NUMERICAL STUDY OF RESPONSE PERFORMANCE OF VORTEX-INDUCED VIBRATION ON A FLEXIBLE CYLINDER WITH PINNED-PINNED BOUNDARY CONDITION

Nowadays, the study methods of VIV on long flexible cylinders contain experimental method, computational fluid dynamic method and semi-empirical method. Due to the expensive cost of experimental method and the long computational time of computational fluid dynamics method, a semi-empirical method study based on a wake oscillator model has been conducted to determine the response performance of vortex-induced vibration (VIV) on a long flexible cylinder with pinned-pinned ends under linearly sheared currents. The coupled model of the structural oscillator of a flexible cylinder and wake oscillator is established, and then the model is discretized and solved based on a standard central finite difference method of the second order. The VIV response characteristics including vibration wavelength, vibration frequency, vibration displacement and frequency varied with time at different shear parameters are compared. The numerical results show that the VIV response is composed of standing wave response and travelling wave response. For a cylinder with small dimensionless bending stiffness, the standing wave response is dominated near the ends while the travelling wave response is dominated near the middle part. However, for a cylinder with large dimensionless bending stiffness, the standing wave response is dominated along the entire cylinder span. As the sheared current increases, the vibration wavelength and displacement decrease, however, the vibration frequency and frequency width increase.