海流作用下多立柱式Spar平台绕流流场与涡激运动特性研究
发布时间：2018-07-22 20:32
【摘要】：油气资源在未来几十年中仍将占据能源结构的主体地位，而随着我国经济发展，能源需求也日益增大，开发南海深水区域的油气资源能够有效缓解我国能源紧张的压力。Spar平台作为典型的深水浮式平台，由于其具有稳性好，垂荡小，不受水深限制以及良好的经济性等优点，能够成为开发南海油气资源的理想选择。本文所研究的新型多立柱式Spar平台概念应用而生，其硬舱为四根圆柱方形阵列布置加方形中心井的形式，比传统的单立柱式Spar平台更易施工建造。 Spar平台有着诸多优点的同时，也面临着一种特殊的困扰——涡激运动问题。Spar平台的主体为典型的钝体结构，当遭遇一定速度的海流作用时，主体上将会产生流动分离和旋涡脱落，进而引发较大幅度的垂直流向的运动。涡激运动会使得系泊缆和立管上产生较大的张力，对系泊系统和立管系统造成疲劳损伤，使得平台整体的疲劳寿命降低。由于多柱式Spar平台的各柱间会产生复杂的相互干扰，不同于常规的单立柱Spar平台或半潜式平台，因此对其开展相应的绕流和涡激运动研究具有重要意义。 本文通过数值计算方法，对平台整体的绕流特性进行了分析。研究发现：由于平台主体形式的特殊性，在15°和30°来流角下，平台不再关于流向对称，，此时平台所受升力的均值不再为零；除了升力和阻力作用外，平台还受到一定的力矩作用；平台各柱涡结构会在尾流侧汇聚，脱涡形式为单涡街。 在研究平台整体绕流特性的同时，还发现各柱之间存在着复杂的相互干扰。平台的方柱部分尾涡发展受到下游侧圆柱的抑制，且30°来流角时一侧的流动分离规律不同于单方柱绕流。平台四圆柱部分中下游侧圆柱受到的升力波动幅值更大，上游侧圆柱在来流角较低时受到的阻力比单圆柱绕流时大，而在来流角较高时阻力小于单圆柱情况。 采用拖曳水池模型试验手段，研究了是不同来流角、不同流速下平台的涡激运动特性。通过对横荡运动、纵荡运动、水平面内运动轨迹、首摇运动、涡脱频率和水动力系数的分析，可得：在折合速度约为6~8范围内，平台横荡运动存在明显的“锁定”现象（0°来流角无侧板时“锁定”范围约为Ur：7~10）。在0°来流角下较高流速时，减涡侧板对涡激运动有明显的抑制效果。平台的运动轨迹近似与平台硬舱截面的对角线平行（0°来流角除外），这不同于常规的单立柱Spar平台。此外，试验中还观察到较明显的首摇运动。在“锁定”区间范围内，平台的脱涡频率不再随着流速的增大而线性增大，而是近似保持水平。 通过数值模拟方法，从绕流流场角度，对平台的涡激运动现象开展了进一步的研究。相较于平台固定绕流情况，由于平台约束变为了弹性约束，会在涡激力作用下产生涡激运动，平台的尾涡结构会偏向于运动的反方向。在较高来流角下，平台各柱的流动分离特性也会发生改变，分离位置和尾涡结构形式与固定绕流时有较明显的区别。
[Abstract]:Oil and gas resources will still occupy the main position of energy structure in the next few decades, and with the development of China's economy and the increasing demand for energy, the development of the oil and gas resources in the deep water area of the South China Sea can effectively alleviate the pressure of.Spar as a typical deep-water floating platform, because of its good stability, small drooping and unaffected. The limitations of water depth and good economy can be an ideal choice for the development of the South China Sea oil and gas resources. The new multi column Spar platform studied in this paper has been applied and its hard module is arranged with four square cylindrical arrays with square center well, which is more easily constructed than the traditional single column Spar platform.
While the Spar platform has many advantages, it is also faced with a special problem - the main body of the.Spar platform of vortex excited motion is a typical blunt body structure. When the current is encountered at a certain speed, the main body will generate flow separation and vortex shedding and lead to a larger vertical direction movement. Vortex induced motion will make it possible The tension of mooring and riser causes fatigue damage to the mooring system and the riser system, which reduces the fatigue life of the platform as a whole. Due to the complex mutual interference between the columns of the multi column Spar platform, different from the conventional single column Spar platform or the semi submersible platform, the corresponding flow and vortex excitation are carried out. Sports research is of great significance.
In this paper, the flow behavior of the whole platform is analyzed by numerical method. It is found that, due to the particularity of the platform body form, the platform is no longer about the flow symmetry at the 15 and 30 degree angle, and the lifting force is no longer zero. Besides the lift and resistance, the platform is also subjected to a certain moment. The vortex structure of each column will converge on the wake side, and the vortex shedding form is single vortex street.
At the same time, it is found that there is a complex interaction between the columns. The development of the part tail vortex of the square column of the platform is restrained by the downstream side cylinder, and the flow separation law on one side is different from the single square column when the 30 degree angle is coming. The lift fluctuation amplitude of the middle and lower reaches of the four cylinder part of the platform is even more. The resistance of the upstream cylinder is larger than that of a single cylinder when the angle of flow is low, and the resistance of the upstream cylinder is smaller than that of a single cylinder when the flow angle is high.
The characteristics of the vortex excited motion of the platform with different flow angles and different velocities are studied by a towed pool model test. Through the analysis of the sway motion, the longitudinal motion, the moving trajectory in the horizontal plane, the head rolling, the vortex removal frequency and the hydrodynamic coefficient, the motion of the platform is obvious in the range of about 6~8. The "locking" phenomenon is about Ur:7~10 at the time of 0 degrees without side plates. At the high flow rate at the 0 degree angle, the vortex side plate has an obvious suppression effect on the vortex excitation. The trajectory of the platform is parallel to the diagonal of the platform section of the platform (except for the 0 degree angle), which is different from the conventional single column Spar platform. In the "lock" range, the frequency of the platform is no longer linearly increased with the increase of velocity, but the approximate maintenance level.
Through the numerical simulation, the vortex induced motion of the platform is further studied from the angle of flow around the flow field. Compared to the stationary flow situation of the platform, the vortex induced motion will be produced under the action of vortex excitation because the platform constraints become elastic constraints. The tail vortex structure of the platform will be biased toward the reverse direction of the motion. The flow separation characteristics of each column will also change. The separation position and the wake vortex structure are obviously different from the fixed flow.
【学位授予单位】：上海交通大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：U674.38;U661.1
[Abstract]:Oil and gas resources will still occupy the main position of energy structure in the next few decades, and with the development of China's economy and the increasing demand for energy, the development of the oil and gas resources in the deep water area of the South China Sea can effectively alleviate the pressure of.Spar as a typical deep-water floating platform, because of its good stability, small drooping and unaffected. The limitations of water depth and good economy can be an ideal choice for the development of the South China Sea oil and gas resources. The new multi column Spar platform studied in this paper has been applied and its hard module is arranged with four square cylindrical arrays with square center well, which is more easily constructed than the traditional single column Spar platform.
While the Spar platform has many advantages, it is also faced with a special problem - the main body of the.Spar platform of vortex excited motion is a typical blunt body structure. When the current is encountered at a certain speed, the main body will generate flow separation and vortex shedding and lead to a larger vertical direction movement. Vortex induced motion will make it possible The tension of mooring and riser causes fatigue damage to the mooring system and the riser system, which reduces the fatigue life of the platform as a whole. Due to the complex mutual interference between the columns of the multi column Spar platform, different from the conventional single column Spar platform or the semi submersible platform, the corresponding flow and vortex excitation are carried out. Sports research is of great significance.
In this paper, the flow behavior of the whole platform is analyzed by numerical method. It is found that, due to the particularity of the platform body form, the platform is no longer about the flow symmetry at the 15 and 30 degree angle, and the lifting force is no longer zero. Besides the lift and resistance, the platform is also subjected to a certain moment. The vortex structure of each column will converge on the wake side, and the vortex shedding form is single vortex street.
At the same time, it is found that there is a complex interaction between the columns. The development of the part tail vortex of the square column of the platform is restrained by the downstream side cylinder, and the flow separation law on one side is different from the single square column when the 30 degree angle is coming. The lift fluctuation amplitude of the middle and lower reaches of the four cylinder part of the platform is even more. The resistance of the upstream cylinder is larger than that of a single cylinder when the angle of flow is low, and the resistance of the upstream cylinder is smaller than that of a single cylinder when the flow angle is high.
The characteristics of the vortex excited motion of the platform with different flow angles and different velocities are studied by a towed pool model test. Through the analysis of the sway motion, the longitudinal motion, the moving trajectory in the horizontal plane, the head rolling, the vortex removal frequency and the hydrodynamic coefficient, the motion of the platform is obvious in the range of about 6~8. The "locking" phenomenon is about Ur:7~10 at the time of 0 degrees without side plates. At the high flow rate at the 0 degree angle, the vortex side plate has an obvious suppression effect on the vortex excitation. The trajectory of the platform is parallel to the diagonal of the platform section of the platform (except for the 0 degree angle), which is different from the conventional single column Spar platform. In the "lock" range, the frequency of the platform is no longer linearly increased with the increase of velocity, but the approximate maintenance level.
Through the numerical simulation, the vortex induced motion of the platform is further studied from the angle of flow around the flow field. Compared to the stationary flow situation of the platform, the vortex induced motion will be produced under the action of vortex excitation because the platform constraints become elastic constraints. The tail vortex structure of the platform will be biased toward the reverse direction of the motion. The flow separation characteristics of each column will also change. The separation position and the wake vortex structure are obviously different from the fixed flow.
【学位授予单位】：上海交通大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：U674.38;U661.1
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