考虑辐射阻尼的Spar平台涡激运动分析方法研究

发布时间：2018-05-13 21:03

本文选题：Spar平台 + 涡激运动　；参考：《中国海洋大学》2015年博士论文

【摘要】：随着海洋石油开发逐渐从近海向深水发展,一些用于深水开发的海洋采油平台成为研究的热点,Spar平台是20世纪末才被实际应用到海洋石油开发中的,是较为年轻的一种平台,具有良好的稳定性,便利性,经济性,因此具有广阔的应用前景。而Spar平台在一定来流作用下会发生由于尾流涡旋脱落引起的涡激运动,对立管以及锚泊系统的疲劳寿命有着严重影响,因此,对Spar平台的涡激运动特性进行研究有着重要意义。目前对Spar平台的涡激运动研究以缩尺模型实验居多,但缩尺模型实验中往往选择弗汝德相似准则进行缩尺,从而根据缩尺模型的实验结果外推原型Spar平台的涡激运动特性,这是有所欠缺的,因为引起平台涡激运动的尾流涡旋泄放与雷诺数、约化速度Ur密切相关。在模型实验中如果不能保证比例模型和原型在雷诺数上一致,那么比例模型和原型的振动特性在相似关系上会出现一定程度的不符。尤其对于Spar平台的缩尺模型实验,如果采用弗汝德相似准则进行缩尺实验,由于采用的缩尺比很小,雷诺数在模型和原型之间将发生数量级上的跨越,这对于实验结果的可靠性有着较大影响。因此,本文在第三章着重对缩尺比例模型实验中所采用的相似准则进行了探讨,主要对全相似模型、雷诺相似模型和弗汝德相似模型这三种缩尺模型进行了比较研究,通过数值模拟方法和实验方法最终认为,在涡激振动(涡激运动)的缩尺实验研究中,应首先考虑雷诺相似准则进行缩尺,而通过弗汝德相似准则进行缩尺的模型其振动特性不能与原型满足相应的比例关系。基于Spar平台涡激运动实验研究存在的缺陷,本文在第四章通过MATLAB软件编程对Spar平台的涡激运动进行研究分析。在大多数CFD软件中对涡激振动(涡激运动)的计算并不考虑结构自身速度和加速度对流体反作用力,本文在编程中对该影响进行了考虑,而且目前对于阻尼的计算,往往将结构阻尼和流体阻尼合并为一个阻尼参量,本文将结构阻尼和流体阻尼分开进行计算,建立了考虑辐射阻尼时Spar平台涡激运动的动力模型,比较分析了辐射阻尼对涡激运动的影响,同时对Spar平台横荡,纵荡,横摇和纵摇四个自由度的运动进行耦合求解。为了验证该数值模型的正确性,本文在第五章通过模型实验进行比较分析,此时数值模型采用实际模型实验中的各类参数进行计算,将计算结果同实验结果进行比较,结果表明,此数值模型能较好的符合实际实验情况。本文在第六章对Spar平台的涡激运动进行了数值模拟研究,基于ANSYS-CFX对Spar平台实际尺寸及来流条件下的涡激运动进行了比较分析。通过不同流速下的数值模拟研究发现,尽管Spar平台在水深方向截面尺寸发生变化,但涡旋脱落却有着较强的一致性,并不因截面变化而变化,三维效应明显。另外在第六章本文还运用之前所编译的涡激运动程序进行了数值计算,并将结果同数值模拟的结果进行比较,研究发现,由于编程考虑了辐射阻尼,编程计算所得的纵荡幅值响应较数值模拟结果小得多,而纵荡均值同数值模拟结果能很好吻合,编程计算所得的横荡响应在数值模拟的非锁定区流速下同数值模拟结果能较好的吻合。由于横荡运动足Spar平台涡激运动中最重要的主导运动,可见本文所编译的Spar平台涡激运动的分析程序是有一定适用性的。在第七章本文通过CFD方法对螺旋侧板的抑涡作用进行了机理性研究,建立了带侧板和无侧板的流场数值模型。通过对两种模型的涡旋泄放和升阻力系数的比较分析发现,螺旋侧板的存在能明显降低升力系数幅值,但会增加拖曳力系数均值,螺旋侧板的存在还会对尾流涡泄周期产生影响。通过对带侧板模型不同分段的升阻力系数比较发现,流场模型自上而下有着一致的涡旋脱落周期,而且各分段上的升力系数幅值均大幅减小,并不是叠加后才产生总体升力系数幅值的减小,这和之前很多学者关于螺旋侧板能降低结构整体的升力系数的研究结果并不冲突。本文通过数值编程计算、模型实验和数值模拟这三种方法对Spar平台的涡激运动进行了研究分析,得出了一些较为可靠的结论,对于实际工程应用非常有益。但是由于Spar平台的涡激运动研究在国内外都是比较新的课题,本文还是存在很多方面需要深入研究。
[Abstract]:With the development of offshore oil development from offshore to deep water, some offshore oil extraction platforms used for deep water development have become a hot spot of research. The Spar platform was actually applied to offshore oil development at the end of the twentieth Century. It is a relatively young platform with good stability, convenience and economy, so it has a wide application. The vortex induced vortex shedding motion caused by the wake vortex shedding will occur in the Spar platform, and the fatigue life of the opposing tube and the anchorage system is seriously affected. Therefore, it is of great significance to study the characteristics of the vortex induced motion of the Spar platform. At present, the study of the vortex induced motion of the Spar platform is mostly based on the scale model experiment. However, in the scale model experiment, the Froude similarity criterion is often used to scale the scale, so that the vortex induced motion characteristics of the prototype Spar platform are extrapolated according to the experimental results of the scale model, because the vortex discharge of the wake vortex induced by the platform vortex is closely related to the Reynolds number and the reduction rate of Ur. The proportion model and the prototype are consistent with the Reynolds number, then the vibration characteristics of the proportional model and the prototype will appear to a certain degree of discrepancy. Especially for the scale model experiment of the Spar platform, the Reynolds number is between the model and the prototype, if the scale ratio is very small, if the Froude similarity criterion is used. This will have a great impact on the reliability of the experimental results. Therefore, in the third chapter, the similarity criterion used in the scale scale model experiment is discussed, and the three scale models, such as the fully similar model, the Reynolds similarity model and the Froude similar model, are compared. The numerical simulation method and the experimental method finally think that in the scale experiment of vortex excited vibration (vortex induced motion), the Reynolds similarity criterion should be taken into account first, and the vibration characteristic of the scale model can not satisfy the proportional relationship with the prototype by the Froude similarity criterion. The experimental study on the vortex excitation based on the Spar platform In the fourth chapter, in the fourth chapter, the vortex excited motion of the Spar platform is studied and analyzed. In most CFD software, the calculation of vortex excited vibration (vortex excited motion) does not take into account the reaction force of the structure itself velocity and acceleration. In this paper, the effect is considered in the program, and the current resistance is considered. The structural damping and fluid damping are often combined into a damping parameter. In this paper, the structural damping and fluid damping are calculated separately. The dynamic model of the vortex induced motion of the Spar platform is established in consideration of the radiation damping. The effect of the radiation damping on the vortex excitation is compared and analyzed, and the Spar platform is swaying, sway, rolling and longitudinal. In order to verify the correctness of the four degree of freedom motion, in order to verify the correctness of the numerical model, the fifth chapter is compared and analyzed in the model experiment. At this time, the numerical model is calculated by various parameters in the actual model experiment, and the results are compared with the experimental results. The results show that the numerical model can be better. In the sixth chapter, the numerical simulation of vortex induced motion of Spar platform is studied in this paper. Based on ANSYS-CFX, the actual size of the Spar platform and the vortex excited motion under the flow condition are compared. The numerical simulation study under different flow velocities shows that the Spar platform changes in the depth of the water depth. But the vortex shedding has a strong consistency, it does not change with the cross section, and the three-dimensional effect is obvious. In addition, the numerical calculation is carried out in the sixth chapter, which is compiled before the use of the vortex excited motion program. The results are compared with the numerical simulation results. It is found that the programming calculation results from the programming calculation because of the programming consideration. The amplitude response of the longitudinal amplitudes is much smaller than that of the numerical simulation results, and the mean of the sway is in good agreement with the numerical simulation results. The yaw response obtained by the programming calculation is in good agreement with the numerical simulation results under the numerical simulation of the flow velocity in the unlocked region. The most important leading motion in the vortex motion of the Spar platform of the sway motion can be seen in this paper. The analysis program of the eddy excited motion of the compiled Spar platform has some applicability. In the seventh chapter, the vortex action of the spiral side plate is studied by the CFD method, and the numerical model of the flow field with the side plate and the non side plate is established. The spiral side is found by comparing the vortex discharge and the rise resistance coefficient of the two models. The existence of the plate can obviously reduce the lift coefficient amplitude, but it will increase the mean of the drag coefficient, and the existence of the spiral side will have an effect on the wake vorticity cycle. The flow model has a uniform vortex shedding period from top to bottom and the lift coefficient on each section. The amplitude of the total lift coefficient is reduced greatly, and the amplitude of the overall lift coefficient is reduced. This is not in conflict with the previous research results on the lifting coefficient of the spiral side plate which can reduce the overall lift force. In this paper, the three methods of numerical programming, model experiments and numerical simulations have been carried out on the vortex induced motion of the Spar platform. Some more reliable conclusions are obtained, which are very useful for practical engineering applications. However, the study of vortex induced motion of Spar platform is a new topic both at home and abroad. There are still many aspects in this paper that need to be studied in depth.

【学位授予单位】：中国海洋大学
【学位级别】：博士
【学位授予年份】：2015
【分类号】：TE95

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