Experimental Investigation on Vortex-Induced Vibration of a Flexible Pipe under Higher Mode in an Oscillatory Flow

Abstract

Different from the previous studies of the vortex-induced vibration (VIV) dominated by first mode of flexible pipe in an oscillatory flow, the features of a higher mode dominated are experimentally investigated in the ocean basin. The flexible pipe is forced to harmonically oscillate with different combinations of a period and amplitude. The design dominant mode consists of first and second modes under the maximum reduced velocity (VR) of approximately 5.5 with a KC number ranging from 22 to 165. The VIV responses between only the excited first mode and the excited higher mode are compared and studied using displacement reconstruction and wavelet transform methods. The discrepancies of spatial and temporal response between smaller and larger KC numbers (KC = 56 and 121) are first observed. The strong alternate mode dominance and lock-in phenomena occur in the case of larger KC numbers, while they cannot be observed in the case of smaller KC numbers under higher modes. The VIV dominant frequency in the in-line (IL) direction is found to be always triple the oscillatory flow frequency and not twice that in the cross flow (CF) direction. The dominant frequency in the CF direction can be predicted by the Strouhal law, and the Strouhal number is approximately 0.18 under VR = 5.5, which is not affected by the excited mode. Moreover, differences of response motion trajectory are also revealed in this paper. The present work improves the basic understanding of vessel motion induced VIV and provides helpful references for developing prediction methods of VIV in an oscillatory flow.

Coupling Effects of a Top-Hinged Buoyancy Can on the Vortex-Induced Vibration of a Riser Model in Currents and Waves

“…Taheri et al [18] focused on the interaction between oscillatory flow and cylindrical structures in oblique directions and identified different flow regimes affected by structural vibration through numerical simulation. In contrast to the VIV studies focusing on first-mode-dominated flexible pipes in oscillatory flow, Ren et al [19] investigated the features of a higher-mode-dominated VIV through a model test in the ocean basin. In addition, Neshamar et al [20] and Deng et al [21] elaborated on the vibration trajectories of a flexible cylinder in oscillatory flow, which present certain similarities to those of an elastically mounted rigid cylinder under the same conditions.…”

Experimental Investigation and Numerical Modeling of Two-Phase Flow Development and Flow-Induced Vibration of a Multi-Plane Subsea Jumper

“…(a) (b) Existing studies on the vibration of subsea pipelines mainly focus on in-line planar pipelines and the corresponding vortex-induced vibrations caused by the oscillatory lift force generated by the vortex shedding [17][18][19][20][21][22]. With the development of deepwater oil and gas exploitation technology, the pressure and flow rate in the pipeline gradually increase.…”

“…Studies on multi-planar jumpers were rare, and only a few numerical analyses on internal flow characteristics such as slug flow were carried out by Wang, et al [30], Dai, et al [31], Lu, et al [32], and Song, et al [33]. Nair, et al [34] analyzed the vibration fatigue response of a multi-plane jumper structure for an internal Existing studies on the vibration of subsea pipelines mainly focus on in-line planar pipelines and the corresponding vortex-induced vibrations caused by the oscillatory lift force generated by the vortex shedding [17][18][19][20][21][22]. With the development of deepwater oil and gas exploitation technology, the pressure and flow rate in the pipeline gradually increase.…”