Large eddy simulation for the effects of ground roughness and atmospheric stratification on the wake characteristics of wind turbines mounted on complex terrains

Abstract

The wake characteristics of wind turbine mounted on complex terrains are of great significance in wind energy utilization. The ground roughness and atmospheric stratification are two key factors for this issue and their coupling effect has not been fully studied before. In this research, the wake distributions of wind turbine mounted on two typical complex terrains and a real complex terrain are investigated using large eddy simulations and actuator disk model with rotation. The ground roughness and atmospheric stratification are simulated by adding source term in the governing equations of fluid dynamics to generated temperature gradient and vegetation canopy. It is found that the effects of ground roughness and atmospheric stratification on the wake of wind turbine are superimposed or counteracted depending on the shape of complex terrain. The presence of atmospheric stratification reduces the power of wind turbine drastically by more than 40% and the rough ground causes a small decrease in the power of wind turbine on typical complex terrains. For the multiple wind turbines on a real terrain with rough ground, the influence of atmospheric stratification on the wake characteristics and power production of each wind turbine strongly affected by the micrositing of wind turbines. The usual practice in industry of multiplying the oncoming wind profile by the turbine power curve overestimates the power production of wind turbines on complex terrains with atmospheric stratification by up to 670% compared with the numerical results.