【作者】 杨立芝；

【导师】 高正红；

【作者基本信息】 西北工业大学 ， 飞行器设计， 2004， 博士

【摘要】 大迎角飞行与机动是现代战斗机的重要特征之一,能够准确地模拟大迎角非定常流场结构及预测相应的大迎角非定常气动力特性,对现代战斗机及其控制系统的设计至关重要。本文采用数值计算方法,通过求解三维N-S方程,分别对绕机翼、机翼-机身-鸭翼组合体大迎角流场结构及气动力特性进行数值模拟与分析,得到了良好的数值模拟结果。同时,为了满足飞行器大迎角机动飞行动力学特性研究的需要,本文在对大迎角气动力进行数值模拟的基础上,开展了相应的大迎角动态气动力特性的建模研究。 主要完成了以下几方面的工作: 1 采用数值计算方法,对亚音速三角翼静态纵向及带有小侧滑和横侧小扰动情况下的流场及相应的气动特性进行了计算,利用数值计算所得到的大迎角流动流场数据,根据实验研究结果及流场拓朴理论,建立了用于大迎角旋涡流场结构特性分析的方法。给出了三角翼大迎角情况下相应的气动力、力矩系数,以及机翼前缘分离涡轴线位置和旋涡破裂位置随迎角的变化规律,并对带有小侧滑和横侧小扰动情况下对横侧力矩的影响进行了计算与分析。计算结果表明与实验结果符合较好。 2 采用数值计算方法,对三角翼进行大迎角俯仰机动过程中的动态流场结构进行了计算,分析了俯仰角速度对流场结构和气动力系数的影响。在此基础上,对三角翼在上仰过程中受到横侧小扰动情况下的流场结构和气动力特性进行了计算研究。给出了三角翼纵向动态情况下的气动力系数变化,特别是大迎角横侧力矩系数的变化特征,并对受到横侧小扰动后,可能引发的横侧运动不稳定现象进行了分析。结果表明,机翼的上仰运动延迟了机翼上翼面旋涡的破裂,同时,随着机翼俯仰角速度的提高,机翼抵抗旋涡非对称破裂的能力明显增强,从而使得机翼在运动过程中,抵抗非操纵横侧偏离的能力明显提高。 3 采用数值计算方法,对绕机翼-机身-鸭翼组合体亚音速静态大迎角流场及气动力特性进行了计算。通过计算分析说明,在一定迎角下,前机身涡、边条更多还原

【Abstract】 Current and future fighter airplanes are designed to transiently fly at very high angles of attack and require highly maneuverability. So it is very important to simulate the corresponding flowfield structure and predict the aerodynamics of aircrafts accurately in the designation of modern fighter aircrafts and their control systems. In this paper, three-dimensional Navier-Strokes numerical simulations were carried out to predict the characteristics of the vortex-dominated flowfield over delta wings and a wing-body-canard. Besides, according to state-space model that was proposed by Goman, some research work is developed to simulate the unsteady aerodynamics at high angles of attack. And the corresponding data from Navier-Strokes numerical simulations is used for the identification of the unsteady aerodynamic description. The main work developed in this paper is as follows:1. Numerical investigation of the structure of the vortical flowfield over delta wings at high angles of attack in longitudinal and with small sideslip angle is presented here. The methods that analyze the flowfield structure qualitatively and quantitatively are given by using flowfield data from the computational results. In the region before the vortex breakdown, the vortex axes are approximated as being straight line. As the angle of attack increases, the vortex axes are closer to the root chord, and far away from the wing surface. Along the vortex axes, as the adverse pressure gradients occur, the axial velocity decreases, the vortex becomes unstable, and it is possible to breakdown. The occurrence of the breakdown results in the instability of lateral motion for a delta wing, and the lateral moment diverges after a small disturbance occurs.2. Numerical investigation of the structure of the vortical flowfield over a delta wing undergoing maneuverable motions is presented. Three cases are considered to investigate the frequency effect on the flowfield structure and aerodynamic loads forthe delta wing. The lateral moments are more evident as the frequency decreases at high angles of attack. Pitching motion with high frequency delays the vortex breakdown obviously. Besides, the influences of a transient lateral disturbance on the lateral aerodynamics are researched in the paper. For lower frequency case, the lateral moment diverges even if the disturbance occurs at an angle of attack at which the vortex do not breakdown over the wing. As the frequency increases, the lateral moment has no evident change after the transient lateral disturbance occurs, and the lateral-directional stability is more pronounced.3. The static flowfield over a wing-body-canard is calculated and the vortex flow over the fore-body, strake, canard and wings is analyzed. The influence of the vortex flows on each other is also discussed.4. The dynamic flowfield over the wing-body-canard is calculated and the influence of the reduced frequency on the flowfield and the aerodynamics is analyzed.5. According to the aerodynamic characteristics of aircrafts, the state-space model of unsteady aerodynamics at high angles of attack is established. And the unknown parameters in the aerodynamic model are identified by system identification method. The maximum likelihood method is used as identification principle, and the identified arithmetic is Newton-Raphson method. The results show that the model can describe the unsteady aerodynamics at high angles of attack very well.6. The research about the aerodynamic model establishment is one of the basic research for flight dynamics, the designation of modern fighter aircrafts and their control systems. In this paper, the aerodynamic model method integrates with the numerical simulation to avoid great quantity computations of unsteady aerodynamics. The integration of these two methods is a rather effective, economical and practical method.更多还原