Numerical study on the correlation of transonic single-degree-of-freedom flutter and buffet  

作　　者：GAO ChuanQiang ZHANG WeiWei LIU YiLang YE ZhengYin JIANG YueWen 

机构地区：[1]School of Aeronautics, Northwestern Polytechnical University [2]Department of Engineering Science, University of Oxford

出　　处：《Science China(Physics,Mechanics & Astronomy)》2015年第8期67-78,共12页中国科学：物理学、力学、天文学（英文版）

基　　金：supported by the New Century Program for Excellent Talents of Ministry of Education of China(Grant No.NCET-13-0478);National Natural Science Foundation of China(Grant No.11172237)

摘　　要：Transonic single-degree-of-freedom(SDOF) flutter and transonic buffet are the typical and complex aeroelastic phenomena in the transonic flow. In this study, transonic aeroelastic issues of an elastic airfoil are investigated using Unsteady Reynolds-Averaged Navier-Stokes(URANS) equations. The airfoil is free to vibrate in SDOF of pitching. It is found that, the coupling system may be unstable and SDOF self-excited pitching oscillations occur in pre-buffet flow condition, where the free-stream angle of attack(AOA) is lower than the buffet onset of a stationary airfoil. In the theory of classical aeroelasticity, this unstable phenomenon is defined as flutter. However, this transonic SDOF flutter is closely related to transonic buffet(unstable aerodynamic models) due to the following reasons. Firstly, the SDOF flutter occurs only when the free-stream AOA of the spring suspended airfoil is slightly lower than that of buffet onset, and the ratio of the structural characteristic frequency to the buffet frequency is within a limited range. Secondly, the response characteristics show a high correlation between the SDOF flutter and buffet. A similar "lock-in" phenomenon exists, when the coupling frequency follows the structural characteristic frequency. Finally, there is no sudden change of the response characteristics in the vicinity of buffet onset, that is, the curve of response amplitude with the free-stream AOA is nearly smooth. Therefore, transonic SDOF flutter is often interwoven with transonic buffet and shows some complex characteristics of response, which is different from the traditional flutter.Transonic single-degree-of-freedom （SDOF） flutter and transonic buffet are the typical and complex aeroelastic phenomena in the transonic flow. In this study, transonic aeroelastic issues of an elastic airfoil are investigated using Unsteady Reyn- olds-Averaged Navier-Stokes （URANS） equations. The airfoil is free to vibrate in SDOF of pitching. It is found that, the cou- pling system may be unstable and SDOF self-excited pitching oscillations occur in pre-buffet flow condition, where the free-stream angle of attack （AOA） is lower than the buffet onset of a stationary airfoil. In the theory of classical aeroelasticity, this unstable phenomenon is defined as flutter. However, this transonic SDOF flutter is closely related to transonic buffet （un- stable aerodynamic models） due to the following reasons. Firstly, the SDOF flutter occurs only when the free-stream AOA of the spring suspended airfoil is slightly lower than that of buffet onset, and the ratio of the structural characteristic frequency to the buffet frequency is within a limited range. Secondly, the response characteristics show a high correlation between the SDOF flutter and buffet. A similar ＂lock-in＂ phenomenon exists, when the coupling frequency follows the structural charac- teristic frequency. Finally, there is no sudden change of the response characteristics in the vicinity of buffet onset, that is, the curve of response amplitude with the free-stream AOA is nearly smooth. Therefore, transonic SDOF flutter is often interwoven with transonic buffet and shows some complex characteristics of response, which is different from the traditional flutter.

关 键 词：transonic flow single-degree-of-freedom flutter transonic buffet buffet onset correlation 

分 类 号：O354.2[理学—流体力学]