Hydrodynamic response of submerged floating tunnel in combined wave-current flows

Submerged floating tunnels are considered as feasible concepts for strait and estuary crossings where traditional tunnels and bridges face technical difficulties. An unknown factor is the environmental conditions that would allow safe, SFT construction and operation. This paper focuses on the effect of the environmental conditions like surface waves and ocean currents on the structural and dynamic behavior of the SFT. The effect of the hydrodynamics on the SFT has been covered by some studies in the literature. However, the increase of knowledge of especially the behavior of an SFT in a combined wave-current environment is of interest. In the research field of hydrodynamics around an SFT, there is a demand for more experimental studies. This study comprises of experiments on a rectangular cross section which was fixed with tethers, subjected to regular waves with varying wave heights and wave periods under different conditions of currents, submerged depth and inclined mooring line angle (IMA). The experiment results show that the SFT motion depends on the wave orbital motions mainly. When waves combined with the following currents, the currents will reduce the SFT motion by attenuation of the wave motion. The submerged depth and IMA are the two key parameters which are relevant to the SFT motion.