Abstract
Marine currents are an important offshore source of renewable energy. A lot of effort is spent on the devel- opment of technology for, for example, electricity gener- ation from tidal currents. In the present paper, the perfor- mance of a vertical axis marine current turbine is exam- ined numerically under the variation of certain parame- ters.
The turbine is modelled with an in-house code, based on the double multiple streamtube model. Corrections are made due to a finite aspect ratio and tip losses for the blades. Published experimental data for the lift and drag coefficients of the blades for different Reynolds numbers are used in the model.
Structural integrity is a major concern of any under- water machinery due to the considerable hydrodynamic forces involved. Special attention is paid to the impor- tance of struts and related supporting structure for the turbine blades. As a rule of thumb, the efficiency of the turbine may be expected to rise with increased aspect ratio of individual blades. However, with leaner blades more support structure is required, which carries a cost in terms of a negative effect on efficiency. We study how the level of acceptable stress on a turbine blade influ- ences the total turbine efficiency depending on the num- ber of struts required to support the blade.