Wind Pressures on End-Cell-Induced Vibrationof Circular Tower

In the case of a circular tower, end-cell-induced vibration (ECIV) occurs at a wind speed a few times higher than the wind speed that induces the vortex-induced vibration. To elucidate the characteristics of the aerodynamic forces due to tip-associated vortices (TAV), which are considered as the cause of ECIV, wind pressures acting on a rigid circular tower were measured in a wind tunnel. The pressure fluctuations due to TAV were detected near the free end of the tower. It is shown that the frequency of fluctuating pressure due to TAV is much lower than that due to the von K?rm?n vortex sheddings and TAV is generated nonalternately. Also, included in this study are numerical analyses using the measured pressures as fluctuating lift forces; the predicted amplitudes of ECIV for a rocking circular cylinder agree with the amplitudes obtained in the wind tunnel experiments. If a thin circular disk is attached to the model top, the amplitudes of ECIV decrease with the increase of the disk diameter. The reason for this phenomenon is clarified.