Preliminary Investigation of Power Output of Two Typical Two-Turbine Tidal Current Systems

The hydrodynamic interaction between a stand-alone tidal current turbine and the incoming flow through it affects the power output of the turbine. Similarly, the hydrodynamic interaction between two tidal current turbines is expected to affect the power output of the two turbines. In this situation, we called the two turbines a two-turbine system. Turbine designers, especially those former naval architects, who worked on a two-propeller system before, strongly hold that the two-turbine system is one of the more cost-efficient formats of extracting energy from tidal current. Consequently, the relationship between hydrodynamic interaction and the power output of the two-turbine system is receiving broad attention, although it has not been systematically studied. In this paper, the parameters of the design of a two-turbine system are identified and nondimensionalized and two typical system layouts are given: canard layout and tandem layout two-turbine systems. By using the recently developed numerical method for simulating unsteady flow and tidal current turbine, i.e., DVM-UBC, a new numerical model for predicting the power output of a two-turbine system is developed. The power outputs of two-turbine systems of these two typical layouts are analyzed. It is noted that the total power output of a two turbine system with optimal configuration can be 25% higher than that of two stand-alone turbines. Also, we find that the power output of a canard layout two-turbine system is higher than that of a tandem layout two-turbine system.