A Prediction Model for Coupled In-Line and Cross-Flow Vortex-Induced Vibration of a Near-Wall Cylinder Suffering Collision

Abstract A model consisting of structure and wake oscillators is built herein to predict coupled in-line and cross-flow vibration of a near-wall cylinder colliding a plane wall. Hydrodynamics, including vortex shedding frequency and time-varying/time-averaged lift/drag coefficients, are modeled by the Reynolds number, thickness of boundary layer and gap (G) between the cylinder and wall according to VIV phenomena, mechanisms and data analysis. Coefficient of restitution as 1 is taken to control the collision with assumption of elastic impact. The model is validated by experimental data, reflecting effects of the wall and collision successfully. When G/D drops from 2 to 1 (D is the diameter of cylinder), the maximum amplitude drops and shifts to a smaller reduced velocity (Ur). Vibration and resonant tend to start (end) at a larger (smaller) Ur, narrowing lock-in regions. Trajectories are symmetric shape-8. When G/D decreases from 1 to 0.35, first in-line peak disappears gradually. Trajectories become asymmetric shape-8 or oval. Collision happens at small G/D, making irregular trajectories and causing symmetric tips in lower parts. With further research on effects of wall proximity and collision to improve the model accuracy and rationality, it can be applied to evaluate the reliability of submarine pipelines suffering VIV.