Abstract
A computational model of simultaneous wave and sea current loads on tidal turbines was developed based on the rotor disc theory. Sea current profile and wave velocity components were defined in a cylindrical coordinate system positioned at the free surface. Tidal turbine loads were evaluated using the Modified Blade Element Momentum Theory by integrating the elemental thrust and torque values along the turbine blades. The analysis was performed in the time domain by considering various waves, hub heights, two and three turbine blades. An envelope of tidal turbine loads, which is the worst case scenario from the structural safety point of view, is presented. It provides forces and moments experienced by the tidal turbine in all three characteristic directions. An analysis of the flow velocity, elemental thrust and torque is provided as well as asymmetries in their respective distributions. The effects of the tidal turbine hub height and the number of rotor blades on the tidal turbine loads were investigated as well. A favorable increase in the power output for a tidal turbine situated closer to the sea surface is accompanied by an adverse substantial increase in tidal turbine loads, which is particularly exhibited for the pitch and yaw moments.