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Wind and Structures
  Volume 29, Number 6, December 2019, pages 441-455
DOI: http://dx.doi.org/10.12989/was.2019.29.6.441
 


Vortex induced vibration analysis of a cylinder mounted on a flexible rod
Mehdi Zamanian and Luigi Garibaldi

 
Abstract
    In this study, vortex induced vibrations of a cylinder mounted on a flexible rod are analyzed. This simple configuration represents the key element of new conception bladeless wind turbine (Whitlock 2015). In this study the structure oscillations equation coupled to the wake oscillation equation for this configuration are solved using analytical perturbation method, for the first time. An analytical expression that predicts the lock-in phenomena range of wind speed is derived. The discretized equations of motion are also solved using RKF45 numerical method. The equations of motion are discretized by Galerkin method. Free vibration mode shape of the structure taking into account the discontinuity of the cross section are used as comparison function. Numerical results are compared to the analytical results, and they show a satisfying agreement. The effect of system parameters on the oscillations of structure and wake as well as on the lock-in domain are presented. Moreover, it is shown that the values of wind speed triggering the start and the stop of the lock-in phenomenon, for increasing wind speed are different from those values obtained during the reverse process, i.e., when the wind speed decreases.
 
Key Words
     vortex induced vibration; lock-in; van der Pol wake oscillator; circular cylinder; perturbation method
 
Address
Mehdi Zamanian: Department of Mechanical Engineering, Faculty of Engineering, Kharazmi University, P.O. Box 15719-14911, Tehran, Iran
Luigi Garibaldi: Dipartimento di Ingegneria Meccanica e Aerospaziale, Politecnico di Torino, C.so Duca degli Abruzzi, 24, 10129, Torino, Italy
 

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