Vortex-induced vibrations of a pipe subjected to unsynchronized support motions
In this study, the nonlinear dynamics of a pipe subjected to vortex-induced vibrations and unsynchronized support motions are investigated, considering the phase difference of support motions at two ends of pipe. We first use a wake oscillator model based on the van der Pol equation to describe the vortex-induced force, and validate the induced vibration amplitude of structure against the experimental data. Then, a nonlinear theoretical model representing the dynamic responses of the pipe system at different locations is constructed based on the Hamilton principle and Galerkin discretization. The resulting ordinary differential equations are numerically solved providing multi-mode approximations to the cross-flow amplitude and the lift coefficient. It is shown that the cross-flow amplitude of the pipe around the first lock-in region is significantly affected by the support motions, resulting in a greatly suppressed or increased vibration amplitude of the pipe. Moreover, the bandwidth of support excitation frequency between minimum and maximum vibration amplitudes changes with the phase difference, owing to the transition between aperiodic and periodic responses of pipe. In addition, the effect of geometric nonlinearity on the responses of pipe with support motions is also discussed.
KeywordsVortex-induced vibration Unsynchronized support motions Multi-mode Lock-in Nonlinear dynamics
The authors gratefully acknowledge the supports provided by the National Natural Science Foundation of China (Nos. 11602090, 51609211 and 11622216), Natural Science Foundation of Hubei Province (2017CFB429) and Fundamental Research Funds for the Central Universities, HUST (2017KFYXJJ135).
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