计及海底井口影响的隔水管涡激振动响应特性试验

在靠近海底井口位置,隔水管周围流场受井口系统的影响发生变化,流固耦合下涡激振动可能诱发隔水管在横流向(CF方向)更为剧烈的振动。为了研究受管土装置影响的隔水管涡激振动响应特性,使用自主设计的管土装置模拟海底井口,采用8 m柔性立管,进行了均匀流下单管和受管土装置影响的涡激振动对比试验。试验通过FBG光纤应变片测得应变信息,使用模态叠加法、FFT变换处理分析试验数据,对比分析2组隔水管的主导频率、应变时历与幅值谱、无因次振幅以及激励力系数等参数沿管径的分布情况。结果发现管土装置影响下,隔水管主导频率减小;CF方向涡激振动增大,振幅沿径向呈非对称特征;涡激振动振幅更大,隔水管受流场的激励与阻尼更为剧烈。

Experimental study on vortex-induced vibration response characteristics under the influence of the wellhead

At the position beside the deep-water wellhead,the flow field around the riser is changed with affected by the wellhead system.The vortex-induced vibration under fluid-structure interaction may induce more severe vibration of the riser in the cross-flow(CF)direction.In order to study the influence of the riser-soil coupled riser on the riser’s VIV response characteristics,a self-designed riser-soil device is used to simulate the deep-water wellhead.Using 8 m flexible riser,the comparative experiments are done between a single riser and a riser-soil coupled riser about VIV response characteristics.The FBG distribution optical fiber is used to collect the surface strain information of the riser.The test data are analyzed by the modal superposition method and the FFT method.The distribution of the parameters along the riser diameter of the two risers are compared and analyzed,such as the dominant frequency,the strain time history and amplitude spectrum,the dimensionless amplitude and the excitation force coefficient.The results find out that because of the riser-soil coupled riser device,the dominant frequency of the riser is reduced;the vortex-induced vibration of the CF direction is increased,and the amplitude is asymmetric along the riser;the VIV amplitude is larger and the riser is more excited and damped.