涡激振动作用下大长径比柔性立管内气液两相流型教学实验设计

Teaching experiment design of gas-liquid two-phase flow patterns in a flexible riser with a large aspect ratio subjected to vortex-induced vibration

为提高学生解决复杂工程问题能力,设计了模拟洋流冲击作用的柔性立管内气液两相流型教学实验平台。该平台由相互独立的内流系统和外流系统组成,内流为气液两相流环路,用于模拟海底油气集输系统;外流基于循环水槽搭建,用于模拟海洋环境中水下洋流对立管的冲击。实验中,内流系统的柔性立管置于循环水槽内,受外流的冲击产生涡激振动。采用超声波多普勒流速计、高速摄像机、压差传感器对内、外流场的稳定性进行了测试。实验结果表明,外流冲击引起的涡激振动对管内气液相界面分布规律和流型转变有显著影响,在相同的入口气液流速下,振动模态的增加能够促使流型向高气速区域转变。该平台已应用于“工程流体力学”教学实践。

[Objective]Cultivating an outstanding engineering talent pool that meets the requirements of emerging national strategies has become a key issue that needs to be addressed urgently in higher education.In practice,challenges encountered in engineering often involve multiple complex problems.Facing the new round of technological revolution and industrial transformation,the core of undergraduate engineering education is developing the ability of college students to solve complex engineering problems.Taking the course of engineering fluid mechanics as an example,this study develops high-order fluid dynamics experiments based on the integration of scientific research achievements with fundamentals of fluid mechanics,with an attempt to enhance the student’s ability to solve complex engineering problems.[Methods]Based on scientific research achievements in the multiphase flow of oil,gas,and water in subsea pipelines,an experimental teaching platform of gas-liquid two-phase flow pattern in a flexible riser subjected to vortex-induced vibration was designed and constructed to simulate the impact of ocean currents on the marine riser.The platform consists of two separate internal and external flow systems.The internal flow system is a gas-liquid two-phase flow loop with a flexible riser,which simulates a subsea pipeline that transports oil and gas simultaneously.The external flow system is mainly based on a recirculating water flume,which is used to provide flow currents on the flexible riser.In the experiment,the flexible riser of the internal flow system is placed in the recirculating water flume,which is subject to vortex-induced vibration caused by the external flow.The stability of the experimental platform is tested using ultrasonic Doppler flow meters,high-speed cameras,and pressure differential sensors.As a result of the newly developed experimental teaching platform,the flow regime experiment is upgraded from single-phase flow in static pipe in the gravity field to gas-liquid two-phase flow in a vibrating pipeline in the inertia field.[Results]The experimental results showed that vortex-induced vibration caused by the external flow has a significant impact on the distribution of gas-liquid interface and flow regime transition in the riser.Given the same inlet gas and liquid flow rate,the increase in vibration mode caused the flow pattern transition toward the high gas velocity region.It is shown that the transition of flow regimes depends not only on the Reynolds number but also on the vibration mode of the pipe.Compared with a traditional experiment,which is usually carried out with water flowing in a static horizontal pipe,the new teaching model helps develop the student’s ability to cope with real complex engineering challenges.[Conclusions]Through the integration of science and education,a high-level and innovative experimental teaching model is generated.The new experimental teaching model presented here transforms the latest scientific research progress related to multiphase flow into a part of experimental teaching of engineering fluid mechanics by introducing new scientific research achievements and new content into such teaching.The experimental teaching model developed has been applied in the course of engineering fluid mechanics.Teaching practice indicates that this model can improve the ability of college students to analyze and solve complex engineering problems.The result of this study can also provide a reference for the reform of other engineering courses.