【作者】 王建伟；

【导师】 孙丽萍；

【作者基本信息】 哈尔滨工程大学 ， 船舶与海洋结构物设计制造， 2020， 博士

【摘要】 张力腿平台(Tension Leg Platform,TLP)作为一种新型的海洋浮式系统,其运动性能决定了这种类型的平台在深水领域的应用和油气开发中越来越受到国际社会的重视,同时,国内也掀起了相关技术研究的高潮。这对于我国打破国外海工深水技术垄断,促进我国海洋科技的进步具有重要的战略意义。而TLP在复杂海洋环境的运动问题研究一直是海洋工程领域的热点和难点。半刚性半顺应式的结构形式使得TLP能够有效避开由海洋常见频率所引起的平台共振现象,但是在双色波作用下平台本体可能会发生高频共振及慢漂等现象,进而影响平台的运动特性和筋腱的疲劳寿命。鉴于海洋环境的随机性和复杂性,TLP的动力响应和系泊特性又带有较大的简化,基于此种情况,本文所研究的TLP数学模型充分考虑了平台本体运动的耦合、筋腱振动的耦合以及平台本体与筋腱之间的耦合。论文主要研究在波浪和海流联合作用下TLP的三维时域耦合运动响应问题。将TLP在波浪中的运动响应研究主要分成三部分:平台本体在波浪中的三维时域响应研究、张力腿筋腱的振动响应研究以及平台本体与张力腿筋腱的时域耦合运动响应研究。求解平台本体在波浪中时域运动响应问题的关键在于三维自由面时域Green函数的数值计算。基于Bessel函数的性质,本文利用时域Green函数及空间导数所满足的常微分方程,首次提出采用最小二乘支持向量机(LS-SVM)理论对该微分方程进行求解。LS-SVM算法能够有效的提高时域Green函数及空间导数的求解精度和稳定性。基于上述时域Green函数的计算方法,编译平台本体在波浪中的时域运动响应程序,并进一步讨论分析波浪粘性对平台本体受力和运动的影响。当研究平台处于静态偏移情况下TLP的运动响应时,将张力腿筋腱简化成无质量的线性弹簧结构,建立计及筋腱影响下的恢复力矩阵,该矩阵还考虑了平台水平偏移(offset)和垂直下沉(setdown)耦合效应的影响。当筋腱处于不同倾斜角时,研究水平偏移对TLP波频运动的影响,并进一步分析平台水平偏移和垂直下沉的耦合效应对TLP运动响应的影响。在平台、波浪和海流的联合作用下,基于Kirchhoff假设并运用Hamilton原理,建立计及筋腱轴向振动与流向振动耦合效应的张力腿筋腱振动模型。其中筋腱顶端的边界条件除了计及平台波频运动的影响外,还考虑了平台发生的静态偏移和垂直下沉现象的影响。应用伽辽金(Galerkin)法对张力腿筋腱的振动方程进行数值计算,通过研究不同参数激励作用下筋腱的轴向振动和流向振动,归纳总结张力腿筋腱轴向振动和流向振动的振动规律与原因,给出影响筋腱疲劳寿命的主要影响因素。在研究平台本体与张力腿筋腱的耦合运动响应时,利用平台本体与张力腿筋腱的相互作用力,建立耦合TLP模型。该计算模型同时考虑平台运动的耦合效应与张力腿筋腱轴向振动与流向振动的耦合效应。基于该模型的计算程序研究TLP的波频运动、水平偏移和垂直下沉等现象的耦合效应对TLP运动响应的影响。在研究二阶波浪力对平台本体与张力腿筋腱运动响应的影响时,TLP的运动方程同时计及不规则波的平均漂移力、二阶差频力与二阶和频力的影响。基于平台运动固有周期分别研究二阶波浪力对平台本体和张力腿筋腱的运动、水平偏移和垂直下沉的影响。综上所述,论文研究从浪向、水深、预张力、海流流速、静态偏移和二阶力等影响TLP动力响应的不同因素着手,外部载荷从规则波、随机海浪的双色波到浪流的联合作用,逐步深入,层层递进,汇集平台本体的水动力模型、筋腱的振动模型、TLP的非耦合模型和耦合模型,讨论研究平台运动的耦合效应、筋腱振动的耦合效应以及水平偏移与垂直下沉的耦合效应等这些因素对TLP水动力特性的影响,全面开展TLP在海洋环境中的动力响应研究,为系统掌握TLP的运动性能提供理论依据。更多还原

【Abstract】 As a new type of Marine floating system,tension-leg platform has attracted more and more attention from the international community due to its motion performance.At the same time,the domestic also set off the research climax of the deep-water engineering technology.It is of great strategic significance for China to break the monopoly of offshore deep-water technology and promote the progress of Marine science and technology.The research on the motions of TLP in complex Marine environment has been one of the important topics in the field of Marine engineering.Although the semi-rigid and semi-compliant structure enables TLP to effectively avoid the platform resonance phenomenon caused by common frequencies in the ocean,sum frequency and difference frequency forces may cause the platform occur in the plane of springing,ringing and slow drift phenomenons,which affect the movement characteristics of the platform and the fatigue life of tether.Given the randomness and complexity of Marine environment,the dynamic responses and mooring characteristics of TLP in waves are greatly simplified.Based on this situation,TLP mathematical model in this paper is fully considered the coupling of platform motions,the coupling of tether vibrations and the coupling between platform and tethers.The main research object of this paper is TLP.And the 3-D time-domain coupled motion responses of TLP under the action of wave and current are studied.In order to analyze the motions of TLP in detail,this paper will be divided into three parts:the time domain response of platform in waves,the vibration responses of tethers and the uncoupled and coupled motion responses of platform and tethers.The key to solving the time-domain response of platform in waves is to realize the precise and stable numerical calculation of 3-D time-domain Green functions.Based on the properties of Bessel function and ordinary differential equation satisfied by time-domain Green function and its space derivatives,the least squares support vector machine(LS-SVM)theory is firstly proposed to solve this differential equation.LS-SVM algorithm can effectively improve the accuracy and stability of solving time-domain Green function and its space derivatives.Based on the above calculation method of time-domain Green function,the motion response programs of platform in waves are compiled.Furthermore,the influence of wave viscosity on the force and motion of the platform is discussed.In the study of TLP movements when tethers are inclined,the tethers are simplified into a massless linear spring structure,and the restorative force matrix is established taking into account the influence of tethers.At the same time,the coupled effects of horizontal offset and vertical setdown of the platform are considered.By studying the motions of TLP when tethers are in different inclination angles,the influence of horizontal offset on the platform is obtained,and the influence of the coupled effect of horizontal offset and vertical setdown on the TLP motions is further studied.Under the action of platform,wave and ocean current,a tether vibration model is established based on Kirchhoff s hypothesis and Hamilton principle,which takes into account the coupled effect of axial and transverse vibrations of tethers.Besides the influence of wave frequency movements,the static offset and setdown of the platform are also considered.The nonlinear vibration equations of tethers are analyzed by Galerkin method.The axial and transverse vibrations of tethers under the excitation of different parameters are calculated.The vibration rules and causes of axial and transverse vibrations of tether are summarized,and the main factors affecting the fatigue life of tether are given.When the coupled motion responses between the platform and tethers are studied,the interaction forces between the platform and tethers are used to establish the coupled TLP model by combining the motion equations of platform and the vibration equations of tethers.The coupled effect of platform motions and vibrations of tether are considered in the model.The coupled effects are discussed from the motion responses,horizontal offset and vertical setdown of TLP.In order to study the influence of second-order wave forces on the motion responses of TLP,the motion equations of TLP simultaneously takes into account the influence of the mean drift force,second-order difference frequencies force and second-order sum frequencies force of irregular waves.Based on the natural periods of the platform,the influence of second-order wave forces on the movements of platform and tethers are discussed.In conclusion,starting from different factors affecting the dynamic responses of TLP,such as wave direction,water depth,pretension,sea current velocity,static offset and second order force,the hydrodynamic performances of TLP are calculated.External load is considered from regular wave,random wave to combined wave-current.This study is carried out step by step and takes the integration of the hydrodynamic model of the platform,the vibration model of the tether,the uncoupled model and the coupled model of TLP.At the same time,the coupled effects of platform movements,the coupled effects of tether vibrations and the coupled effects of offset and setdown on the coupled TLP model are analyzed The dynamic responses of TLP in Marine environment are studied comprehensively,so as to provide theoretical basis to master the motion performance of TLP systematically.更多还原