Wind-induced ovalling oscillations of silo-like, thin circular cylindrical shells have been studied both experimentally and theoretically. Variation of the ovalling characteristics, e.g., amplitude and frequency, with increasing flow were measured using a variety of specimens made of polyester film. The general behavior of the system is characterized by the two specific flow velocities: the threshold and peak flow velocities. On the basis of cross spectral density analysis of the pressure fluctuations acting on a rigid cylinder, an excitation mechanism for the ovalling oscillations is proposed. It was found that the threshold and peak flow velocities predicted by this mechanism agree well with the measured values for higher circumferential modes. The validity of the mechanism is confirmed by the results of an additional experiment on the phase difference between the shell oscillation and the pressure fluctuation. Furthermore, the variation of ovalling amplitude with flow velocity was analyzed by a statistical method with consideration given to the aerodynamic damping associated with the shell-flow interaction. Regarding the odd-numbered circumferential modes, the analytical predictions are constistent with the experimental observations. However, the agreement between the two results is not necessarily good for the even-numbered circumferential modes.
ASJC Scopus subject areas
- Mechanical Engineering