自升式平台圆柱桩腿局部冲刷的数值模拟研究

发布时间：2018-01-14 01:14

本文关键词：自升式平台圆柱桩腿局部冲刷的数值模拟研究　出处：《西南石油大学》2015年硕士论文　论文类型：学位论文

【摘要】：随着我国快速发展对油气能源的需求逐渐增大,陆上油气资源随着长期开采日渐匮乏,油气资源开采逐渐向海洋倾斜,目前对海洋油气资源开采主要集中在近海,而自升式海洋平台是近海油气开采的重要工具。处于海洋水流环境中的自升式海洋平台圆柱型桩腿周围通常都会产生局部冲刷,当冲刷严重时更会影响平台桩基的稳定性,导致平台事故的发生。目前国内外学者对于此类问题的研究主要集中在桥梁圆柱桥墩的局部冲刷和比例模型实验,而针对实际尺寸的海洋平台圆柱桩腿在不同水流条件下的局部冲刷的研究较少。为此,本文构建了单向水流条件下的局部冲刷模型、波浪模型、波流模型及其冲刷模型等一系列数值模型,采用国内外具有一定较高水平和知名度的模型实验结果进行对比验证数值模型的合理性和准确性,并模拟分析不同影响因子对实际尺寸平台桩腿局部冲刷的影响规律、局部冲刷的形成过程、局部冲刷的作用机理和冲刷坑的形态,获得的研究成果能对海洋平台圆柱桩腿局部冲刷的防护措施、结构优化和安全评估提供重要参考。本文完成的研究工作主要分为以下几个部分： (1)文献调研与分析。对单向水流条件下局部冲刷的作用机理和前人的研究成果进行调研和综述,并对目前研究较多的桥梁局部冲刷进行概述,讨论了前人对不同条件下的圆柱局部冲刷的研究成果；对运动中的泥沙分类、受力和波流联合条件下的泥沙运动特征进行了概述。 (2)概述模拟中使用的数学模型和数值计算方法。对研究中用到的模拟软件、控制方程和泥沙运输模型等数学模型进行概述,使用Roulund的实验结果与模拟结果进行对比,对两种湍流模型进行优选。 (3)单向水流条件下局部冲刷模型的构建及验证。构建了单向水流条件下的圆柱局部冲刷模型,将圆柱周围流场特征及局部冲刷的模拟结果与Melville的实验结果进行对比,验证泥沙运输模型的可靠性。 (4)波浪模型的构建以及孔隙结构消波研究。构建了一系列三维波浪模型,对模型中孔隙结构的消波效果进行研究,对孔隙结构消波效果影响较大的孔隙率、材料粒径和结构斜坡坡度进行分析研究,获得最优的孔隙结构消波参数组合。 (5)波流联合模型及其局部冲刷模型的构建及验证。先后构建了波流联合作用模型及其冲刷模型,针对波流联合模型的流体体积不守恒问题,设置出口边界为压力出流边界；选用Van Rijn的实验结果对比验证模型垂直水流流速的合理性；对波流联合条件下的圆柱局部冲刷进行模拟,并与Qi的实验结果进行对比验证,验证数值模型在波流条件下局部冲刷模拟结果的可靠性。 (6)研究不同条件下海洋平台圆柱桩腿局部冲刷的变化规律。调研胜利作业三号平台的事故,分析事故原因,指出平台桩腿局部冲刷与事故发生的联系；对桩腿局部冲刷影响较大因子如：流速、水深、桩腿直径和波流作用下不同波高进行模拟分析,研究影响因子变化对桩腿局部冲刷的影响及其作用机理。总之,本文结合自升式平台圆柱桩腿局部冲刷的研究现状,运用计算流体力学、泥沙运动力学、波浪理论等学科知识构建了一系列数值模型进行模拟研究,实现了桩腿的局部冲刷的模拟,并获得了不同环境条件下的局部冲刷变化规律。研究成果能够为自升式海洋平台的安全评估、防护措施和结构优化提供重要参考,具有较高的理论意义和工程实用价值。
[Abstract]:With the rapid development of our country , the demand of oil and gas energy gradually increases , and the oil and gas resources are gradually inclined to the sea as the long - term exploitation becomes scarce . At present , the exploitation of offshore oil and gas resources is mainly concentrated in the offshore , and the self - elevating offshore platform is an important tool for offshore oil and gas exploitation . In this paper , a series of numerical models , such as local scour model , wave model , wave - flow model and scour model , are studied in this paper . The work done in this paper is mainly divided into the following parts : ( 1 ) Literature investigation and analysis . The mechanism of local scour under the condition of one - way water flow and the research results of the former are summarized , and the results of local scour of the cylinder under different conditions are discussed . ( 2 ) The mathematical model and numerical calculation method used in the simulation are summarized . The mathematical models of simulation software , control equation and sediment transport model used in the study are summarized , and the experimental results of Roulund are compared with the simulation results , and the two turbulence models are preferred . ( 3 ) constructing and verifying the local scour model under the condition of one - way water flow , and constructing a cylindrical local scour model under the condition of one - way water flow , comparing the characteristics of the flow field around the cylinder and the simulated results of local scour with the experimental results of Melville , and verifying the reliability of the sediment transport model . ( 4 ) Construction of wave model and wave elimination research of pore structure . A series of three - dimensional wave model is constructed to study the wave - eliminating effect of pore structure in the model . ( 5 ) The combination model of wave current and its local scour model are constructed and verified . The joint action model of wave current and its scouring model are constructed . For the problem of non - conservation of fluid volume in the joint model of the wave flow , the outlet boundary is set as the pressure outlet boundary ; the experimental results of Van Rijn are used to compare the rationality of the vertical water flow velocity of the model , and compared with the experimental results of Qi , the reliability of the numerical model is verified under the condition of wave flow . ( 6 ) To study the regularity of local scour of the cylindrical pile legs of offshore platform under different conditions , and investigate the cause of accident , point out the connection between the local scour and accident of the platform pile legs , and analyze the influence factors on the local scour of the pile legs . In conclusion , this paper constructs a series of numerical models by means of computational fluid mechanics , mud - sand movement mechanics and wave theory to simulate the local scour of the self - elevating platform cylindrical pile leg , and realizes the local scour rule under different environmental conditions . The research results can provide important reference for the safety assessment , protection measures and structural optimization of the self - elevating offshore platform , and has higher theoretical significance and practical value .

【学位授予单位】：西南石油大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TE951

【参考文献】