突风作用下圆柱结构气动特性的试验研究

突风(平均风速随时间快速变化)作用在结构或构件上时，结构的气动力和振动状态与平稳风作用下的结果有何不同，是值得研究的问题。在风洞实验室，利用电压控制的方法，实现了具有一定风速加速度的突升和突降的风速变化过程，测试了圆柱结构在突变风速平稳风速作用下的气动力和振动状态，试验结果表明：当突升风速作用在模型上时，采用瞬时风速和气动力算得的力系数和在平稳风速下的结果一致；当突降风速作用在模型上时，采用瞬时风速和气动力算得的力系数虽然在大小上和在平稳风速下的结果一致，但是其对应的临界雷诺数范围比平稳风速对应的临界雷诺数范围，整体向小的方向上偏移了一定的量值。当不涉及到临界雷诺数时，本文的突变风速不会激发模型的大幅振动；当风速升至或降至临界雷诺数区域时，模型将发生稳定的大幅振动；当风速经过临界雷诺数时，在临界雷诺数对应的风速下发生大幅振动，随着风速的升高或降低使得对应的雷诺数离开临界区域时，振动逐渐消失

Tests for aerodynamic characteristics of a circular cylinder in unsteady wind

The difference between aerodynamic forces and vibration characteristics of structures in unsteady wind and those in steady wind is a subject worth studying.In boundary layer wind tunnel,increasing wind and decreasing wind were generated with certain wind acceleration using voltage control.Aerodynamic forces and vibration amplitude were measured in both unsteady wind and steady one.Experiment results showed that aerodynamic force coefficients in increasing wind calculated with instantaneous wind velocity and aerodynamic force ones with those in steady wind are almost the same;although values of aerodynamic force coefficients in decreasing wind calculated with instantaneous wind velocity and aerodynamic force ones with those in steady wind are almost the same,the critical Reynolds number range in decreasing wind offsets a certain value and becomes smaller compared with that in steady wind;unsteady wind does not induce large amplitude vibration when its velocity is outside of the critical Reynolds number range;when wind velocity increases or decreases into the critical Reynolds number range,large amplitude vibration occurs;when wind velocity crosses the critical Reynolds number range,large amplitude vibration occurs when the corresponding Reynolds number is in the critical range and vibration disappears when the corresponding Reynolds number departs from the critical range.