Abstract: As a new concept of tidal current power generation device, the shaftless rim-driven ducted (SRD) turbine has many advantages and a wide application prospect. We apply a computational fluid dynamics (CFD) method to simulations and a comparative study of this type of turbine and the conventional shaft ducted turbine, focusing on the differences in hydrodynamics between these two ducted turbines and the influence of shaft diameter ratios on the SRD turbine. The results show that in a certain range of shaft diameter ratios, the SRD turbine has a higher output power and lower axial thrust than those of the shaft ducted turbine. However, the fluctuation amplitudes of its instantaneous power output and axial thrust are slightly larger, and they further increase with a decreasing shaft diameter ratio. We find that for the SRD turbine with a swept gap of a certain size, pressure will force water to "leak" through the gap forming an axial jet. This will result in a significantly higher wake recovery rate that is further accelerated with a decreasing shaft diameter ratio.

Key words: tidal power, shaftless rim-driven ducted turbine, hydrodynamic performance, numerical simulation