内外流作用下深海立管流固耦合效应与力学模型研究

In the ocean engineering, flexible risers are frequently employed for conveying liquids of oil and natural gas with high temperature and pressure. Consequently, complex internal flows are generated inside of the risers with external fluid load of complicated ocean currents also acting on outside surface of the risers. The combined actions of internal and external flows trigger dynamic responses of high amplitude, which ultimately may causes fatigue damage to the associated risers. However, the multi-fields coupling mechanism for the interactions of internal flow, flexible structure and external flow is still unclear. Motivated by this, the present research will study to establish fidelity numerical model of Fluid-Structure-Interaction (FSI) for the long flexible riser conveying liquids on the basis of the theories of FSI mechanics, computational mechanics, vibration analysis and signal analysis as well. High order discretization schemes for direct numerical simulations (or implicit large eddy simulations) of the newly developed FSI model will also be established. Furthermore, high performance computing with MPI parallelisation and model experiment will be conducted to analyze the vortex-induced vibration and the nonlinear responses of the deep ocean riser conveying liquids to reveal the effects of Reynolds number of internal flow and shear ratios of external flow, as well as the influence of geometrical and material properties on the resonance responses, and finally to clarify the combined mechanisms of internal flow, external shear flow and their coupling with flexible risers. The present research not only has academic significance for developing fundamental theories of FSI mechanics, but also provides a theoretical basis for development and design of novel deep sea oil and gas platforms in South China Sea.

深海油气工程中的细长立管因输送高温、高压原油或天然气而在管内形成复杂内流运动，同时管外经受多变海洋环境引起的外流载荷作用。在内、外流共同作用下，深海立管结构易发生大幅振动响应甚至疲劳损毁。然而，这类内流-结构-外流的耦合效应及力学机理尚不清楚。本项目运用流固耦合力学、计算力学、振动分析和信号分析等理论方法和研究手段，建立内、外流共同作用下的细长柔性管道结构多场流固耦合力学模型，构建直接数值模拟（或隐式大涡模拟）高精度离散格式和数值计算技术。结合高性能并行计算和模型实验，分析深海输流管道涡激振动及其几何非线性动力响应特性，揭示内流雷诺数、外流剪切率，以及结构几何属性与材料性能参数对共振响应特征的影响机理和规律，阐明内流效应、剪切效应和流固多元耦合效应。本研究成果对发展流固耦合力学基础理论有显著学术意义，亦为我国深海油气工程中输油立管设计和安全运行提供力学依据和技术支撑。

深海油气工程中的细长立管因输送高温、高压原油或天然气而在管内形成复杂内流运动， 同时管外经受多变海洋环境引起的外流载荷作用。在内、外流共同作用下，深海立管结构易发生大幅振动响应甚至疲劳损毁。然而，这类内流-结构-外流的耦合效应及力学机理尚不清楚。 本项目运用流固耦合力学、计算力学、振动分析和信号分析等理论方法和研究手段，建立了内、 外流作用下的细长柔性管道结构流固耦合力学模型，构建了直接数值模拟(或隐式大涡模拟)高精度离散格式和数值计算技术。结合高性能并行计算和模型实验，分析了细长管道涡激振动及其非线性动力响应特性，揭示了内流雷诺数、外流剪切率，以及结构几何属性与材料性能参数对振动响应特征的影响机理和规律，阐明内流效应、剪切效应和流固多元耦合效应。本研究成果对发展流固耦合力学基础理论有显著学术意义，亦为我国深海油气工程中输油立管设计和安全运行提供力学依据和技术支撑。