Computational Fluid Dynamics (CFD) Investigation of Wind Turbine Nacelle Separation Accident over Complex Terrain in Japan

We have developed an unsteady and non-linear wind synopsis simulator called RIAM-COMPACT (Research Institute for Applied Mechanics, Kyushu University, COMputational Prediction of Airflow over Complex Terrain) to simulate the airflow on a micro scale, i.e., a few tens of km or less. In RIAM-COMPACT, the large-eddy simulation (LES) has been adopted for turbulence modeling. LES is a technique in which the structures of relatively large eddies are directly simulated and smaller eddies are modeled using a sub-grid scale model. In the present study, we conducted numerical wind diagnoses for the Taikoyama Wind Farm nacelle separation accident in Japan. The simulation results suggest that all six wind turbines at Taikoyama Wind Farm are subject to significant influence from separated flow (terrain-induced turbulence) which is generated due to the topographic irregularities in the vicinity of the wind turbines. A proposal was also made on reconstruction of the wind farm.