Currently, floating wind turbines (FWTs) may be the more economical and suitable systems with which to exploit offshore wind energy in deep waters. Among the various types of floating foundations for offshore wind farms, a tension leg platform (TLP) foundation can provide a relatively stable platform for currently available offshore wind turbines without requiring major modifications. In this study, a new multi-column TLP foundation (WindStar TLP) was developed for the NREL 5-MW offshore wind turbine according to site-specific environmental conditions, which are the same as the OC3-Hywind (NREL) conditions. The general arrangement, main structure and mooring system were also designed and investigated through hydrodynamic and natural frequency analyses. The complete system avoids resonance through the rotor excitations. An aero-hydro-servo-elastic coupled analysis was carried out in the time domain with the numerical tool FAST. Statistics of the key parameters were obtained and analysed and comparisons to MIT/NREL TLP are made. As a result, the design requirements were shown to be satisfied, and the proposed WindStar TLP was shown to have favourable motion characteristics under extreme wind and wave conditions with a lighter and smaller structure. The new concept holds great potential for further development.

Deep-water regions often have winds favorable for offshore wind turbines, and floating turbines currently show the greatest potential to exploit such winds. This work established proper scaling laws for model tests, which were then implemented in the construction of a model wind turbine with optimally designed blades. The aerodynamic, hydrodynamic, and elastic characteristics of the proposed new multi-column tension-leg-type floating wind turbine (WindStar TLP system) were explored in the wave tank testing of a 1:50 scale model at the State Key Laboratory of Ocean Engineering at Shanghai Jiao Tong University. Tests were conducted under conditions of still water, white noise waves, irregular waves, and combined wind, wave, and current loads. The results established the natural periods of the motion, damping, motion response amplitude operators, and tendon tensions of the WindStar TLP system under different environmental conditions, and thus could serve as a reference for further research. Key words: floating wind turbine, model test, WindStar TLP, dynamic response

The Eulerian–Eulerian method is efficient when dealing with liquid–solid slurry flows containing a large number of particles, but its reliability relies on an accurate description of liquid–particle interaction for which numerous interphase drag models have been proposed. However, the performance of these models has not been systematically evaluated when applied to slurry flows. In this study, slurries in horizontal pipes under various flow conditions are simulated using the Eulerian–Eulerian method. Six commonly used drag models, such as the Schiller–Naumann, Wen–Yu, Gibilaro, Gidaspow, Syamlal–O'Brien, and Huilin–Gidaspow models, are assessed based on their predictions of streamwise velocity, secondary flow, solid concentration, and liquid turbulent kinetic energy. Under normal operations, all models provide similar streamwise velocities and secondary flow patterns. However, the Schiller–Naumann model presents an intensified secondary flow and a flattened solid concentration profile. All models perform poorly for the solid concentration distribution, which may be corrected by considering the overall mean solid concentration. Additionally, the Wen–Yu model, which has previously been thought applicable only for dilute systems, behaves very closely to the Gidaspow model, which is usually recommended for dense fluidized beds.