【作者】 单丹丹；

【导师】 张洪雨；

【作者基本信息】 哈尔滨工程大学 ， 港口、海岸及近海工程， 2011， 硕士

【摘要】 随着陆地石油储量的越来越少,人们开始将目光放在海底石油的利用和开采上,而海底管道作为一种重要的运输工具,具有输送连续、输送量大、管理方便等优点,目前已在海洋工程中得到了较广泛的应用。通常情况下海底管道所处的海洋环境都非常恶劣,在波浪、潮流等的作用下容易造成管道悬空并失去在位稳定性,所以一般在管道的铺设过程中要对管道进行埋设,传统方法是依靠机械的方式对管道进行埋设,但各类机械设备的价格都很昂贵,为了寻求一种经济有效的方式,人们将一种类似鱼鳍的阻流器装置安放在管道上方,以实现管道的自埋。本文以杭州湾海底管道铺设中的自埋技术为现实依据,应用数值模拟的方法来对比有无阻流器两种情况下海水对管道冲刷产生的不同影响,通过对比说明阻流器对管道自埋的促进作用。首先将海床假想为固壁,模拟有无阻流器管道周围的冲刷情况,通过对管道表面的压力系数、升力系数以及海床剪应力的对比分析,说明阻流器能够导致管道周围水流发生变化,使得管道上方压力变大,升力系数减小,管道下方水流流速变大,冲刷海床,导致海床剪应力增大,这些都对管道的自埋起到了一定的促进作用。而后对管道周围的泥沙海床冲刷进行数值模拟,研究管道下方的冲刷坑形态,同样输出管道表面压力系数分布情况,并且对比管道下方的水流流速情况,从中我们可以看出,添加阻流器的管道表面压力出现了明显的左右不对称情况,这是由于阻流器的阻挡导致管道迎流面顶部压力明显增大,而这也将导致管道的升力系数下降,管道下方的冲刷加剧,从冲刷坑的形态也可以看出,阻流器会使冲刷坑加深,那么管道就会在自重的作用下下沉较快,从而实现自埋。对管道的下沉过程进行模拟,我们可以发现,管道的自埋过程首先是管道下方的泥沙冲刷,形成冲刷坑,由于管道本身存在着重力,这样在重力的作用下会慢慢下沉,被冲刷的泥沙会在管道后方堆积,随着管道的下沉,后方的泥沙将慢慢回填,将管道埋于海床下,这就是管道的实际自埋过程。更多还原

【Abstract】 With less and less oil reserves on land, people began to set their sights on the use and exploitation of undersea oil. Submarine pipelines as an important means of transportation, has many merits, such as continuously deliver, large conveying capacity, and convenience management and so on, so they have been used extensively in ocean engineering currently. Normally because of the severe conditions in marine environment, the pipelines will be suspended and lose its stability caused by wave and tide, so it is generally to embed the pipe during the laying of the pipeline. The traditional method is relaying on mechanical means to realize embedment, but the prices of various types of machinery and equipment are very high, in order to find a cost-effective way, people placed a kind of spoiler device which is similar to the fish fin above the pipe to achieve the self-burial of pipelines. In this paper, basing on the self-buried technology in Hangzhou Bay’s laying of submarine pipelines, apply the method of numerical simulation to compare two kinds of conditions of having spoilers or not on pipelines under the scouring of current. By comparing, it illustrate that the spoiler’s role of promoting in pipelines’ self-burial.Firstly, the sea-bed is assumed to be solid wall, to simulate the scour around the pipeline of having spoilers or not. Through the comparative analysis of pressure coefficient and lift coefficient on the surface of pipe as well as seabed shear stress, it is explain that spoilers are able to cause the changes of flow around the pipeline, so that the pressure above the pipe increase, lift coefficients reduce, flow velocity under the pipe greaten and flush the seabed, finally cause the increasing of seabed shear stress. All of them play an important role in the self-burial of pipelines.Then, simulate that seabed scouring around the pipeline, to study the scour pit pattern below the pipeline and to export the distribution of surface pressure coefficient from the pipeline. Meanwhile, we contrasted the flow velocity below the pipeline. It can be seen that the surface pressure of pipelines adding spoiler device is an obvious left-right asymmetry.Because of the countercheck by spoiler device, it causes the top pressure of pipelines’ meeting flow surface increasing obviously, it will also cause the lift coefficient of pipeline decrease and the scour below the scour intensifies. For the form of scouring pit, spoiler device makes the scouring pit deepen, the pipe will sink rapidly by gravity, so as to realize the self- burial.Simulate the process of pipe sinking, we can see that the process of pipeline self-burial firstly is sediment erosion beneath the pipe, forming the scour hole. Due to the pipe itself exsists gravity, so it will sink slowly under the action of gravity. The sediment washed will be accumulating behind the pipe.With the pipe down, rear sediment will slowly backfill, the pipe then will be buried under the seabed. This is the actual process of pipeline self-burial.更多还原