基于CFD方法的机翼阵风响应研究

通过引入＂网格速度＂方法模拟阵风条件,求解非定常欧拉方程实现了不同展弦比0012平直机翼阵风响应的数值模拟。首先采用该方法对NACA0006翼型迎角阶跃型阵风的气动力响应进行了计算,计算结果与文献结果、理论值吻合良好。进一步对展弦比分别为5、10的0012平直机翼在迎角阶跃型、One-Minus-Cosine型阵风作用下的气动力响应过程进行了模拟分析。研究结果表明,当展弦比增大时,阵风作用下机翼的升力系数响应会增加,机翼翼根部位气动响应幅值大于翼尖部位响应特性。     

薄翼型阵风响应的数值模拟

 采用有限体积法来数值求解非定常Euler和N-S方程，并在非定常计算中通过引入“网格速度”来计入阵风的影响，实现了对刚性薄翼型阵风响应的有效数值模拟。采用该方法来对薄翼型迎角突然增大的阵风、陡边型阵风这两种典型阵风情况下的翼型气动力响应进行了计算，结果表明：计算结果与现有的一些理论结果都符合较好，与文献中计算结果也吻合。同时通过计算也表明厚翼型的阵风响应需根据工况开展进一步的计算分析。     

翼型和机翼阵风响应的数值模拟

采用有限体积法来数值求解非定常Euler和NS方程,并在非定常计算中通过引入"网格速度"来计入阵风的影响,实现了对刚性翼型和机翼阵风响应的有效数值模拟。首先采用该方法来对翼型攻角突然增大的阵风、陡边型阵风这两种典型阵风情况下的翼型气动力响应进行了计算,结果表明:计算结果与现有的一些理论结果都符合较好,与文献中计算结果也吻合,NS方程的计算结果与Euler方程计算结果在变化趋势上是一致的,但具体的数值有差别。最后针对攻角突然增大的阵风,对不同马赫数下不同展弦比平直机翼的阵风响应进行了数值模拟,得出的计算结果与文献中的计算结果一致。     

基于速度分裂法的翼型阵风响应及减缓数值模拟

国内现阶段飞行器阵风响应CFD模拟通常采用网格速度法（FVM）,而近年提出的更为准确的速度分裂法（SVM）目前主要针对刚性飞行器阵风响应分析。本文将SVM拓展至弹性翼型的One-Minus-Cosine阵风响应计算和减缓研究。基于动态网格系统非定常Navier-Stokes方程,将阵风条件下的速度场分解为阵风速度与背景速度的叠加,理论推导出SVM阵风模拟控制方程,结果表明,FVM是SVM忽略源项后的一种近似方法。进一步建立起弹性翼型阵风响应预测的CFD/CSD时域耦合算法和基于俯仰控制的阵风响应减缓数值模拟方法。算例分析了NACA0012刚性及弹性翼型的One-Minus-Cosine阵风响应,计算结果与文献数据一致,在此基础上分析了阵风尺度、黏性和结构弹性对阵风响应的影响。开展了NACA64A010弹性翼型One-Minus-Cosine阵风减缓模拟,结果表明：单一的沉浮速度控制输入量更有利于减缓阵风载荷峰值,而沉浮速度、俯仰角相结合的控制输入量则能同时减缓翼型的沉浮和俯仰运动。本文工作可为三维飞行器阵风响应和减缓研究提供参考。     

阵风响应及减缓的非定常数值模拟

基于网格速度和动网格方法,通过求解非定常N-S方程计算翼型副翼偏转时的阵风减缓响应,研究开环控制律参数和副翼缝隙对阵风减缓效果的影响。对于单个1-cos阵风,随着偏转角度的增大,减缓效果变大;由于粘性的影响,CFD计算得到的升力峰值减小量明显呈非线性的趋势,减缓效果低于准定常线性理论。对于连续sin阵风,通过调整副翼偏转的频率和最大偏转角,升力能达到很好的减缓效果,此时,副翼偏转频率应接近阵风频率,最大偏转角存在一个最优值。在阵风环境下,副翼间隙对升力系数影响不大,而力矩系数增大一倍,间隙会降低副翼偏转对升力的减缓效果。     

基于遗传算法的柔性飞翼布局阵风减缓设计

将飞翼布局飞机的阵风减缓设计转化为多目标优化问题.基于气动伺服弹性稳定裕度修正个体适应度,建立了改进的多目标非支配排序遗传-阵风减缓算法(NSGA-GLA算法).基于无控飞机的阵风响应特性,提出了阵风减缓控制方案.以翼根弯矩、俯仰角速率和舵偏角最小为目标,采用NSGA-GLA算法对控制器增益参数进行了优化.仿真结果表明,所设计的控制器能够有效改善飞机的阵风响应特性,实现阵风减缓.     

阵风载荷减缓系统故障分析

阵风引起的额外载荷会引起飞机结构疲劳,降低结构使用寿命。采用非定常气动力有理函数拟合方法建立时域状态空间下的动力学系统,设计了阵风载荷减缓系统。研究了阵风载荷减缓系统3种典型故障模式(副翼偏转饱和、舵机卡死、副翼偏转延时)的力学建模方法,并对机翼在阵风减缓系统故障模式下的阵风响应进行分析。仿真结果表明,3种故障模式均不利于阵风载荷减缓系统对阵风载荷的减缓,对于一些特定情况,故障模式下的阵风载荷减缓系统不仅不能减缓阵风载荷,还会带来由副翼偏转不当引起的额外负载。     

多控制面机翼阵风减缓主动控制与风洞试验验证

针对某大展弦比多控制面弹性机翼风洞模型,分别从频域和时域进行阵风响应分析和阵风响应减缓控制律设计.采用经典控制理论设计控制律,通过操纵位于0.6和0.8翼展处的内外侧控制面减小由正弦阵风引起的翼尖加速度(WTA).低频段的阵风减缓的数值分析与风洞试验结果均表明:多控制面的阵风减缓效果优于单控制面.当来流速度为14 m/s时,针对频率为2～5 Hz的阵风,采用多控制面得到的WTA减小10%～24%;当来流速度在8～16 m/s时,针对频率为2 Hz的正弦阵风,闭环状态下的翼尖加速度减小10%～40%;结构有限元模型与真实模型存在工程允许的误差导致理论与试验结果存在一定的误差.本文的工作对工程实际中采用阵风减缓技术具有参考价值.     

多舵面大型民机阵风减缓系统设计

提出用多块对称偏转的扰流片和副翼构成飞机的多舵面操作模型,采用开闭环控制相结合的控制方案,并用LQG方法实现控制律的设计和仿真,设计了一种切实可行的民机阵风减缓控制系统.仿真结果表明,所设计的阵风载荷减缓控制器能有效减缓阵风引起的飞机法向过载,实现阵风减缓.     

弹性机翼阵风响应减缓神经-模糊控制律研究及实验分析(英文)

针对一个大展弦比弹性机翼模型设计了两种阵风减缓神经模糊控制律,并对这两种控制律进行了阵风响应的仿真计算和对比分析。对其中较优一种神经模糊控制律进行了正弦阵风下的单舵面控制系统和双舵面控制系统仿真计算和实验分析。结果表明:两种神经模糊控制律都能有效地对随机阵风进行阵风响应减缓,其中,加了修正因子的控制律比普通神经模糊控制律效果更好;加修正因子的神经模糊控制律对不同风速、不同频率下的正弦阵风扰动都有较好的效果;在阵风扰动较大情况下,双舵面控制律比单舵面控制律阵风减缓效果好;阵风减缓控制系统的各仿真结果与实验结果比较吻合,对实际阵风响应减缓控制律设计有较高的参考价值。     

Application of Active Flow Control Technique for Gust Load Alleviation

A new gust load alleviation technique is presented in this paper based on active flow control. Numerical studies are conducted to investigate the beneficial effects on the aerodynamic characteristics of the quasi "Global Hawk" airfoil using arrays of jets during the gust process. Based on unsteady Navier-Stokes equations, the grid-velocity method is introduced to simulate the gust influence, and dynamic response in vertical gust flow perturbation is investigated for the airfoil as well. An unsteady surface transpiration boundary condition is enforced over a user specified portion of the airfoil’s surface to emulate the time dependent velocity boundary conditions. Firstly, after applying this method to simulate typical NACA0006 airfoil gust response to a step change in the angle of attack, it shows that the indicial responses of the airfoil make good agreement with the exact theoretical values and the calculated values in references. Furthermore, gust response characteristic for the quasi "Global Hawk" airfoil is analyzed. Five kinds of flow control techniques are introduced as steady blowing, steady suction, unsteady blowing, unsteady suction and synthetic jets. The physical analysis of the influence on the effects of gust load alleviation is proposed to provide some guidelines for practice. Numerical results have indicated that active flow control technique,as a new technology of gust load alleviation, can affect and suppress the fluid disturbances caused by gust so as to achieve the purpose of gust load alleviation.     

Aeroelastic dynamic response of elastic aircraft with consideration of two-dimensional discrete gust excitation

Design loads generally require a one-dimensional discrete gust profile without consideration of the spanwise effect, and this profile cannot represent the true gust field exactly. For a high aspect ratio aircraft, two-dimensional gusts may cause critical load conditions, and approaches for calculating dynamic responses under two-dimensional discrete gust excitation are rarely presented. In this paper, a spanwise non-uniform vertical discrete gust field is established based on a one-dimensional ‘1-cos’ gust profile in reference to a DARPA proposal, while frequency and hybrid approaches to the dynamic response analysis of flexible aircraft under this two-dimensional gust excitation are presented. Solution techniques have been applied to a high aspect ratio aircraft to assess the different response characteristics with a comparison between one-dimensional and two-dimensional discrete gust field conditions. The results show that the two-dimensional discrete gust model produces a higher bending moment than that of the one-dimensional condition. Therefore, the critical load conditions that are derived from the two-dimensional discrete gust for high aspect ratio aircraft should be seriously considered. According to the analysis, an active control scheme to alleviate the bending loads caused by the two-dimensional gust is designed, and alleviation effects in different gust conditions are compared.     

Theoretical and Experimental Study of Gust Response Alleviation Using Neuro-fuzzy Control Law for a Flexible Wing Model

Two kinds of neuro-fuzzy gust response alleviation control laws are designed for a flexible large-aspect-ratio wing model. Simulations and comparisons of random gust alleviation using the two control laws are performed. Based on the better neuro-fuzzy control law, experiments and simulations of sinusoidal gust alleviation using one-control-surface control system and two-control-surface control system are developed. The investigations show that the two kinds of neuro-fuzzy gust response alleviation control laws can alleviate random gust responses effectively. The neuro-fuzzy gust response alleviation control law including a modifying factor is better than the other one without it. Further, the better one has good effects on the sinusoidal gust alleviation at different frequencies and flow velocities. The two-control-surface control system has better effects on gust response alleviation than the one-control-surface control system when the gust is strong. The simulation results agree well with the experimental results. These results can be usefully referenced to the design of actual gust alleviation control systems.     

FL-13风洞突风发生装置研究

为在 FL-13风洞中开展飞机全模突风响应试验研究,建立研究所需的突风发生装置,进行了突风发生装置的研究。研究中,从大飞机突风试验需求出发,确定了装置的技术指标,通过数值模拟计算,固化了装置技术指标;通过引导性试验和总体方案对比,选定了单电机驱动双飞轮及曲柄连杆方案;通过动力学分析、结构设计与有限元分析、模态分析和疲劳分析,解决了装置共振、刚度增加困难和安装空间受限等问题;通过装置调试与突风流场考核结果表明,研制的 FL-13风洞突风响应试验装置实现了在来流40 m／s 的风速范围内按正弦规律变化产生突风,模型中心处最大突风振幅达到9 m／s。突风流场的成功模拟,标志着 FL-13风洞具备了开展大展弦比飞机突风响应影响试验研究的能力。     

FL-12风洞突风试验装置研制

论述了在FL-12风洞研制的垂直和水平两种突风发生器,两者都是通过电机驱动凸轮、凸轮带动连杆使叶片摆动,改变电机的转速和凸轮的偏心距来产生叶片不同的频率和振幅,同时还介绍了两种突风发生器的优缺点、安装方法以及减振隔振措施。通过突风流场的测量,得出：突风区域内左右和上下位置突风流场变化较小,前后位置突风流场变化规律为离叶片越近,正弦规律越明显,突风流场越纯正;离叶片越远,正弦风速受干扰越大,突风流场越不纯正;正弦突风流场的风速幅值与来流风速、叶片个数、叶片摆动频率和测点距叶片的风洞轴向距离有关,并且都是正相关的关系。最后简要介绍了突风响应及减缓两期试验,试验结果表明：突风发生器能产生均匀的垂直和水平突风流场,突风频率和强度均可满足弹性模型突风试验要求,FL-12风洞具备了突风响应试验研究技术。     

柔性翼微型飞行器水平阵风响应特性实验研究

设计研制了一种飞翼布局的柔性翼和刚性翼微型飞行器,并在风洞中研究了两种微型飞行器在定常风和水平阵风作用下的气动特性,给出了柔性翼和刚性翼微型飞行器气动特性的差别。研究结果表明：不论是在定常风情况下,还是在水平阵风环境下,柔性翼的气动特性要优于刚性翼结构,柔性翼具有延迟失速和缓和阵风影响的能力,有利于稳定飞行。PIV测量结果表明：由于柔性翼的变形使刚性翼和柔性翼翼面上的流态不同,从而使微型飞行器的气动特性发生改变。