方法结果良好.此外也对NACA0012翼型绕流进行了三维模拟.其中,Reynolds数、Mach数和攻角分别取2×105,8.75×10-2以及9°.计算发现,在机翼前缘附近的分离气流位置,以及表面压力波动强度的Mach数依赖性方面,数值计算结果与实验结果相吻合.     

在不均匀旋转大气中瞬时圆形轨道的人造卫星的寿命

本文用能量观点研究了人造卫星在不均匀旋转大气的阻力作用下的寿命.根据流体动力学,大气旋转角速度随高度而减小.大气密度按指数形式而减少.文中推出了卫星在上述旋转大气模型中瞬时圆形轨道上的寿命表达式,并对具体卫星的寿命做了数值估计.结果表明:在本文中所计算出的卫星寿命比前人将大气旋转同地球自转角速度一样的模型所算出的寿命要短些.     

Progresses in application of computational ?uid dynamic methods to large scale wind turbine aerodynamics?

The computational ?uid dynamics (CFD) methods are applied to aerody-namic problems for large scale wind turbines. The progresses including the aerodynamic analyses of wind turbine pro?les, numerical ?ow simulation of wind turbine blades, evalu-ation of aerodynamic performance, and multi-objective blade optimization are discussed. Based on the CFD methods, signi?cant improvements are obtained to predict two/three-dimensional aerodynamic characteristics of wind turbine airfoils and blades, and the vorti-cal structure in their wake ?ows is accurately captured. Combining with a multi-objective genetic algorithm, a 1.5 MW NH-1500 optimized blade is designed with high e?ciency in wind energy conversion.     

湍流度对翼型绕流影响的数值模拟及与实验的对比

研究了NACA0012翼型在低Reynolds数不同湍流度下的空气动力学特性．既运用了有限谱法和QUICK格式相结合的数值计算方法,又通过实验手段,研究了湍流度对流场的影响,并得到了计算与实验相符的结果．计算结果说明了有限谱法的高精度及与其他格式结合后应用的灵活性．对翼型受力和流场的结果分析显示:低湍流度下无明显的失速特征,高湍流度下失速特征明显;湍流度还对边界层后的剪切层有很大影响,高湍流度的受力特征和流场结果与高Reynolds数下的情形相似．     

Computational fluid dynamics based dynamic modeling of parafoil system

The calculation of aerodynamic coefficients has been one of the key issues when modeling parafoil systems, that directly affects model precision. This study relates to investigate limitations of traditional calculation methods. As a result, we achieve aerodynamic parameters of a parafoil using computational fluid dynamics simulations. Also we employ the least square method as a tool for the rapid identification of deflection factors of aerodynamic coefficients. The estimated aerodynamic coefficients of the system were incorporated into the dynamic equations of the parafoil to implement a six degree of freedom model of a parafoil system according to the Kirchhoff equations. Numerical results generated by simulation and airdrop testing demonstrate that the established model can accurately describe the flight characteristics of the parafoil system.     

风力机气动噪声研究现状与发展趋势

首先介绍风力机气动噪声源的基本组成,然后对风力机气动噪声理论预测、实验测试和数值模拟方法进行阐述,重点论述这3类方法在风力机气动噪声研究中的应用现状,并讨论风力机气动噪声抑制技术,最后简要展望风力机气动噪声研究的发展趋势     

RBF Neural Network Based Prediction on Blade Surface Pressure Fields in Compressors北大核心CSCD

The airflow characteristics of the internal flow path of an aero-engine compressor are complex, and the vortex flow field around the blade is characterized by high pressure, high speed, rotation, and unsteadiness. Therefore, there is an urgent need to calculate and predict the aerodynamic characteristics of the complex flow field around the compressor blade efficiently and accurately. The computational fluid dynamics (CFD) method was used to generate the aerodynamic load distribution on the blade surface under different operating conditions for the study of the complex flow fields around aero-engine blades. The radial based function (RBF) neural network was applied to establish the pressure surface aerodynamic load prediction model, and the neural network modeling method was combined with the flow field calculation. The neural network method can learn and train the CFD-based data set to properly compensate the errors from the CFD, which provides a reference for the effective prediction of the complex flow fields around aero-engine compressor blades. © 2023 Editorial Office of Applied Mathematics and Mechanics. All rights reserved.     

Research status and trend of wind turbine aerodynamic noise?

The main components of the wind turbine aerodynamic noise are introduced. A detailed review is given on the theoretical prediction, experimental measurement, and numerical simulation methods of wind turbine noise, with speci?c attention to appli-cations. Furthermore, suppression techniques of wind turbine aerodynamic noise are discussed. The perspective of future research on the wind turbine aerodynamic noise is presented.     

大型近海水平轴风力机转轮的空气动力学性能优化判据

以近海风能工程为研究目标,对具有不同特性参数（设计风速、叶尖线速度和转轮实度）的大容量（1～10 MW）风力机转轮的气动性能与几何特性进行分析与研究．首先提出大型机组转轮气动性能优化判据:在其直径最小的前提下具有尽可能高的年可用风能特性因数以及与之相关的风能利用系数,因而可捕获最多风能,使年发电量最大．接着给出影响它的几个主要气动参数,如转轮设计风速、叶尖线速度以及转轮实度,并分析风力机在近海气象条件下运转时上述两个气动指标随这些参数变化的规律．提供的气动分析方法及结果可作为大型近海风力机转轮气动性能的评价基础．     

Unsteady Flow and its Influence to Aerodynamic and Aeroacoustic of VAWT's

A study is reported of the influence of unsteady flow on the aerodynamics and aeroacoustics of vertical axis wind turbines by numerical simulation. The combination of aerodynamic predictions with a discrete vortex method and aeroacoustic predictions based on Ffowcs Williams-Hawkings equation is used to achieve this goal. The numerical results show that unsteady flow of the turbine has a significant influence on the turbine aerodynamics and can lead to a decrease in generated noise as compared to the conventional horizontal axis wind turbine at the similar aerodynamic performance. (© 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Numerical simulation of unsteady vortex structures in near wake of poorly streamlined bodies on multiprocessor computer system

On the basis of the conservative difference method, spatially unsteady flows near complexly shaped objects are studied. The mathematical model is based on the inviscid gas model. For subsonic, transonic, and supersonic regimes, the nonstationary aerodynamics of various aerospace objects is examined. The three-dimensional structure of the unsteady vortex near wake and its influence on the basic aerodynamic characteristics of aerial vehicles are visualized. The numerical simulation is performed using parallel algorithms on supercomputers of cluster architecture.