In a complex marine dynamics environment, the consideration of fluid-structure-seabed interaction (FSSI) plays a vital role in reliably analyzing the dynamic response of marine structures, and in assessing their structural dynamic stability. Currently, the predominant numerical analysis used worldwide for the problems of wave-seabed interaction and seawater-structure-seabed interaction is primarily the one-way coupling method. While only a few two-way coupled models are being developed. Consequently, two issues are brought up: (1) For the cases involving small deformation and displacement, the degree of discrepancy can't be quantitatively identified between the results obtained respectively from one-way coupling models and two-way coupled models which are more rigorous in mathematics and physics. (2) For the cases involving large deformation and displacement, one-way coupling models should be non-applicable. To address this problem, this study first proposes an explicit two-way coupling theory for the fluid-structure-seabed interaction. Then, a two-way coupled numerical model is developed by integrating the soil-structure dynamics software FssiCAS, and an OpenFOAM-based CFD solver OlaFlow by utilizing the data exchange library preCICE. This two-way coupled model has been embedded into the software FssiCAS. The reliability of the developed two-way coupled model is systematically validated through a rigorous verification process. Subsequently, a comparative study is conducted between the newly developed two-way coupled model and the existing one-way coupling model, to investigate the ocean wave-seabed interaction, as well as the interaction process between ocean wave, a breakwater, and seabed foundation. A comprehensive analysis is performed by comparing the differences in the wave profiles in fluid domain, dynamic displacement of structure and seabed foundation, seepage, pore pressure accumulation, and liquefaction in seabed foundation solved by the two-way and one-way coupled models. Finally, the suitability of the one-way and two-way coupled models in different applicable scenarios was discussed.

中文翻译：

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流-固-海床相互作用 （FSSI） 双向耦合数值模型的广义框架：显式算法


在复杂的海洋动力学环境中，考虑流-固-海床相互作用 （FSSI） 对于可靠地分析海洋结构的动力学响应和评估其结构动态稳定性起着至关重要的作用。目前，世界范围内用于波-海床相互作用和海水-结构-海床相互作用问题的主要数值分析主要是单向耦合方法。虽然只有少数双向耦合模型正在开发中。因此，提出了两个问题：（1） 对于涉及小变形和位移的情况，分别从数学和物理学中更严格的单向耦合模型和双向耦合模型获得的结果之间无法定量识别差异程度。（2） 对于涉及大变形和位移的情况，应不适用单向耦合模型。为了解决这个问题，本研究首先提出了一种明确的流体-结构-海床相互作用的双向耦合理论。然后，利用数据交换库 preCICE，集成土-结构动力学软件 FssiCAS 和基于 OpenFOAM 的 CFD 求解器 OlaFlow，开发双向耦合数值模型。这种双向耦合模型已嵌入到 FssiCAS 软件中。通过严格的验证过程，系统地验证了所开发的双向耦合模型的可靠性。随后，对新开发的双向耦合模型与现有的单向耦合模型进行了比较研究，以研究海浪与海床的相互作用，以及海浪、防波堤和海底基础之间的相互作用过程。 通过比较双向和单向耦合模型求解的流体域波浪剖面、结构和海底基础的动态位移、渗流、孔隙压力积累和海底基础液化的差异，进行了综合分析。最后，讨论了单向和双向耦合模型在不同适用场景下的适用性。