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实验证明涡流诱发的圆柱体振动有如下特性:存在一严格的振动周期;不管风速如何,振动频率总接近于系统的固有频率;在一定的风速下,振幅大小随风速改变,且达到一最大值;振幅大小与原始的激扰有关。本文提出用Rayleigh自激振方程描述上述的特性。同时借助Van der Pol—近似解法得到极限环θ=R/(e~(-αt)+3/4 β_1/α_1(1-e~(-αt))R~2)~(1/2)当t→∞,自激振幅如下: R_0=V~3(A-BV)~(1/2)这样,本文的这个公式定性地解释了涡流诱发的振动现象。
Experiments show that vortex-induced cylinder vibration has the following characteristics: there is a strict vibration period; regardless of wind speed, the vibration frequency is always close to the natural frequency of the system; at a certain wind speed, the amplitude changes with the wind speed and reaches a maximum Value; the magnitude of the amplitude is related to the original disturbance. In this paper, the Rayleigh self-excited equation is used to describe the above characteristics. At the same time, the limit cycle θ = R / (e ~ (-αt) +3/4 β_1 / α_1 (1-e ~ (-αt)) R ~ 2) ~ (1/2) t → ∞, the amplitude of self-excitation is as follows: R_0 = V ~ 3 (A-BV) ~ (1/2) In this way, the formula of this paper qualitatively explains the vortex-induced vibration phenomenon.