EVOLUTION CHARACTERISTIC AND WORKING MECHANISM ANALYSIS OF ROTATING THIN-WALLED STRUCTURES IN POST-CRITICAL TURBULENT INTERVAL BASED ON FIELD MEASUREMENT

Recent study found that the time-varying characteristic of the load may have a significant effect on the vibrational strength and energy mechanism. The most important structures in fire/nuclear power plants (such as cooling towers, chimneys, etc.) are all typical rotating thin-walled structures. To reveal the vibration evolution characteristic and working mechanism of thin-walled structures in post-critical turbulent interval, the vibration responses of eight typical rotating thin-walled structures of high Reynolds number flow (Re \ge 3.5\times 10^6) are measured. Firstly, non-stationary identifications of signals with different time intervals are performed after depressing and filtering noise. The time-varying mean and extreme estimation of response are studied based on non-stationary analysis model. Besides, the frequency domain evolution characteristics are studied based on evolution spectrum method. On this basis, proportion of resonance component in wind-induced response and its effect are discussed. Then, self-resonant frequency and damping ratio of the structures are identified, and the damping mechanism of different rotating thin-walled structures is studied. The evolution characteristic and working mechanism are revealed as follows. (1) The wind-induced vibration response of the rotating thin-shell structure in post-critical turbulent interval is characterized by stable frequency evolution characteristics and non-stationary evolution characteristics in intensity aspect; (2) The wind-induced vibration problem of rotating thin-walled structures in post-critical turbulent interval should be studied as quasi-static and resonance excitation points separately. The vibration energy distributions of resonance excitation points at different regions of the cooling tower were similar, but the PSD functions of quasi-static points were dramatically different from each other; (3) Vibration energy distribution of the resonant excitation points showed a phased trend, and the proposed resonance spectral expression takes three variation stages of responses into account and achieves high prediction accuracy; (4) With the concept of equivalent damping ratio proposed in this paper, the damping ratio prediction formula is proposed. More importantly, these analysis results show that resonance effects and non-stationary effects on wind-induced effects of rotating thin-walled structures in post-critical turbulent interval are generally notable, and the irrationality of 5% damping ratio value commonly used in the current project for this type of rotating thin-walled structure has been demonstrated.