Numerical and Experimental Analysis of the Motion Response in a Combined Wind and Wave Energy Platform According to Incident Wave Direction

초록

This study investigates the effects of the direction of incident waves on the motion of a Floating Offshore Wind Turbine (FOWT) when multiple Wave Energy Converters (WECs) are attached. For this purpose, the hydrodynamics program ANSYS AQWA, based on potential flow and boundary element methods, was utilized. The numerical analysis utilized a sub-platform model for the FOWT, with a depth of 89.6 m, a diameter of 17.92 m, a length of 61.44 m, and a draft of 51.2 m. The wind turbine and RNA used the NREL's 5-MW Reference Wind Turbine model, and the mooring lines employed an inclined taut mooring method. The tower applied was the 77.6 m tower used in NREL's OC4 project. The WECs were cylindrical wave energy converters, each with a diameter of 10.24 m, a draft of 7.68 m, and a length of 12.8 m, placed at 90° intervals around the FOWT. The FOWT and WECs were connected via hinge conditions. The wave conditions were set at intervals of 0.5 sec or 1 sec within a period range of 8 sec to 16 sec. The wave height was a regular wave of 1.28 m, and the incident wave angles were set at four different angles (0°, 15°, 30°, 45°) at 15° intervals. The motion of the combined wind-wave energy platform under each condition was calculated. The experimental model was scaled down to approximately 256:1 to fit the size of two-dimensional wave tank in Inha University. The model specifications were a cylindrical model with a diameter of 8 cm, a length of 24 cm, and a draft of 18 cm, with the wind turbine also scaled down and mounted on top of the platform at the same ratio. The incident waves used periods of 1/16 of those used in the numerical analysis, ranging from 0.5 sec to 1.2 sec, and a wave height of 1 cm.