One of the advantages of floating offshore wind turbines (FOWTs) is that they can be designed to be easily wet towed and installed to reduce the cost of offshore construction. In this paper, a fully coupled towing system numerical model is established for a novel 10 MW FOWT concept, namely, a submerged floating offshore wind turbine (SFOWT) to investigate the towing performance. Firstly, the numerical simulation is validated by comparison with model experiment results. Then, a series of numerical simulations are conducted to predict and compare the towing performance for a three-column SFOWT (TC-SFOWT) and a four-column SFOWT (FC-SFOWT) under different wave conditions. The results show that the two forms of SFOWT have good towing performance when the significant wave height is less than 5 m, which is the maximum wave height for the allowable towing condition. The FC-SFOWT shows relatively better performance in heave motion and roll motion, but the towing force is relatively larger compared with the TC-SFOWT under the same condition. When the significant wave height is 5 m, the maximum values of heave motion, pitch motion, and roll motion of the TC-SFOWT are 2.51 m, 2.14°, and 1.38°, respectively, while they are 2.25 m, 2.70°, and 1.21°, respectively, for the FC-SFOWT. Both the roll motion and the pitch motion are satisfied with the requirement that the roll and pitch are less than 5° during the towing process. The mean towing force of FC-SFOWT is 159.1 t at the significant wave height of 5 m, which is 52.8% larger than that of TC-SFOWT. The peak period mainly influences the frequency where the response peak appears in power spectra. The findings in this paper could provide some guidelines for wet towed operations.

In order to achieve the purposes of the transportation and installation of the integrated wind turbine with the mono-column composite bucket foundation, an integrated floating platform has been developed. Taking the integrated towing process of the multi-body coupling system as the research object, a model test with a scale ratio of 1:80 is designed. The influences of environmental factors such as significant wave height, wave period, and the wave incident angle on the motion response of the integrated wind turbine and the floating platform during the floating-transport process, the pressure inside the compartment, and the towing cable force have been studied. The research findings are as follows: (1) Wave height and wave period have a great influence on the integrated wind turbine and the floating platform. With the increase in wave height and wave period, the motion response of the integrated wind turbine and the floating platform increases, the air pressure fluctuation in the bucket foundation compartment becomes more and more intense, and the towing cable force required for towing also increases and fluctuates more violently. (2) When the wave incident angle changes from 0° to 45°, the pitching motion frequency of the integrated wind turbine significantly increases, the overall fluctuation of the compartment pressure in the bucket foundation compartment decreases, the motion response of the floating platform becomes larger, and the towing cable force required for towing also increases accordingly.