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As an essential component in the offshore oil and gas industry, subsea jumpers are likely to encounter the cyclic-induced stresses caused by the alternating movement of gas plugs and liquid slugs while transporting a multiphase mixture. The present study investigates the gas-liquid flow and the induced vibration in a multi-plane jumper by adopting experimental and numerical techniques. The flow patterns at every characteristic section of a Z-shaped jumper with an inner diameter of 48 mm are experimentally investigated, including dispersed bubbly, slug, churn, wavy, stratified and annular flows. Displacement and pressure sensors are installed near each elbow to record the vibration and pressure response of the jumper. It is found that both pressure characteristics and vibration amplitudes are highly related to the gas content rate, mixing velocity, and gas and liquid superficial velocity. The one-way fluid–solid coupling numerical simulations are performed and validated against the experimental data in terms of the flow patterns and the induced vibrations at different gas–liquid velocities. The results reveal that both simulated flow patterns and vibration responses agree well with the experiments.

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The subsea jumper has become an essential part of subsea production systems as a gas–liquid mixing pipeline connecting the pipeline end manifold (PLEM) to the Christmas tree. During oil and gas transportation, as a common flow pattern, the alternating flow characteristics of the slug flow easily cause pipeline vibration, resulting in pipeline instability or fatigue damage. The present study investigates experimentally and numerically the slug flow characteristics in the subsea M-shaped jumper and its induced vibrations of the jumper. The flow pattern evolution and slug characteristics of the inner slug flow under different gas–liquid velocities are obtained: the slug frequency and slug velocity, as well as the pressure fluctuation and vibration characteristics caused by the slug flow. The results show that the pressure fluctuations in the front and rear parts of the M-type jumper are obviously different. With the increase in the air–water mixing, the two characteristics, the slug frequency, and the slug velocity also increase. The gas velocity has a greater influence on the slug frequency than the liquid velocity. The slug length decreases as the slug frequency increases. Furthermore, numerical simulations under various experimental conditions are carried out. The results show that the simulation results of the pressure data, the slug characteristics, and the induced vibration amplitude are in good agreement with the experimental data.

In this paper, the nonlinear stiffness of a polyester rope under dynamic loads at different temperatures was experimentally investigated. The effects and evolution of the average load, load period and load amplitude on dynamic stiffness were studied. The experimental results show that the dynamic stiffness at 30 °C was greater than that at 20 °C and 40 °C. This is because the dynamic stiffness reduced as the temperature and humidity increased, while in the closed thermostat, humidity decreased with an increase in temperature. In response to this phenomenon, a new set of empirical equations was proposed to consider temperature, humidity, and dynamic load based on the existing empirical formulas, by combining the experimental results. A set of experiments was conducted at 25 °C to verify the accuracy and applicability of the formula. The experimental results and the predicted results are in good agreement.