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Dynamic response of a stack/cable system subjected to vortex induced vibration
A stack supported by guy wires at four levels experienced large-amplitude oscillations when the wind speed was > 15 m/s. The purpose of this study was to identify the excitation mechanisms and develop appropriate modification to eliminate excessive vibration. The excitation mechanisms were identified from scoping calculations, analytical prediction with a finite-element code, and observation of the stack/wire reponse. The natural frequency of the most critical mode of the stack was predicted to be nearly equal to 2.2 Hz. The calculated fundamental frequencies of the guy wires at the lower two levels were nearly equal to 1.2 Hz. The vortex-shedding frequency at a wind speed of 15 m/s was nearly equal from 2.2 to 4.4 Hz. The fundamental frequncies of the guy wires at the lower two levels were aproximately one-half that of the most critical mode of the stack. The unsteady-flow theory was employed to model a fluid/structure system with vortex-shedding induced vibration of a stack. Numerical calculation agreed well with the observation that stack vibrations was excited by vortex shedding at the lower portion, which was associated with the third mode of the stack. A coupled model of wind-induced vibration of a stack, based on an unsteady-flow theory and non-linear dynamics of heavy elastic suspended cables, was developed in this study. Numerical analysis results for the coupled system agreed well with observations of the original stack/wire response. The excitation mechanisms of the fluid/structure system were identified as a lock-in resonance of the stack by vortex shedding and parametric resonance of the suspended cable by stack at the ends of the cable supports. Wind speed, a fluctuating lift coefficient, cable tension, and damping are key to the parametric resonance of the cables. This parametric resonance may be eliminated by adjusting cable tension to certain values that will change the natural frequency of the cables. Installation of damping ropes on the wires will further reduce wire vibration.
Dynamic response of a stack/cable system subjected to vortex induced vibration
A stack supported by guy wires at four levels experienced large-amplitude oscillations when the wind speed was > 15 m/s. The purpose of this study was to identify the excitation mechanisms and develop appropriate modification to eliminate excessive vibration. The excitation mechanisms were identified from scoping calculations, analytical prediction with a finite-element code, and observation of the stack/wire reponse. The natural frequency of the most critical mode of the stack was predicted to be nearly equal to 2.2 Hz. The calculated fundamental frequencies of the guy wires at the lower two levels were nearly equal to 1.2 Hz. The vortex-shedding frequency at a wind speed of 15 m/s was nearly equal from 2.2 to 4.4 Hz. The fundamental frequncies of the guy wires at the lower two levels were aproximately one-half that of the most critical mode of the stack. The unsteady-flow theory was employed to model a fluid/structure system with vortex-shedding induced vibration of a stack. Numerical calculation agreed well with the observation that stack vibrations was excited by vortex shedding at the lower portion, which was associated with the third mode of the stack. A coupled model of wind-induced vibration of a stack, based on an unsteady-flow theory and non-linear dynamics of heavy elastic suspended cables, was developed in this study. Numerical analysis results for the coupled system agreed well with observations of the original stack/wire response. The excitation mechanisms of the fluid/structure system were identified as a lock-in resonance of the stack by vortex shedding and parametric resonance of the suspended cable by stack at the ends of the cable supports. Wind speed, a fluctuating lift coefficient, cable tension, and damping are key to the parametric resonance of the cables. This parametric resonance may be eliminated by adjusting cable tension to certain values that will change the natural frequency of the cables. Installation of damping ropes on the wires will further reduce wire vibration.
Dynamic response of a stack/cable system subjected to vortex induced vibration
Strukturantwort von einem Stütze/Spanndrahtsystem mit wirbelinduzierten Schwingungen
Cai, Y. (author) / Chen, S.S. (author)
Journal of Sound and Vibration ; 196 ; 337-349
1996
13 Seiten, 11 Bilder, 2 Tabellen, 14 Quellen
Article (Journal)
English
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