Dynamic Behaviour of Cylindrical Shells Immersed in Fluid Media

Abstract

The Submerged Floating Tunnel (SFT) emerges as an innovative and futuristic alternative for underwater transportation, offering enhanced connectivity across deep and wide water bodies while preserving the natural beauty and functionality of marine ecosystems. Its development represents a pioneering solution in civil and marine infrastructure, integrating advanced structural and hydrodynamic principles. The structural design of an SFT is inherently a multidisciplinary challenge, involving elements from structural engineering, fluid mechanics, hydrodynamics, marine engineering, and finite element analysis (FEA). This study investigates the dynamic behaviour of a submerged cylindrical shell, simulating an SFT, under the influence of underwater explosion loading. Using advanced simulation tools within ANSYS software, multiple design configurations were analyzed to evaluate the tunnel\'s structural response in terms of deformation and stress distribution. By systematically varying tunnel length, tether spacing, and tether angle, this project aims to identify optimal configurations that minimize damage and enhance the stability of SFT systems under extreme dynamic loading conditions.

Introduction

This research investigates the structural behavior of a Submerged Floating Tunnel (SFT) subjected to dynamic loads from underwater explosions using ANSYS simulations. The study focuses on how key design parameters—tunnel length, tether spacing, and tether inclination angle—influence the tunnel’s dynamic response, including deformation, stress distribution, and stability.

The SFT, an innovative underwater crossing structure, is vulnerable to dynamic forces due to its submerged, flexible design. Prior studies on submerged cylindrical structures provide a foundation for understanding fluid-structure interactions and failure mechanisms under shock loading.

The methodology involved creating detailed 3D ANSYS models of the tunnel, tethers, surrounding water, and explosion source, incorporating fluid-structure interaction and transient dynamic analysis. Twelve models varying tunnel length (200 m and 500 m), tether spacing (50 m and 100 m), and tether angles (30°, 45°, 60°) were tested under identical blast conditions.

Results showed that longer tunnels are more flexible but somewhat more resistant to localized deformation, wider tether spacing leads to higher displacements, and steeper tether angles reduce lateral displacement but increase axial tension. The best performing design balanced these factors with a 500 m tunnel, 50 m tether spacing, and 45° tether angle, achieving optimal stress distribution and minimal displacement.

Conclusion

The dynamic response of a Submerged Floating Tunnel subjected to underwater explosion loading was successfully modeled and analyzed using ANSYS. The study highlights the importance of design parameters in determining structural stability under extreme conditions. Key conclusions include: 1) Doubling tether spacing leads to substantial increases in displacement — up to 80.4% in Z-direction and 53.8% in Y-direction. 2) Increasing TIA generally reduces Z-direction displacement but has a non-linear effect on Y-direction due to tether dynamics. 3) Model 8 proved to be the most efficient configuration, offering optimal balance between structural rigidity and flexibility. This research contributes valuable design insights for future SFT applications and underscores the need for comprehensive dynamic analysis in early design stages.

References

[1] Feng, J., Wu, Y., Xue, J., & Lin, J. 2024. Dynamic stability analysis of laminated cylindrical shells considering fluid–structure interaction. Composite Structures, 340, 118183. Available online 4 May 2024. 2. [2] Macapagal, V. P., Kwon, Y. W., &Didoszak, J. M. 2024. Cylindrical single wall and double- wall structures with or without internal water subjected to underwater shock loading. Heliyon. 3. [3] Zhang, S., Li, T., Zhu, X., & Han, Y. 2023. Vibration and critical pressure analyses of functionally graded combined shells submerged in water with external hydrostatic pressure. Applied Mathematical Modelling, 120, 246–266. 4. [4] Geers, L., Hunter, S., 2022. An integrated wave-effects model for an underwater explosion bubble. J. Acoust. Soc. Am. 111 (4), 1584–1601. 5. [5] Zhang, S., Li, T., Zhu, X., Yin, C., & Li, Q. 2022. Far field acoustic radiation and vibration analysis of combined shells submerged at finite depths. Ocean Engineering.”

Copyright

Copyright © 2025 Mrs. Pallavi M. Khatavkar, Mr. Om U. Chavande. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.