Dynamic Responses And Fatigue Characteristic Analysis Of The Offshore Wind Turbine Tower Under Combined Wind And Wave

Aerodynamic loads and structure of onshore or offshore wind turbines were analyzed. For onshore wind turbines, the dynamic response of the 1.5MW variable speed pitch regulated wind turbine cylindrical tower caused by unsteady aerodynamic loads was analyzed using the finite element analysis method. Dynamic characteristics of the tower was calculated numerically and the influence of the nacelle and rotor weight on the tower natural frequency was tested. The relationship between aerodynamic loads especially unsteady ones on the cylindrical tower and Reynolds was studied. According to the aerodynamic loads, the dynamical displacements of the tower top were calculated along the crosswind and the downwind under the over-critical and supercritical conditions. The results show that unsteady aerodynamic loads are important reasons which causing a tower vibration and the dynamic research of a tower is far more important than the static research.Complex load conditions of offshore wind turbine cylindrical tower were analyzed; accordingly, under the combined random wave and wind loads, the dynamic response of numerical analysis methods for towers was researched; after applying the Palmgren Miner linear damage rule ,fatigue properties and a safety life estimation method of concrete towers were achieved. On the basis of the linear wave theory, two-dimensional linear wave theory has been enriched and developed into three-dimensional linear wave theory after the coordinate transformation, in order to adapt to the three-dimensional space analysis and calculation; accordingly, the plane wave Morrison forces has been developed into space wave forces system; and the appropriate correlation of wind and wave loading was checked. Finally, flexibility 3D beam element with 5-DOF was designed, and the fatigue load spectrum, such as the tower node displacement, velocity, acceleration, etc. were solved by the non-linear wave analysis procedures and fatigue life calculation procedures; followed by rainflow counting, damage criteria and fatigue life estimation method is proposed. Examples show that: the work of the entire marine wind turbine system aeroelastic analysis, wind-tower vibration analysis and fatigue life analysis provide a useful analytical method.