民用飞机低速大迎角抖振流动数值分析

Numerical analysis of buffet flow for civil aircraft at low speed and high angle of attack

关键词:  抖振  大迎角  流动分离  RANS-LES混合方法  应力混合涡流模拟

Key words:  buffet  high angle of attack  flow separation  hybrid RANS-LES method  stress-blended eddy simulation

摘要:

为探究民用飞机低速大迎角下平尾抖振流动特征和机理,基于应力混合涡流模拟方法,对典型民用飞机构型在流动分离状态下开展了高精度流动仿真研究。首先,以NACA 0015翼型大迎角分离流动仿真为例,验证了数值方法对分离流动的解析能力。其次,针对某型民机干净构型开展数值模拟,并与风洞试验数据进行对比。对比分析显示,数值计算得到的平尾平均压强系数和脉动压强系数在不同流动状态下均与风洞试验值吻合良好,且随迎角的变化趋势一致,验证了该方法对机翼分离流动干扰下的平尾流场仿真适用性。最后,基于仿真结果与试验数据的对比,深入分析了机翼分离流动对平尾气动干扰的机理及演化规律。分析结果表明:在抖振边界附近,机翼局部流动分离仅引起平尾较小幅度的抖振载荷；随着迎角进一步增大,强烈的机翼尾迹分离涡逐渐主导平尾流场,导致平尾抖振载荷显著增大。而当迎角继续增大,平尾逐渐脱离机翼尾迹影响区域,抖振载荷幅值增长放缓,此时平尾流场转由其自身的大迎角分离流动主导,并伴随流动主频向高频迁移。本研究揭示了机翼大迎角分离流动影响下平尾抖振载荷特征的演化规律,为民用飞机安全性能评估与设计提供指导。

Abstract:

To investigate the horizontal tail buffet flow characteristics and mechanisms for civil aircraft at low speeds and high angles of attack (AOA), this study conducted high-precision flow simulations for a typical civil aircraft configuration under flow separation conditions based on the stress-blended eddy simulation (SBES) method. Firstly, the accuracy of the numerical simulation in resolving separated flow is validated using a NACA 0015 airfoil at high AOAs. Then, numerical simulations were performed for a clean configuration of a civil aircraft and compared with wind tunnel test data. The comparative analysis shows that the numerically predicted mean and fluctuating pressure coefficients on the horizontal tail agree well with the wind tunnel test data under various flow conditions and exhibit consistent variation trends with AOA, thus verifying the methods suitability for simulating the horizontal tail flow field under the interference of wing separation flow. Finally, based on the comparison between the simulation results and experimental data, the mechanism and evolution of aerodynamic interference on the horizontal tail caused by wing separation flow are analyzed in depth. Analysis results reveal that near the buffet boundary, local wing flow separation induces only minor buffet loads on the horizontal tail. As AOA increases, strong wing wake separation vortices gradually dominate the flow field of the horizontal tail, significantly amplifying the buffet loads of the horizontal tail. As the AOA increases further, the horizontal tail gradually moves out of the wing wake region, causing the growth of the buffet load amplitude to slow down. Consequently, the flow field becomes dominated by the horizontal tails own high-AOA separation flow, accompanied by a shift of the dominant flow frequency toward higher frequencies. The study clarifies the evolution of buffet load characteristics of the horizontal tail under the influence of wing separation flow at high AOA, offering guidance for safety assessment and design of civil aircraft.