大振幅下薄翼和流线型箱梁的气动迟滞研究

回顾了机翼和箱梁的气动迟滞效应研究现状，介绍了大振幅下获取薄翼和流线型箱梁自激气动力的风洞试验。研究结果表明：薄翼在超过失速角的振幅条件下，升力并没有出现明显的失速现象，但气动力的高阶谐波分量显著增加；大振幅条件下，流线型箱梁的气动力高阶谐波分量也比较显著，并以第2和第3阶谐波分量为主。此外，在大振幅条件下，流线型箱梁的气动力矩迟滞曲线可出现“8字环”，即气动力在一个振动周期内既做了正功也做了负功；其中，迟滞曲线“8字环”的气动正功部分随着振幅和折算风速的增大而增加。该现象可导致桥梁也出现类似于失速机翼的极限环震荡。最后，基于不同振幅下流线型箱梁的力矩迟滞曲线，简要讨论了大跨度桥梁在颤振后状态可能出现的振动形式和气动稳定性。

Aerodynamic hysteresis of thin airfoil and streamline box girder under large amplitude oscillation

The state-of-the-art of aerodynamic hysteresis of airfoil and box girder is reviewed briefly. A detailed introduction is given to the wind tunnel tests of motion-induced aerodynamic force measurements of thin airfoil and streamline box girder under large amplitude oscillation. The test results show that the lift stall didn＇t occur while the torsional amplitude exceeds the stall incidence angle, and the higher order harmonic components are remarkable in the aerodynamic force. The aerodynamic hysteresis curve of pitching moment for streamline box girder can take on ＂8-shape＂ loop, which means that the aerodynamic forces can provide both the positive and nega tive works within one vibration period. The limited cycle oscillation may also occur for bridge deck, which is usually observed in the stall airfoil. Based on the aerodynamic hysteresis curve of pitching moment under different amplitudes, the possible vibration pattern and aerodynamic in- stability are discussed for the post-flutter state of long span bridge.