### 小振幅振动翼型升力迟滞环变向的成因分析

1. 1. 西北工业大学 航空学院, 西安 710072;
2. 西北工业大学 无人机特种技术重点实验室, 西安 710065
• 收稿日期:2018-09-18 修回日期:2018-10-16 出版日期:2019-05-15 发布日期:2018-12-24
• 通讯作者: 周洲 E-mail:zhouzhou@nwpu.edu.cn
• 基金资助:
装备预研项目（41411020401）；陕西省重点研发计划（2018ZDCXLGY-03-04）；民机专项（MJ-2015-F-009）

### Factors analysis of lift hysteresis loop direction changing for small amplitude oscillating airfoils

XUE Chen1,2, ZHOU Zhou1,2, LI Xu1,2, XU Xiaoping1,2

1. 1. College of Aeronautics, Northwestern Polytechnical University, Xi'an 710072, China;
2. Science and Technology on UAV Laboratory, Northwestern Polytechnical University, Xi'an 710065, China
• Received:2018-09-18 Revised:2018-10-16 Online:2019-05-15 Published:2018-12-24
• Supported by:
Equipment Pre-Research Project (41411020401); Key Research and Development Program of Shannxi Province (2018ZDCXLGY-03-04); Civil Aircraft Specific Project (MJ-2015-F-009)

Abstract: This paper studies the effects of the pivot location and the reduction frequency on the aerodynamic characteristics of the SD7037 airfoil under small amplitude forced oscillation at low Reynolds number. By comparing lift coefficient-time curve with angle of attack-time curve, it is found that the hysteresis loop direction changing of the lift coefficient varies with the angle of attack is mainly due to the change of the phase of the lift coefficient-time curve. It is proved mathematically that the phase is a function of reduction frequency. What's more, when the phase of the lift coefficient-time curve increases, the hysteresis loop of the corresponding lift coefficient-angle of attack curve will change from counterclockwise to clockwise. In this process, the lift coefficient-angle of attack curve inevitably shows a straight line shape, as if the hysteresis phenomenon "disappears". In addition, by comparing the flow field structure, it is found that the pivot location and reduction frequency have different impact on this phase. While the pivot location mainly changes the effective angle of attack of the airfoil, the increase of reduction frequency affects the structure of the surrounding flow field, so that the reaction force brought by the added mass becomes stronger, and thus the lift is improved. Both the forward movement of the pivot location and the increase of reduction frequency will increase the phase of the lift coefficient curve.