AN EXPERIMENTAL STUDY OF YAW MOTIONS OF SPAR-TYPE FOWT

The offshore wind energy is one of the most important renewable energy resources which can cover worldwide energy demand. The wind turbines are devices that canconvert wind energy to electrical energy. Noting that the wind energy is stronger on offshore regions, the floating offshore wind turbines (FOWTs) can be a proper choicefor generating electricity. Therefore, analyzing various forces on these devices including hydrodynamic and aerodynamic forces can be vital in the FOWTs designprocess. Existence of rotating blade in the FOWTs system makes the gyroscopic effect as a substantial parameter in the hydrodynamic studies. If the rotation of turbine blades around an axis leads to the oscillation of the system around another axis, these movements will make the system oscillate around the third axis which is perpendicular to the previous axes; this effect is called the gyroscopic effect. As an example, if the spinning turbine rotor has an angular momentum (torque) around the surge axis and this motion results in platform oscillation in pitch direction, the spinning rotor creates a new component of angular momentum yaw. This new component of angular momentum may either enhance or decrease the yaw motion of platform. Similarly, initial yaw motions can also induce torque and motions in pitch.