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海洋平台立管绕流减阻方法研究

作者:润色论文网  来源:www.runselw.com  发布时间:2019/10/26 14:25:22  

摘要:海洋平台立管在服役工作期间一直暴露在海洋环境中,会受到波浪等恶劣海洋环境的作用。当波浪经过海洋平台立管时,会在它的两侧形成交替脱落的旋涡,该旋涡会在海洋平台立管的水平和垂直方向上产生周期性的流体作用力——升阻力,这会影响海洋平台立管的使用寿命、稳定性和安全性。

因此减小海洋平台立管所受到的升阻力,提高海洋平台立管的使用寿命、稳定性和安全性的研究就显得极为重要。本文采用被动控制法——在海洋平台立管前加干扰柱,来减小海洋平台立管所受到的升阻力。

本文首先较为全面的介绍了国内外海洋平台立管绕流减阻问题的相关研究现状,总结分析了目前国内外减小海洋平台立管升阻力的方法。然后利用ANSYS FLUENT建立计算模型,进行数值造波,对波浪传播过程进行了研究,将数值模拟监测到的波高与理论计算所得到的波高进行了比较,结果吻合良好,验证了本文数值造波的正确性。之后进行了波浪作用下海洋平台立管绕流问题的研究。计算了海洋平台立管绕流升阻力系数,分析了其与水深、波浪参数之间的关系。最后进行了波浪作用下海洋平台立管的绕流减阻方法研究。分别计算了单、双和三干扰柱,不同波高,不同水深,不同间距比条件下,海洋平台立管绕流升阻力系数,将它们进行了比较分析,研究了它们的减阻效果。

结果表明:(1)选择推板式造波方法进行造波,并将数值计算得到的波高与理论计算得到的波高进行了比较,结果吻合良好。(2)当波浪刚传播至海洋平台立管时,其升阻力系数随时间做周期性震荡。同一波浪周期条件下,海洋平台立管绕流最大升阻力系数随着波高的增大而增大;海洋平台立管绕流最大升力系数随着水深的增大而增大;海洋平台立管绕流最大阻力系数随着水深的增大而减小。(3)采用被动控制法——在海洋平台立管前加干扰柱的方法,可以有效的减小海洋平台立管绕流升阻力系数。同等波浪参数及水深条件下,海洋平台立管绕流最大升力系数随着干扰柱的增加而减小;海洋平台立管的最大阻力系数随着干扰柱的增加,先增大后减小。双、三干扰柱时,海洋平台立管绕流最大升力系数相差不大,但与单干扰柱相比减阻明显;双干扰柱时,海洋平台立管绕流最大阻力系数相比于单、三干扰柱时减阻明显。考虑到实际工程应用中干扰柱安装的复杂程度及经济成本,选择双干扰柱进行海洋平台立管绕流减阻。

The offshore platform riser has beenexposed to the Marine environment during its service and will be affected by theadverse Marine environment such as waves. As the waves pass through theoffshore riser, they create alternating vortexes on both sides of the riser.These vortexes generate periodic fluid forces in the horizontal and verticaldirections of the riser, which can affect the service life, stability andsafety of the riser.

Therefore, it is very important to reducethe lifting resistance of offshore platform risers and improve the servicelife, stability and safety of offshore platform risers. In this paper, thepassive control method -- adding interference column in front of the offshoreplatform riser to reduce the riser resistance.

At first, this paper comprehensivelyintroduces the current research status of drag reduction of offshore risersaround the current flow, and summarizes and analyzes the current methods toreduce the riser resistance of offshore risers at home and abroad. Then, acomputational model was established by using FLUENT ANSYS to conduct numericalwave building, and the wave propagation process was studied. The wave heightdetected by numerical simulation was compared with that obtained by theoreticalcalculation, and the results were in good agreement, which verified thecorrectness of numerical wave building in this paper. Then the flow around theriser of offshore platform under wave action is studied. The coefficient ofriser resistance is calculated, and the relationship between riser and waterdepth and wave parameters is analyzed. Finally, the method of drag reductionaround the riser under wave action is studied. In this paper, the dragcoefficients of single, double and triple interference columns with differentwave heights, different water depths and different spacing ratios arecalculated respectively.

The results show that :(1) the push-platewave making method is selected for wave making, and the wave heights obtainedby numerical calculation are compared with those obtained by theoreticalcalculation, and the results are in good agreement. (2) when the wave justpropagates to the riser pipe of the offshore platform, its lifting resistancecoefficient oscillates periodically with time. Under the same wave period, themaximum lift resistance coefficient increases with the increase of wave height.The maximum lift coefficient increases with the increase of water depth. Themaximum drag coefficient decreases with the increase of water depth. (3) themethod of passive control -- adding interference column in front of theoffshore platform riser can effectively reduce the flow resistance coefficientaround the offshore platform riser. Under the same wave parameters and waterdepth conditions, the maximum lift coefficient of the flow around the riserdecreases with the increase of the disturbance column. The maximum dragcoefficient of offshore riser increases first and then decreases with theincrease of disturbance column. In the case of twin and triple interferencecolumns, the maximum lift coefficient of the riser around the offshore platformhas little difference, but the drag reduction is obvious compared with that ofthe single interference column. Compared with single and three interferencecolumns, the maximum drag coefficient of the riser around the offshore platformis obviously reduced. Considering the complexity and economic cost ofinstallation of interference column in practical engineering application, thedouble interference column is selected to reduce the drag around the riser pipeof offshore platform.

关键词:海洋平台立管;造波;消波;升阻力系数;干扰柱

offshore platform riser; wave making; waveabsorbing; lift resistance coefficient; interfere with the column

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