Experimental study on auto-parametrically excited heaving motion of a spar-buoy
Experimental studies were carried out to investigate the possibility of utilization of autoparametrically excited oscillation based on the Mathieu-type instability. For the simplicity, the subject is limited to the heaving motion of a spar-buoy type point absorber. The device consists of an inner cylinder and 12 outer cylinders. Each outer cylinder is equipped a movable floating column controlled by a ball screw mechanism and the buoyancy of the outer cylinders can be dynamically changed to induce the Mathieu-type instability. Based on results of the numerical simulation and the model tests, the possibility of utilization of auto-parametrically excited oscillation for WEC was discussed. Furthermore, the effect of the proposed control system in irregular waves was investigated.