单个柔性旗帜在均匀流中摆动的测力实验

利用自行研制的测力天平在低速风洞中对单个柔性旗帜失稳摆动的受力特性进行了测量，同时还测量了旗帜的振幅、频率等参数。实验结果表明：在实验条件下，宽长比H^＊接近1时，旗帜摆动的扭曲变形可以忽略；影响实验的无量纲参数主要是宽长比H^＊，质量比M^＊和无量纲速度V^＊；保持质量比M^＊不变、改变宽长比H。时，阻力系数C^＊、无量纲振幅A^＊和Sf数都随无量纲速度V^＊线性增大；保持H^＊不变、改变M^＊时，C^＊、A^＊和ST都随V^＊先增大后趋于定值。实验证明，在实验参数范围内旗帜受到的阻力与摆动振幅成正比。估算结果表明忽略惯性力对阻力的贡献对结果影响不大。

Aerodynamic force measurements on a flexible flag flapping in uniform flow

The force characteristic of flexible flags was measured by a self-designed balance in a wind tunnel to investigate the flags＇ flutter instability. Relevant parameters of the flags, such as amplitude, frequency and etc. , were measured in the experiments. In the experiments, when the aspect ratio of the flags is closed to a unit, the distortion of the flags＇ flapping can be ignored. The non-dimensional parameters affecting the experiments are the aspect ratio H＊ , the mass ratio M＊ , and the non-dimensional velocity V＊. Varying the aspect ratio H＊ while keeping the mass ratio M＊ constant, the experimental results show that the drag coefficient CD, non-dimensional amplitude A＊ and St increase linearly with the non-dimensional velocity V＊. Keeping the aspect ratio H~ constant while changing the mass ratio M＊ , the results show that CD, A＊ and St increase with V＊ toward constants. In T：he present experimental conditions, the drag coefficient is proportional to the amplitude. The estimation on the effect of inertia shows the inertia force contributes little to the measurement of drag.