具有脱体涡的厚度翼绕流计算

本文发展了一种面元法(Panel Method),用以计算具有脱体涡的三元厚度机翼的空气动力。所采用的模型简单、直观,并能适用于具有不同翼型的任意平面形状三元机翼。该方法采用了平面四边形网格及由一个平行四边形和四个不共面的三角形组成的网格。在每一网格上布置了二次偶极子面分布,以确保较高的精确度。算例有矩形翼、后掠翼等。计算结果和可以找到的实硷数据及其它的理论方法做了比较,相互吻合是满意的。     

全机亚,超音速侧滑气动特性数值计算

本文给出了用面元法计算亚、超音速流中全机侧滑气动特性的方法。将飞机外形表面分成大量的面元。机身表面上的每个面元含有一个常值源分布，机翼和尾翼弦平面上的每个面元含有一个常值涡分布和一个线性变化的源分布。涡分布和源分布的强度用在控制点处满足法向元穿透速度的边界条件确定。因为不需要侧缘平行于自由流方向，所以对同样的飞机在考虑的所有侧滑角下仅需要一级面元。假设尾涡不偏转，在尾涡面上布置附加的常值涡分布，以     

升力面尾涡卷起的地面效应

本文就二维平板从理论上证明了改进涡格法的超收敛性。用该方法研究了近地升力面尾涡卷起的地面效应。尾涡面上的自由线涡方向应与当地流线方向一致,通过迭代满足这一非线性边界条件的确定尾涡的形状。地面效应以镜象涡系模拟。一系列计算结果表明迭代迅速收敛。本文讨论了升力面距地高度对尾涡位置和形状的影响,计算表明当该高度小于一定距离后,尾涡呈现不稳定。     

基于数值模拟的飞机近场尾涡特征参数计算

尾流间隔是飞机起降和飞行过程的安全保障。近场尾涡特征参数是尾涡远场演变和消散研究的基础，是缩减尾流间隔以提升机场及空域容量的理论依据。采用雷诺平均法数值模拟A320飞机尾涡的近场演化过程，对近场尾涡特征参数的计算方法进行了研究。结果表明：与Hallock-Burnham模型相比，Lamb-Oseen模型能更准确地描述近场尾涡速度分布；采用平均椭圆法计算的近场尾涡涡核半径比采用传统方法计算的精度更高；数值模拟中，A320机型更适合采用3～12 m的平均环量值来描述近场尾涡强度。     

模拟厚度翼型非定常运动的涡方法

本文研究二维厚度翼型的大攻角非定常运动。用沿翼型表面分布的源和面涡来模拟翼型的厚度效应和升力效应,应用离散涡方法模拟前缘分离涡层和尾涡层。计算了大攻角翼型作俯仰运动的情形,与实验结果符合较好。     

计算跨声速机翼尾涡流自适应区域方法

本文利用自适应区域方法调节机翼后每个Ｔｒｅｆｆｔｚ平面上的计算域，使得尾涡对这个计算域边界的影响足够小，从而提高了计算的精度和时间。考虑到间断面的影响，在尾涡面上引入有旋项对流场进行计算。椭圆载荷机翼计算表明本文计算结果与经典Ｂｅｔｚ理论一致。用本文方法对某轰炸机进行了计算，计算结果已用于预计其实际飞行的尾涡面。     

基于四叉树网格下的浸入边界-格子Boltzmann方法

提出了一种基于非均匀四叉树网格下的浸入边界-格子Boltzmann方法.在不同层网格界面上,为了保证物理量的连续性,需要在时空方向上进行插值.由于四叉树同层网格在空间上步长相等、且相邻时间层上时间步长相等,所以在时空方向上采用平均值插值,这样做的优点是时空方向插值既可以达到二阶精度,又可以简化计算过程,节省资源,对任意边界加密下的网格,格子Boltzmann方法的实现比较容易.为了充分利用均匀笛卡尔网格的优势,物面边界的处理采用了速度修正法,与传统浸入边界-格子Boltzmann方法中的直接力法、动量交换法相比,无滑移边界条件得到了较好的保证.同时,把大涡模型加入到浸入边界-格子Boltzmann方法中,实现了在四叉树网格数据结构、边界处理技术、大涡模拟几种模型相结合下,绕障碍物的较大雷诺数流动的模拟.通过不可压缩粘性流中圆柱绕流算例验证,结果与其它方法结果吻合良好.     

地面效应对尾涡消散的影响研究

采用大涡模拟方法可以分析和计算近地阶段尾涡消散和运动规律,但模型繁琐、计算复杂。本研究基于镜像涡方法建立了形式相对简单、计算迅速的近地尾涡运动模型和消散模型,计算结果与激光雷达测量数据和大涡模拟数据的偏差都不超过5％,满足动态尾涡间隔研究的需要。     

柔性扑翼非定常涡格法气动计算的改进与实现

旨在快速、准确地模拟微型扑翼飞行器(Flapping-wing MAV)周边流场,根据柔性扑翼的扑动特点,提出了微型飞行器(MAV)气动力计算的一种改进非定常涡格法(UVLM)模型,该模型中充分考虑机翼的瞬时柔性变形、诱导阻力、尾迹涡环畸变以及黏性耗散等因素对气动力的影响;给出了该模型的一个可视化实现,并通过实例验证了该模型的可行性和有效性。算法仿真表明,采用该模型可使平均升力和平均推力计算精度分别提高20%和70%左右。为了提高运算效率,还研究了剔除尾涡对UVLM性能的影响,计算结果显示,剔除距翼面适当距离处的尾涡后,可在保证算法计算精度基本不下降的前提下使运行时间减少2/3,这表明改进的UVLM可作为MAV的一种快速气动力估算工具,在MAV的优化中存在显见的应用价值。     

飞机尾涡流场参数的仿真计算方法研究综述

作为缩减尾流间隔、提高运行效率的研究基础,尾涡流场的仿真计算技术是国内外民航空管研究领域的一个研究热点。在飞机尾涡流场的数值模拟方面,介绍了雷诺平均、大涡模拟和分离涡模拟方法在流场数值模拟方面的研究现状及存在问题;在尾涡流场参数的快速仿真计算方面,综述了典型计算模型的特点及存在的主要问题,包括CROW不稳定性、Greene消散模型、APA消散模型、TDAWP消散模型、D2P消散模型和三阶段消散模型等,分析了上述模型的精度与应用情况。最后对国内外研究现状进行了总结分析,提出了该领域未来的研究方向。     

A new non-linear vortex lattice method:Applications to wing aerodynamic optimizations

This paper presents a new non-linear formulation of the classical Vortex Lattice Method (VLM) approach for calculating the aerodynamic properties of lifting surfaces. The method accounts for the effects of viscosity, and due to its low computational cost, it represents a very good tool to perform rapid and accurate wing design and optimization procedures. The mathematical model is constructed by using two-dimensional viscous analyses of the wing span-wise sections, according to strip theory, and then coupling the strip viscous forces with the forces generated by the vortex rings distributed on the wing camber surface, calculated with a fully three-dimensional vortex lifting law. The numerical results obtained with the proposed method are validated with experimental data and show good agreement in predicting both the lift and pitching moment, as well as in predicting the wing drag. The method is applied to modifying the wing of an Unmanned Aerial System to increase its aerodynamic efficiency and to calculate the drag reductions obtained by an upper surface morphing technique for an adaptable regional aircraft wing.     

一种平尾涡流发生器设计和流动控制研究

平尾的气动特性直接影响飞机的飞行安全,基于改善飞机平尾在负攻角下流动特性的应用需求,设计一种涡流发生器,安装在平尾下表面。通过数值模拟方法研究平尾在不安装涡流发生器和安装涡流发生器两种构型下的流动特征和机理,分析飞机在负攻角下的俯仰力矩特性。结果表明：安装涡流发生器的平尾负失速迎角推迟了4°,负攻角下的俯仰力矩拐点推迟了4°左右,拓宽了飞机的飞行边界。     

Investigation of Vortex Interaction in Canard-FSW Configurations Based on the Numerical Wind Tunnel Method

The vortex interference mechanism on low Reynolds number between the canard and main wing of the canard-forward sweep wing (Canard-FSW) configurations is simulated numerically by employing the numerical wind tunnel method. The variations of aerodynamic characteristics of Canard-FSW configurations with different positions of the canard are investigated, finding that the aerodynamic interference and mutual coupling effect between the canard and main wing have made great contributions to the lift and stability characteristics of the whole aircraft. Canard can radically improve the surface flow pattern of the main wing. And its own vortex can have a favorable interference on the main wing and can effectively control the airflow boundary layer separation. At small angles of attack, the aerodynamic characteristics are sensitive to the positions of the canard and the main wing, but at high angles of attack, the aerodynamic performances of the configuration are not only related to the shape of the canard (forward or backward), but also with the size of control force as well as the features of the vortices generated above the main wing and the canard. The different configurations and vortices are illustrated using the velocity vector, streamlines and pressure contours.     

具有离体涡的边条布局的低速气动力数值计算

使用等效集中涡和输入涡来模拟边缘离体涡的涡格法,在本文中应用到边条机翼布局的气动力计算中。在进行边条机翼的“混合流型”的气动力计算时,对边条采用了产生离体涡的计算模式,在主翼上则采用了附着流动的计算模式。使用这种方法,对两组边条布局进行了计算,计算结果与实验数据进行了比较。     

Static aeroelastic analysis of very flexible wings based on non-planar vortex lattice method

A rapid and efficient method for static aeroelastic analysis of a flexible slender wing when considering the structural geometric nonlinearity has been developed in this paper. A non-planar vortex lattice method herein is used to compute the non-planar aerodynamics of flexible wings with large deformation. The finite element method is introduced for structural nonlinear statics analysis. The surface spline method is used for structure/aerodynamics coupling. The static aeroelastic characteristics of the wind tunnel model of a flexible wing are studied by the nonlinear method presented, and the nonlinear method is also evaluated by comparing the results with those obtained from two other methods and the wind tunnel test. The results indicate that the traditional linear method of static aeroelastic analysis is not applicable for cases with large deformation because it produces results that are not realistic. However, the nonlinear methodology, which involves combining the structure finite element method with the non-planar vortex lattice method, could be used to solve the aeroelastic deformation with considerable accuracy, which is in fair agreement with the test results. Moreover, the nonlinear finite element method could consider complex structures. The non-planar vortex lattice method has advantages in both the computational accuracy and efficiency. Consequently, the nonlinear method presented is suitable for the rapid and efficient analysis requirements of engineering practice. It could be used in the preliminary stage and also in the detailed stage of aircraft design.     

Numerical study of aerodynamic characteristics of FSW aircraft with different wing positions under supersonic condition

This paper investigates the influence of forward-swept wing(FSW) positions on the aerodynamic characteristics of aircraft under supersonic condition(Ma = 1.5). The numerical method based on Reynolds-averaged Navier–Stokes(RANS) equations, Spalart–Allmaras(S–A) turbulence model and implicit algorithm is utilized to simulate the flow field of the aircraft. The aerodynamic parameters and flow field structures of the horizontal tail and the whole aircraft are presented. The results demonstrate that the spanwise flow of FSW flows from the wingtip to the wing root, generating an upper wing surface vortex and a trailing edge vortex nearby the wing root.The vortexes generated by FSW have a strong downwash effect on the tail. The lower the vertical position of FSW, the stronger the downwash effect on tail. Therefore, the effective angle of attack of tail becomes smaller. In addition, the lift coefficient, drag coefficient and lift–drag ratio of tail decrease, and the center of pressure of tail moves backward gradually. For the whole aircraft,the lower the vertical position of FSW, the smaller lift, drag and center of pressure coefficients of aircraft. The closer the FSW moves towards tail, the bigger pitching moment and center of pressure coefficients of the whole aircraft, but the lift and drag characteristics of the horizontal tail and the whole aircraft are basically unchanged. The results have potential application for the design of new concept aircraft.     

耦合多螺旋桨滑流影响的低雷诺数机翼设计

以某型手抛式太阳能无人机(UAV)模型为对象进行考虑多螺旋桨滑流影响的低雷诺数机翼平面形状设计研究。首先,基于升力面理论发展了准定常求解多螺旋桨/机翼相互气动干扰问题的涡格法(VLM)程序,并采用建立参考翼型气动特性数据库的形式发展了相关低雷诺数修正(LRC)方法;然后,通过对翼型、低雷诺数机翼及单螺旋桨/机翼算例的数值模拟及与相关实验结果的对比,验证了本文数值方法具备模拟低雷诺数复杂流动问题的可靠性及准确性;最后,对某型手抛式太阳能无人机简化拉力多螺旋桨/机翼模型进行了直接优化设计及反设计,并通过具有较高精度的CFD准定常求解技术对优化结果进行了验证。结果表明:以CFD方法计算结果为参考,本文涡格法程序及低雷诺数修正方法能够准确高效地计算相关低雷诺数复杂流动问题;传统未考虑多螺旋桨滑流影响的设计机翼在实际螺旋桨工作状态下将偏离设计点,机翼气动特性得不到提高;考虑螺旋桨滑流影响的优化设计方法能够有效改善机翼阻力特性,相对应地,在设计状态下优化机翼总阻力能够降低19.52counts。     

垂直起降固定翼无人机的翼尖垂尾设计分析

垂直起降固定翼无人机兼具固定翼飞机速度快、航程远和多旋翼无人机垂直起降、可悬停作业的优点,研究其翼尖垂尾对整机气动特性的影响具有重要意义。垂直起降固定翼无人机采用翼尖下垂尾的设计可以在充当垂尾使用的同时兼具翼尖小翼和起落架的作用。对比下垂尾、上垂尾、翼梢端板和常规布局四种翼尖设计,采用LBM-LES算法、壁面自适应局部涡粘大涡模拟湍流模型对四种设计的气动特性进行仿真模拟分析。结果表明:翼尖下垂尾在平飞状态时比其他三种设计气动效率更高,在垂直起降或悬停状态时,抗侧风稳定性更好。     

后缘喷流对三角翼绕流影响的N-S方程数值分析

本文用拟压缩性方法求解不可压流雷诺平均拟压缩Ｎ－Ｓ方程组,对带有后缘喷流的三角翼粘性绕流进行了数值模拟,求解中采用了Ｂｅａｍ－Ｗａｒｍｉｎｇ隐式近似因子分解格式以及ＭＭＬ代数湍流模型。计算结果说明,后缘喷流使涡核压强降低,使涡核速度增大,从而对三角翼前缘分离涡有稳定作用,并能增大上翼面的负压值和下翼面的正压值,从而可以增加部分升力。计算结果还说明,喷口面积或喷流下偏会使上述作用增强。