Abstract:In order to get closer to the actual working conditions of wind turbines, four typical wind conditions, namely, normal vertical wind shear, extreme vertical wind shear, extreme running gust and extreme wind direction change, are selected to program the dynamic incoming flow through UDF. Based on FLUENT, sliding grid technology and RNG, the effects of dynamic incoming flow and tower shadow effect on the downstream wake characteristics of wind turbines are studied. The results show that the dynamic inflow compiled by UDF is in good agreement with the theoretical value, which verifies the correctness of UDF. Under the dynamic inflow conditions, the power output of wind turbines fluctuates in different degrees, and the wake structure changes obviously from blade root to blade tip. The existence of tower shadow effect decreases the torque and power of wind turbines, makes the lift of tower surface change sharply, and fatigues the tower. Life expectancy has a negative impact. The results of numerical calculation have important reference value for the structural design of wind turbine units and the array analysis of wind farm units. |