Effects of yaw-roll coupling ratio on lateral-directional aerodynamic characteristics

Experimental investigation of large amplitude yaw-roll coupled oscillations was conducted in a low-speed wind tunnel using an aircraft configuration model. A special test rig was designed and constructed to provide different coupled motions from low to high angles of attack.A parameter ‘‘coupling ratio" was introduced to indicate the extent of yaw-roll coupling. At each pitch angle, seven coupling ratios were designed to study the yaw-roll coupling effects on the lateraldirectional aerodynamic characteristics systematically. At high angles of attack, the damping characteristics of yawing and rolling moments drastically varied with coupling ratios. In the coupled motions with the rotation taking place about the wind axis, the lateral-directional aerodynamic moments exhibited unsteady characteristics and were different from the ‘‘quasi-steady" results of the rotary balance tests. The calculated results of the traditional aerodynamic derivative method were also compared with the experimental data. At low and very high angles of attack, the aerodynamic derivative method was applicative. However, within a wide range of angles of attack, the calculated results of aerodynamic derivative method were inconsistent with the experimental data, due to the drastic changes of damping characteristics of lateral-directional aerodynamic moments with yaw-roll coupling ratios.     

Dihedral influence on lateral–directional dynamic stability on large aspect ratio tailless flying wing aircraft

The influence of dihedral layout on lateral–directional dynamic stability of the tailless flying wing aircraft is discussed in this paper. A tailless flying wing aircraft with a large aspect ratio is selected as the object of study, and the dihedral angle along the spanwise sections is divided into three segments. The influence of dihedral layouts is studied. Based on the stability derivatives calculated by the vortex lattice method code, the linearized small-disturbance equations of the lateral modes are used to determine the mode dynamic characteristics. By comparing 7056 configurations with different dihedral angle layouts, two groups of stability optimized dihedral layout concepts are created. Flight quality close to Level 2 requirements is achieved in these optimized concepts without any electric stability augmentation system.     

飞行器动态稳定性参数计算方法研究进展

动态稳定性参数（简称动导数）是飞行器控制系统设计、飞行器动不稳定发生边界分析及相应动态稳定性判据研究的关键气动参数。在对飞行稳定性问题进行概述的基础上,介绍飞行器动态稳定性参数数值模拟的国内外研究进展。并按照理论方法、工程近似方法及计算流体力学（CFD）模拟方法的动导数发展方向对近年来主要的动导数计算方法进行了综述,评价了各种动导数预测方法的优缺点,指出了动导数数值模拟在理论基础、非定常气动力建模、预测方法精度和效率等方面存在的问题。最后对动导数数值模拟的发展趋势进行了展望。     

无尾布局后体超声速航向增稳设计方法

针对无尾布局超声速航向静稳定性不足的问题,提出一种基于超声速压缩/膨胀流动的后体超声速航向气动增稳设计方法。首先通过无尾布局扁平后体和常规后体方案航向静稳定性和表面流场差异的对比,明确了后体超声速航向增稳设计思路。然后基于后体参数化外形分析了后体型面对于布局超声速航向静稳定性的影响规律。最后通过评估典型后体方案的综合气动特性验证了后体超声速航向增稳设计方法的可行性。研究表明：重心后侧向投影面积增量、后体脊线以及后体截面曲线是影响后体型面超声速航向增稳能力的3个主要参数。与常规后体型面相比,通过超声速航向增稳设计获得的后体型面能够在布局阻力变化不大的情况下,显著改善无尾布局在跨声速和超声速状态的航向静不稳定性。     

压电网络对叶盘结构气动阻尼的影响

首先通过引入气动影响系数,建立了振动相关气动力与系统振动位移成比例的线性模型。基于此导出了叶盘结构气弹耦合的线性振动方程。接着在叶盘结构中引入压电网络,建立了流 机 电耦合动力学方程;并采用集总参数等效模型研究了压电网络对叶盘结构气动阻尼的影响,对流 机 电耦合系统的特征值问题进行求解,获得了可作为系统气弹稳定性判据的模态气动阻尼比。研究表明,压电网络可以有效改善叶盘结构主要振动形式——节径型振动的气弹稳定性;通过对压电网络中电学参数进行优化设计,可以在较宽范围内提高叶盘结构的颤振边界;压电网络对弯曲振动模态气动阻尼的改善效果优于弯扭耦合振动模态。      

超/高超声速飞行器动态稳定性导数极快速预测方法

飞行器设计早期阶段需要预测大量工况下的动导数。本文发展了一种面向超/高超声速飞行器的动导数极快速预测方法：首先基于当地流活塞理论,将飞行器进行小幅非定常运动所受到的气动力分为受自由来流引起的无附加扰动项以及受物面变形或运动引起的附加扰动项;通过当地表面斜度法、激波后等熵关系求解物面当地流动参数,进而结合非定常运动规律求出飞行器所受非定常气动力;再采用待定系数法对非定常气动力进行提取、辨识,最终得到超/高超声速飞行器动导数。该方法克服了传统方法对CFD流场参数的依赖和耦合,具有极高的计算效率;同时典型算例验证表明,该方法在超声速、高超声速工况下都能够很好预测动导数变化趋势。将该方法应用于复杂外形飞行器动导数预测,并讨论了与CFD方法的误差来源。本文方法可作为高速飞行器总体设计阶段布局选型的工具。     

FM Telemetry for Multiple Force Measurements on Free-Flying Models

The extension of the FM telemetry technique to provide simultaneous measurements of four forces acting on a free-flight aerodynamic model is reported. Developments and procedures required to achieve the accuracy, linearity, and stability necessary for obtaining dynamic stability coefficients are described. System accuracy is believed to be better than 3 percent. Free-flight data, presented in the form of aerodynamic stability derivatives, are in good agreement with measurements taken by conventional methods under the same aerodynamic conditions.     

压气机转子叶片颤振边界的预测方法

通过发展的基于能量法的颤振数值预测方法得到了压气机转子叶片的颤振边界.将计算结构动力学(CSD)分析得到的叶片表面节点位移插值到耦合面的流体网格点上,并将设计的多层动网格技术应用于计算流体动力学(CFD)方法,实现叶栅振荡作用下的非定常分析,得到叶片表面的非定常气动功以及模态气动阻尼比.以某第一级压气机转子叶片为例,对...     

密集编队气动耦合效应分析

简要介绍密集编队飞行时长机旋涡对僚机产生的气动耦合效应，以比奥特－萨瓦尔特定律为基础，初步分析由上洗及侧洗引起的升力、阻力和侧力变化，导出了编队稳定性导数的计算公式，计算及应用举例表明：模型化编队飞行时的气动耦合效应是有实际应用价值的。     

Assessment on critical technologies for conceptual design of blended-wing-body civil aircraft

Civil aviation faces great challenges because of its robust projected future growth and potential adverse environmental effects. The classical Tube-And-Wing(TAW) configuration following the Cayley's design principles has been optimized to the architecture's limit, which can hardly satisfy the further requirements on green aviation. By past decades' investigations the BlendedWing-Body(BWB) concept has emerged as a potential solution, which can simultaneously fulfill metrics of noise, emission and fuel burn. The purpose of the present work is to analyze the developments of critical technologies for BWB conceptual design from a historical perspective of technology progress. It was found that the high aerodynamic efficiency of BWB aircraft can be well scaled by the mean aerodynamic chord and wetted aspect ratio, and should be realized with the trade-offs among stability and control and low-speed performance. The structure concepts of non-cylinder pressurized cabin are of high risks on weight prediction and weight penalty. A static stability criterion is recommended and further clear and adequate criteria are required by the evaluations of flying and handling qualities. The difficulties of propulsion and airframe integration are analyzed. The energy to revenue work ratios of well-developed BWB configurations are compared,which are 31.5% and 40% better than that of TAW, using state-of-art engine technology and future engine technology, respectively. Finally, further study aspects are advocated.