This study deals with the hydro-aero-mooring coupled dynamic analysis of a new offshore floating renewable energy system, which integrates an offshore floating wind turbine (OFWT), a wave energy converter (WEC) and tidal turbines. The primary objective is to enhance the power production and reduce the platform motions through the combination of the three types of renewable energy systems. Simulation results show that the combined concept achieves a synergy between the floating wind turbine, the wave energy converter and the tidal turbines. Compared with a single floating wind turbine, the combined concept undertakes reduced surge and pitch motions. The overall power production increases by approximately 22%e45% depending on the environmental conditions. Moreover, the power production of the wind turbine is more stable due to the reduced platform motions and the combined concept is less sensitive to the transient effect induced by an emergency shutdown of the wind turbin

This study focuses on the hydrodynamic interaction between two or three human swimmers in competitive swimming. Although the swimming performance of a single swimmer has been widely examined, studies on the interaction between multiple competitive swimmers are very rare. Experiments showed evidence that the drag of a swimmer could be modified by the existence of the other adjacent competitors (Chatard & Wilson. 2003Med. Sci. Sports Exerc.35, 1176–1181. (doi:10.1249/01.MSS.0000074564.06106.1F)). The following questions arise: (1) what mechanism determines the interaction; (2) which position experiences drag reduction or drag increase; (3) how much can drag be reduced or increased in a formation? According to the authors' knowledge, such questions have not been addressed by any published literature. Therefore, the main purpose of this study is to find the mechanism of the hydrodynamic interaction between human swimmers and to quantify this interactive effect by using a steady potential flow solver. The free-surface effect was fully taken into account in our calculations. We firstly calculated the wave drag of a swimmer swimming solely in an open swimming pool. Then we calculated the wave drag of the same swimmer when he/she swam in the wake region of one or two leading swimmers. The results showed that the hydrodynamic interaction made a significant contribution to the drafter's wave drag. By following a leading swimmer, a drafter at wave-riding positions could save up to 63% of their wave drag at speed of 2.0 m s⁻¹and lateral separation of 2.0 m. Particularly, when a drafter is following two side-by-side leaders, the drag reduction could even be doubled. To the authors' knowledge, this study is the first to demonstrate that the hydrodynamic interaction between human swimmers can best be described and explained in terms of wave interference effect on the free water surface. When the wave cancellation effect is observed, the wave drag of a drafter could be minimized, and this wave cancellation effect can be achieved only when the drafter is in a wave-riding position.