均匀来流中大长径比深海立管涡激振动特性

The VIV characteristics of deep-sea risers with high aspect ratio in a uniform current profile

提出了一种对大长径比深海立管涡激振动特性进行三维耦合数值模拟的方法。其中,流场采用大涡模拟方法进行三维数值模拟,结构振动采用基于薄壳模型的有限元方法进行数值计算,并采用一种将流场和结构响应数据进行实时传输的新方法,实现了流体与固体之间的三维耦合数值模拟。在雷诺数Re=3400和11000下,对某长径比为1200的深海立管模型在均匀来流中的横向涡激振动特性进行了数值模拟与分析。结果表明,大长径比柔性立管的横向振动响应对其尾涡动力特性会产生显著影响,包括会出现涡泄频率显著增大和多频涡泄等复杂现象。尽管来流是均匀的,但立管的横向振动响应会出现明显的多模态特征,除了包含有与涡泄频率一致的振动响应外,还包含有其它频率成分的振动响应。特别地,还会出现多种高阶模态振动共存的非对称复杂弯曲变形等现象。研究表明,该方法为研究深海立管涡激振动特性及其工程预报的相关问题提供了一种有效的途径。

A numerical method using three-dimensional coupling simulations is presented for solving transverse vortex-induced vibration of a deep-sea riser with the high aspect ratio.The three-dimensional flow field is resolved by using a large eddy simulation model and the structure responses are analyzed with the finite element method based on the thin shell model.Such three-dimensional coupling simulations of the fluid-structure interaction on the sea-deep riser are accomplished by use of a novel method with the on-line transmission between fluid dynamics and structure response data.The three-dimensional coupling characteristics of the transverse vortex-induced vibration are numerically simulated and analyzed for a long flexible riser（length to diameter ratio=1200） which is subjected to a uniform current profile（Reynolds number Re=3400 and 11000）.The results show that the vibration responses for such a long riser with the high aspect ratio have remarkable influence on its wake dynamic characteristics,including the remarkable increasing of vortex shedding frequencies and the multi-frequency phenomenon of the vortex shedding.Moreover,despite the inflow current being uniform,the riser is observed to vibrate multi-modally,including not only the vibration responses being consistent with the vortex shedding frequencies,but ones with other frequencies also.In particular,complex bend distortions for such a long riser are observed due to multi-modal vibration responses with high orders.It can be concluded that the present method can be used as an effective tool in analyzing and predicting the VIV characteristics for long deep-sea risers.