测定颤振导数的机械导纳法

本文通过风洞试验,研究了均匀来流下几种典型节段模型涡激振动对自由衰减法获取颤振导数的影响,提出了克服这种影响的初步方法——机械导纳法。并且在研究涡脱落频率基础上,提出了颤振和涡激振动的区别方法。

THE MEASUREMENT OF FLUTTER DERIVATIVES USING MECHANICAL ADMITTANCE

The present paper, through wind tunnel test, studies vortex-induced vibration's effects on the experimental measurement of flutter derivatives using the Scanlan's method. The results show that torsional flutter derivatives obtained from h/B20.25 rectangular and fairing sections take shape of nonideal, especially from h/B = 1.0 square section. Failures to consider vortex-induced unsteady force or moment and vibration are the main reasons.To reduce these effects, a preliminary method, mechanical admittance is proposed. First, a external force is introduced. It makes the spring-mounted deck sections vibrate sinuously in two-dimensional flow. Secondly, through frequency spectrum analysis, the real spectrum of mechanical admittance function in which vortex-induced force presents only in the form of spectrum can be obtained. The experimental results show flutter derivatives using this method is very closed to the ideal curve, except a slight distorsion near the reduced wind speed of lock-in.In addition, a new method that can be used to distinguish between flutter and vortex-induced vibration is also proposed.