# Numerical Simulation of a Submerged Floating Tunnel: Validation and Analysis
## 1 Introduction
[12] found that the dynamic response of SFTs to seismic traveling waves is significant, with the most unfavorable response site being the connection between an SFT and its bank foundation. [PERSON] and [PERSON] [13; 14] proposed an anchor-displacement calculation method that integrates along the height of the SFT by parts, which demonstrated the advantages of simplicity and feasibility. [PERSON] and [PERSON] [15; 16; 17] have conducted the first experimental studies of a scaled-down model of an SFT under seismic conditions using an underwater shaking table, which revealed that horizontal seismic excitation could cause the horizontal rotation of an SFT tube. Additionally, the seismic response under an anchor cable inclination angle of 45\({}^{\circ}\) was less than that under an anchor cable inclination angle of 60\({}^{\circ}\). As described above, there have been detailed studies of SFTs under seismic conditions, based on the models and numerical calculations of coupling between SFTs' tubes and support systems, and the fluids in which they are submerged. These studies have focused on various aspects of SFTs, such as their dynamic responses, how they are affected by fluid forces, and the dynamic characteristics of anchor cables. The calculation methods and research results generated from these studies have significantly contributed to the successful implementation and completion of future SFT projects. Scaled-down model tests of SFTs serve as a crucial means for understanding the force characteristics of SFTs' structural systems. However, due to the complex water environment surrounding SFTs, it is challenging to model prototypical structures with perfect fidelity, so satisfactory test results often cannot be obtained. There are three primary challenges. First, SFT model testing is performed on a model consisting of a tunnel body, an anchor cable, and a soil body, and therefore requires the use of multiple materials, and it is difficult to maintain physical similarity between model materials and a prototype. Second, it is challenging to accurately replicate a prototype structure's detailed characteristics in a large-scale model, which hinders large-scale model testing. Third, calculating the dynamic boundary effects of the scaled-down model system requires the refinement of the model test results via fast and efficient numerical simulation techniques. The application of the CEL method in the calculation of hydrodynamic loads significantly overcomes some limitations of traditional methods. Conventional methods [PERSON] and [PERSON] [19] for calculating hydrodynamic loads typically assume that underwater structures are fixed to obtain external hydrodynamic loads. Then, using the known hydrodynamic loads, they calculate the structural response. For instance, the Morrison equation [20] assumes that the structure is stationary, while, in reality, the submerged floating tunnel undergoes certain relative displacements under the influence of hydrodynamic loads. This phenomenon is often challenging to accurately simulate using traditional methods. In the case of employing the CEL method, we can more precisely consider the interaction between the submerged floating tunnels and the surrounding water, achieving bidirectional fluid-structure coupling calculations. Compared to traditional methods like the Morrison equation, the CEL method is more in line with reality because it thoroughly considers the potential relative displacements of underwater structures under hydrodynamic loads. This characteristic enables the CEL method to provide more accurate and realistic numerical results, offering a more reliable basis for engineering designs and structural response analysis. Therefore, by adopting the CEL method, we not only address the limitations of traditional methods in considering structural displacements, but we also simulate hydrodynamic loads in conditions closer to real-world scenarios. This advantage highlights the significant innovation and practicality of the CEL method in underwater structure research.