Research Of Coupled Model For Offshore Wind Turbine With Monopile Support Structure

For the design and research of support structure for offshore windturbine, dynamic analysis is very important. Developing a suitable windturbine model is the base for the dynamic response analysis of thestructure. There are two principles for modeling, one is to guarantee theaccuracy of the results, and another is to control the scale of the model.A monopile was designed for the NREL-5MW wind turbine. Thesteps and methods for structure modeling with ABAQUS were described.Three simplified pile-soil-interaction models-distributed springs model,apparent fixity model and coupled springs model-were derived. And thethree simplified models were compared with numerical model throughthe mode analysis. Results show that it’s effective to use these models forthe dynamic response analysis of wind turbine. With the distributedsprings model, the natural frequencies were caculated for the supportstructure. From the results, the mass and inerta moment of the turbine,and the added mass of entrained water have great effects on the structuremode, nevertheless the effect of gravity is very small. Finally, therealization of the coupled model was analysed. To build the coupledmodel of wind turbine, the wind, wave and current load were consideredsimultaneously with the ABAQUS user subroutine-DLOAD, and theinteraction between the structure response and the turbine load wasconsidered. With the coupled model, the dynamic response of themonopile was analysed under the steady wind and turbulent windrespectively. Results illustrate that the turbine load is the main load of themonopile, and for the fixed wind turbine when it is producing power, thedifference between the results of coupled model and uncoupled model is small. But when the dynamic response of the support structure isconsiderable, it’s important to use the coupled model.