Numerical comparison of natural frequencies with vortex separation frequencies of a laboratory model of a wind turbine blade

In this article, a numerical study of the vortex shedding frequencies in comparison to natural frequencies of the wind turbine blade was carried out. Geometry of the model was acquired through reverse engineering of an already existing laboratory model of the blade. A three-dimensional modal analysis of the blade was conducted using the finite element method and the first six natural frequencies were obtained. Following the modal analysis, two-dimensional numerical airflow simulation was conducted for air velocities of 2 m/s, 18 m/s, 36 m/s and 55 m/s. Numerical study has shown that at speeds of 55 m/s and 36 m/s the von Karman vortex separation frequency is near 400 Hz, which is close to the fifth and sixth obtained natural frequency of the blade. At an air flow of 18 m/s the Karman vortex separation frequency is not near any natural frequency of the blade model and it should be considered safe. Obtained vortex shedding frequencies revealed several hazardous airflow speeds at which vibrations will occur and consequently reduce the lifespan of the wind turbine blade.