Wind-excited ovalling vibration of a thin circular cylindrical shell

Wind-structure interaction simulations of ovalling vibrations in silo groups

“…At first, experiments were conducted to relate the turbulence levels in the flow to the occurrence of ovalling thereby focussing on buffeting mechanisms. Experiments in uniform flows at low speeds (low Re and low turbulence levels of approximately I u = 0.8%) showed that the initiation of ovalling can be very abrupt, meaning that a very small increment in the incident wind velocity could result in a sudden increase of the vibration amplitudes [124,186]. It was also observed that there was a relation between the turbulence length scales in the flow and the wavelengths of the ovalling vibration [124].…”

“…Even straightforward criteria based on resonance effects in the case of vortex shedding and with a goal to determine critical design wind velocities that a structure should be able to withstand, are often inadequate. Buildings might collapse before this critical wind speed is reached [124] because more complex, interactive, aeroelastic effects are causing the vibrations. For the Tacoma Narrows bridge e.g., it was convincingly shown that resonance was not the primary cause of the instability [24] and a complex interplay of different phenomena including aeroelastic, self-excited vibrations are now believed to have caused the collapse [190].…”

“…vortex shedding in the wake of a structure is exclusively considered. The above examples have shown however that a structure might very well collapse long before the wind velocity reaches the design velocity based on such assumptions [124]. It is therefore important to find more general techniques for the prediction of wind-induced vibrations that do not rely on the a priori knowledge of the exact excitation mechanism causing the vibrations but rather take into account all possibly interacting mechanisms at once.…”

“…Ovalling is still an issue today with constructions of ever lighter materials such as liquid-storage tanks and silos [124,255,256]. As pointed out in the introduction (chapter 1), ovalling is also highly relevant during construction phases of such buildings and also for the design of solar updraft towers [169,218].…”

“…Experiments in uniform flows at low speeds (low Re and low turbulence levels of approximately I u = 0.8%) showed that the initiation of ovalling can be very abrupt, meaning that a very small increment in the incident wind velocity could result in a sudden increase of the vibration amplitudes [124,186]. It was also observed that there was a relation between the turbulence length scales in the flow and the wavelengths of the ovalling vibration [124]. In the meantime, an aeroelastic model was proposed by Païdoussis and Wong [186], similar to those used for the study of galloping of bridge decks.…”