深水浮式平台截断物理模型试验的阻尼等效补偿研究

Physical model tests of deep water floating platform play a key role in solving practical engineering problem and scientific research. At present, hybrid model tests which combined a passive truncation with subsequent numerical simulation is the only practical application because of the limited dimension of wave basin, but the maximum predicting error may reach 30% due to the difference of dynamic characteristic between the truncated and full-depth mooring line. In terms of this situation, the effect mechanism of mooring induced damping and its calculation method are investigated firstly. Secondly, the optimization design model of truncated mooring system based on static equivalent and mooring damping equivalent in low frequency range is investigated. And then, a new model test method combining passive truncation with mooring damping compensated system is proposed. The damping compensation method in truncated mooring system is investigated and its compensation device is developed. Model test technology of passive truncation combining with mooring damping compensated system is established, and predicting results of motion responses can be directly obtained via physical test. Furthermore, characteristics of response between platform and mooring system are investigated, and its nonlinear full coupling calculation models are established in time domain. Finally, the model tests of a semi-submersible platform and a Spar platform respectively using passive truncated mooring system and viscous damper compensated system are investigated. .Through this research project, a set of physical model test method and technology is established in predicting motion responses of deep water floating platform truly and reliably, which will also provide reliable basis for urgent need to design and construct deep water floating platform in oil and gas field development of South China Sea.

深水浮式平台物理模型试验在解决实际工程问题和科学研究中起关键作用。受水池条件限制，目前唯一实际应用的"被动截断+数值模拟"混和模型试验方法由于其截断锚泊线和全水深锚泊线动力特性差异，其最大误差可达30%。针对此现状本项目首先研究锚泊系统阻尼的作用机理，建立其计算方法；其次建立基于静力和低频阻尼等效的截断锚泊系统优化设计模型；然后提出"被动截断+锚泊阻尼补偿"模型试验方法：研究截断锚泊系统阻尼补偿方法并研发其补偿装置，建立"被动截断+锚泊阻尼补偿"模型试验技术，实现由物理试验可直接给出运动响应预报结果；进而研究平台及锚泊系统的响应特征，在时域内建立其非线性全耦合计算模型；最后结合半潜式平台和Spar平台，分别进行被动截断和粘滞阻尼器补偿模型试验研究。.通过本项目研究，建立一套真实可靠预报深水浮式平台运动响应的物理模型试验方法和技术，为我国南海油气田开发亟需的深水浮式平台设计建造提供可靠依据。

物理模型试验对于解决深水浮式平台设计的工程问题，以及研究浮式平台及其锚泊系统之间的非线性耦合效应等科学问题均能够起到关键的作用。受到目前可用的海洋工程水池条件限制，目前唯一实际应用的“被动截断+数值模拟”混和模型试验方法由于其截断锚泊线和全水深锚泊线动力特性差异，使得浮式平台运动响应的预报结果最大误差可达30%。针对此现状，本项目首先分别应用拟静力和非线性动力有限元方法，计算锚泊系统阻尼，分析锚泊阻尼的作用机理及特性，结合水池试验，建立了有效计算锚泊系统阻尼的数值方法；其次运用遗传优化算法，建立了基于静力和低频阻尼等效的截断锚泊系统优化设计模型，并设计得到多组截断锚泊系统；接着建立了锚泊线的非线性有限元动力分析模型，研究截断水深锚泊线和全水深锚泊线在遭受相同环境荷载激励时的运动响应，分析两种锚泊线的张力和锚泊阻尼变化规律，比较了两者动力特性的差别；然后提出了“被动截断+锚泊阻尼补偿”模型试验方法：研究截断锚泊系统阻尼补偿方法并研发其补偿装置，建立“被动截断+锚泊阻尼补偿”模型试验技术，实现了由物理试验可直接给出浮式平台的运动响应预报结果；进而研究了浮式平台及锚泊系统的响应特征，在时域范围内建立了非线性的全耦合数值计算模型；最后结合一座典型的半潜式平台，分别进行被动截断和粘滞阻尼补偿模型试验研究，将试验结果和数值计算结果进行比较，验证了本项目提出的深水浮式平台截断试验及其等效补偿方法的可行性。.通过本项目研究，对深水浮式平台的被动截断物理模型试验方法进行了发展和改进，使得截断锚泊线和全水深锚泊线两者之间的静动力特性均趋于一致，从而使浮式平台的运动响应预报结果更加真实和可靠，为我国南海油气田开发亟需的深水浮式平台设计建造提供了可靠的依据。