【作者】 宋志军；

【导师】 滕斌；

【作者基本信息】 大连理工大学 ， 港口、海岸及近海工程， 2010， 硕士

【摘要】 在世界上许多海域中尤其是在陆架、海峡等地形变化剧烈的海区观测到了内孤立波的存在。其中,我国南海北部、台湾东北海域及巴士海峡是内孤立波的多发区,而且常常具有较大的振幅。与表面波相比,内孤立波的恢复力较小,但内孤立波有较大的振幅和较低的频率。本文计算了内孤立波对海上结构物的作用及海上结构物的运动响应,并将此结果与表面波作用下的数值结果进行了比较。首先,在Kdv方程的基础上,模拟了内孤立波的波面,并计算和分析了内孤立波流场中水质点速度和任意点动压强的变化规律。建立了内孤立波对运动结构物作用的时域模型。为了增加本模型的适应性,海上结构物被分解为杆单元和面单元。杆单元上的内孤立波力应用Morison公式求解,面单元上的内孤立波力通过动压强在面单元上积分求得。本文在Kdv型内孤立波理论的基础上求解了运动Spar平台上的内孤立波力和浮力；在悬链线理论的基础上应用迭代方法计算了分段式锚泊系统的锚链力,得到了锚链力与位移之间的非线性关系；利用4阶Runge-Kutta方法求解了结构物的运动方程,得到了结构物在内孤立波作用下的运动响应。应用以上数值模型详细分析了内孤立波对Spar平台的作用、Spar平台的运动响应和锚泊系统锚链力的变化。应用频域边界元方法计算了表面波对Spar平台的作用及其运动响应。对比了内孤立波和表面波对Spar平台的作用,证实了内孤立波对海上结构物的作用是不可忽略的。在内孤立波作用下,Spar平台产生了很大的水平位移。内孤立波对Spar平台的低频作用是Spar平台产生很大水平位移的主要因素。当Spar平台上最大水平内波力是最大水平表面波力的5%左右时,Spar平台在内孤立波作用下最大水平位移是表面波作用下最大位移的3倍左右。可见,内孤立波对海上结构物的影响不仅体现在较大的内波作用力上,更体现在内孤立波对海上结构物的低频运动响应上。更多还原

【Abstract】 Internal solitary waves can be observed in many sea areas around the world, especially in domains with rapidly changing topography, such as near continental shelves and straits. It is estimated that there are more internal solitons whose amplitude is often larger in the northern South China Sea, the sea of northeastern Taiwan and Bashi Channel than other sea areas. Compared with surface wave, the resilience of internal soliton is smaller, while the amplitude is larger and the frequent is lower. In this paper, the action of internal solitons on offshore structures and motion respondences of these structures are both computed; and the numerical results are compared with effects of surface wave, respectively.First of all, the internal solitary wave surface is simulated through the Kdv equation, and the velocity of water particle and the pressure of any point in the flow field of internal soliton is calculated and analyzed.Then, a numerical model to compute the effect on moving structure of internal solitary wave is established. In order to increase the adaptability of this model, marine structures are decomposed into pole elements and face elements. The forces of internal soliton on the pole elements are computed by Morison equation, on the face elements by the integral of dynamic pressure. The solitary wave force and buoyancy are solved through Kdv internal soliton theory. Based on the catenary theory, this paper calculates the force of the sectional anchor mooring system and the nonlinear relationship between anchor force and displacement. The motion respondences of the Spar platform under influence of internal solitary wave are also simulated by making use of the fourth order Runge-kutta method. With these results, the paper detailedly presents the actions of internal solitary wave on the Spar platform, its responses and changes of the anchor force.The boundary element method in frequency domain is applied to compute the action of internal solitary wave on the Spar platform and its response. It is proved that the action of internal soliton on offshore structure can not be ignored by comparing the action of internal solitary wave and surface wave on the Spar platform. Under the force of the internal soliton, the Spar platform produces a great horizontal displacement. Therefore, the low-frequency effect of internal solitary wave plays a significant role in the horizontal displacement of the Spar platform. It is simulated that when the maximum horizontal force on the Spar platform of the internal soliton is about 5%of that of the surface wave, the maximum horizontal displacement of Spar platform under internal solitary wave is about 3 times of that under surface wave. It can be concluded that the influence of internal soliton on marine structure is represented by great forces as well as the low-frequency effect.更多还原