冲蚀固床上海底子母管结构水动力特性的数值研究

发布时间：2018-06-19 14:12

本文选题：子母管线 + 冲姓坑　；参考：《大连理工大学》2014年硕士论文

【摘要】：本文采用数值模拟的方法研究了冲蚀固床上的子母管线在规则波作用下的水动力特性,为工程设计人员进行海底子母管线的设计和安全性评估工作提供了有价值的科研理论成果和指导。本文采用三步有限元法离散雷诺方程,并通过标准k-co模型来模拟水波的湍流运动,采用CLEAR-VOF法捕捉水体的自由表面,利用可吸收式无反射造波技术建立了数值波浪水槽。文中通过数值计算结果和物理模型试验数据的对比,从波面历时曲线、管线水动力荷载历时曲线、管线周围涡脱模式三个方面验证了数值计算结果的可靠性。本文的数值模型可以用来进行子母管结构的水动力特性的研究。本文基于所建立的数值水槽,数值研究了底床上冲蚀坑的存在对子母管线的水动力荷载的影响,并考察了涡的运动和管线所承受的荷载的振荡变化特征之间的关系,分析了冲蚀坑相对深度S/D、KC数对子管和母管的拖曳力系数、惯性力系数、升力系数以及升力振荡频率的影响。研究结果表明,冲蚀坑的存在使得子管和母管的水平力和升力幅值比平底地形时的有所减小,子管升力和母管升力的振荡出现倍频现象,且存在一定的相位差。在规则波浪作用下,子母管周围的涡量场重复进行着涡的脱落和反向粘附现象,而涡的脱落和反向粘附使得子管升力和母管升力达到极值。随着冲蚀坑相对深度的增大,母管的拖曳力系数呈现先增大后减小的趋势,母管的惯性力系数和正向升力系数逐渐减小并趋向于平稳,负向升力系数则不断增大,而冲蚀坑深度的变化对子管水动力系数的影响很小。通过对冲蚀固床上单管结构和子母管结构的水动力荷载进行对比,得出子管的存在使得母管的水平力幅值减小约50%,而母管的升力幅值则有所增大,且升力的方向更多的表现为负向。随着KC数的增大,子管和母管的拖曳力系数和升力系数逐渐减小并趋向于稳定,而惯性力系数则逐渐增大；同时,KC数的增大使得子母管周围的湍流特征越来越明显,子管和母管的升力频谱曲线出现多个峰值,但是升力频谱曲线的主峰对应的频率恒为2倍波浪振荡频率。
[Abstract]:In this paper, numerical simulation method is used to study the hydrodynamic characteristics of the parent pipeline on the erosion solid bed under the action of regular waves, which provides valuable scientific research results and guidance for the engineering designers to design and evaluate the safety of the subseabed pipeline.
In this paper, the three step finite element method is used to discrete the Reynolds equation, and the turbulence motion of water wave is simulated by the standard K-co model. The free surface of the water body is captured by CLEAR-VOF method. The numerical wave tank is established by the absorbable non reflective wave making technology. The time curve, the diachronic curve of the hydrodynamic load of the pipeline and the three aspects of the vortex removal mode around the pipeline verify the reliability of the numerical calculation results. The numerical model of this paper can be used to study the hydrodynamic characteristics of the tube structure.
Based on the numerical water trough established in this paper, the influence of the existence of the erosion pit on the bottom bed on the hydrodynamic load of the parent pipeline is numerically investigated, and the relationship between the vortex motion and the vibration characteristics of the load under the pipeline is investigated. The drag force coefficient and the inertial force system of the relative depth of the erosion pit S/D, the number of KC to the tube and the mother tube are analyzed. The results show that the existence of the erosion pits makes the horizontal force and lift amplitude of the tube and the mother tube decrease slightly than that in the flat bottom, and the oscillation of the lift force and the lift of the mother tube appears frequency doubling, and there is a certain phase difference. Under the action of regular waves, the vortex around the tube. The volume field repeats the phenomenon of vortex shedding and reverse adhesion, and the vortex shedding and reverse adhesion make the lift force and the lift force of the mother tube reach the extreme value. As the relative depth of the erosion pit increases, the drag coefficient of the mother tube increases first and then decreases, and the number of inertial force and the positive lift coefficient of the mother tube gradually decrease and tend to Yu Ping. The influence of the change of the negative lift coefficient on the hydrodynamic coefficient of the tube is very small. By comparing the single tube structure and the hydraulic load of the tube structure on the erosion solid bed, it is concluded that the existence of the sub tube reduces the horizontal force amplitude of the mother tube by about 50%, while the lift amplitude of the mother tube is increased. The direction of lifting force is more negative. With the increase of KC number, the drag force coefficient and lift coefficient of the tube and the mother tube gradually decrease and tend to be stable, while the inertia force coefficient increases gradually. At the same time, the increase of the KC number makes the turbulence characteristics around the tube more and more obvious, and the lift spectrum curve of the sub tube and the mother tube appears more than one. Peak value, but the frequency corresponding to the main peak of the lift spectrum curve is 2 times the wave oscillation frequency.
【学位授予单位】：大连理工大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：P756.2

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