Investigation of coupled response on cylindrical eccentricity induced vibration and flow induced vibration

Abstract

The eccentric vibration and flow induced vibration of the drilling pipe is closely related to the safety of drilling engineering. To reveal the influence of eccentric vibration of the drilling pipe on the flow induced vibration, the effects of the eccentricity on the vibration characteristics of cylindrical flow induced vibrations are emphatically concerned in this paper. Combining the eccentric vibration model and the cylindrical flow induced vibration model, a coupled vibration model is established. The results show that the peak amplitude of the cylinder rises with the increase of the eccentric ratio. The vibration contains both the hydrodynamic frequency and the eccentric frequency, and the eccentric frequency gradually becomes the dominant frequency with the increasing eccentric ratio. The hydrodynamic frequency is locked at 1/2 rotation frequency due to the eccentricity. Eccentricity leads to phase differences in fluid force coefficients and displacements and a weakened correlation between fluid forces and displacements. The wake patterns show a tendency from 2S to P+S and finally to multi-vortex shedding with increasing eccentric ratio, which is the same as the trend of rising amplitude. Both the periodicity of the cylindrical vibrations and the stability of the wake flow decrease with the evolution of the wake flow.