Marine risers transporting unsteady multiphase flows may experience internal flow-induced vibrations depending on several flow-structure parameters. This study presents an experimental investigation of large-amplitude intermittent vibrations of an inclined bendable riser transporting an air-water flow that exhibits an unsteady slug flow pattern. The riser has an initial catenary profile with a length over an internal diameter of about 320. By using a non-intrusive measurement with a high-speed motion capture camera, new insights into the riser dynamic features and slug flow-riser interaction phenomena are presented and discussed in the case of varying gas-to-liquid flow rate ratio (R_GL). Pressure signals are also recorded at the riser inlet and outlet, measuring the pressure fluctuation caused by the hydrostatic change, flow-induced momentum and frictional forces. For a given liquid flow rate or superficial velocity, the inclined bendable riser experiences a modified mean drift of the equilibrium configuration and a greater vibration amplitude when increasing R_GL or the superficial gas velocity. The most critical case has a spatially maximum amplitude of greater than six diameters of the riser pipe. Experimental results of the space-time varying responses and frequencies of the riser are analysed in relation to the associated slug flow features including the slug unit length, translational velocity, frequency and pressure fluctuations. Owing to a coupled slug flow-riser interaction, the liquid slugs and elongated gas bubbles vary spatially and temporally. This entails the highly modulated responses and frequencies, intermittently switching the riser multimodal response, especially when R_GL is greater than two. The amplified bending stresses in the riser are reported, highlighting the critical hydrodynamic effect of unsteady multiphase flow. The characteristic slug frequencies associated with the flexible inclined riser dynamics are also evaluated and compared with those predicted by several empirical correlations in the literature based on stationary, straight and rigid pipes. Overall, experimental observations and data are useful for a numerical model development and comparison towards a practical analysis and design of flexible curved/sagged risers transporting multiphase flows.

输送不稳定多相流的海洋立管可能会经历内部流动引起的振动，具体取决于几个流动结构参数。本研究展示了对输送空气-水流的倾斜可弯曲立管的大振幅间歇振动的实验研究，该空气-水流表现出不稳定的段塞流模式。立管的初始悬链线轮廓长度超过内径约 320。通过使用高速运动捕捉相机的非侵入式测量，提出了对立管动态特征和段塞流-立管相互作用现象的新见解并在气液流量比变化的情况下进行讨论 ( R _GL）。在立管入口和出口处也记录压力信号，测量由流体静力变化、流动引起的动量和摩擦力引起的压力波动。对于给定的液体流速或表观速度，当增加R _GL时，倾斜的可弯曲立管会经历平衡配置的修正平均漂移和更大的振动幅度或表观气体速度。最关键的情况是空间最大振幅大于立管直径的六倍。分析了立管时空变化响应和频率的实验结果，分析了相关的段塞流特征，包括段塞单元长度、平移速度、频率和压力波动。由于耦合的段塞流-立管相互作用，液体段塞和细长气泡在空间和时间上发生变化。这需要高度调制的响应和频率，间歇性地切换立管多模态响应，尤其是当R _GL大于二。报告了立管中放大的弯曲应力，突出了不稳定多相流的临界流体动力学效应。还评估了与柔性倾斜立管动力学相关的特征段塞频率，并与基于固定、直管和刚性管的文献中的几个经验相关性预测的频率进行了比较。总的来说，实验观察和数据对于数值模型的开发和比较是有用的，可用于传输多相流的柔性弯曲/下垂立管的实际分析和设计。