| With the increasing demand for energy,the traditional energy structure based on fossil fuel is increasingly unable to meet the needs of development.Wind energy,which has the advantages of abundant resources,clean and renewable,has attracted increasing attentions.Wind turbines are the main equipment that utilizes wind energy.When the incoming flow passes through the rotating wind turbine,part of the energy is absorbed.The wind speed will reduced by a certain amount,and the turbulence will increase,which is called wake effect of wind turbine.The wake effect will affect the power generation and operating status of the wind turbines arranged downstream.Compared with flat terrain,due to the ups and downs of complex terrain,the wake of the wind turbine and the flow around the terrain may has interference,and the complexity of the downstream flow field may be greatly increased.In order to study the flow interference between wind turbines and terrain under complex terrain,numerical simulations and different wind turbine modeling methods are used to simulate the flow of a single wind turbine under flat terrain and typical hilly terrain.The wind turbines are placed at different positions in the flow direction of the typical terrain,and the wake fields of the wind turbines calculated by the three methods of full geometric modeling,actuator disc and actuator line are compared.The characteristic of wind field under the joint influence of wind turbines and terrain is analyzed.The main research contents are as follows:(1)The model of actuator disc and actuator line was developed using UDF.Three models are used to study the wake velocity distribution and wake vortex structure of wind turbines under flat terrain.The comparison results show that the average wake velocities obtained by the three models are in good agreement.Due to the different volume force distribution,the wake structure of the actuator disc is single hump-shaped,and the actuator line is similar to the wake structure of the blade direct modeling method.The intensity of the mechanical turbulence produced by the actual blade makes the blade direct modeling method more perturbation of the velocity in the near-wake region.The actuator line has a large volume force distribution range,thus it also has a strong blocking effect on the incoming flow,and could produce a more obvious wake vortex structure.(2)The related influence of wind turbine wake and the flow around the terrain under the typical complex terrain-hilly terrain is studied.Under the given inlet conditions of wind shear,the wake velocity distribution and wake vortex structure calculated by the three models are compared and analyzed.Due to the larger volume force distribution range,the wake structure of the actuator line method is closer to the ground.Under the coupling effect of the tip vortex and the terrain-induced vortex,the breakage and dissipation of the wake vortex structure is more severe.(3)By arranging wind turbines at different locations around the hills,given the shear inflow conditions,the interference phenomenon of the terrain flow and the wind turbine flow at different locations is studied.The results show that when the wind turbine is placed in front of the mountain,the greater the distance between the wind turbine and the hill,the more obvious the flow separation behind the mountain;the higher the height of the hill,the more obvious the flow separation behind the mountain.Through the comparative study of the three wind turbine modeling methods,it is found that the actuator line method can reflect the details of the flow field,saves more computing resources than the direct blade modeling method.actuator line method is more applicable to the interference problem of wind turbine wake and flow around terrain studied in this paper.The current research on the wind turbine wake and its related influence on the flow around complex terrain provides theoretical support for the micro-site selection and optimization of wind farms with complex terrain. |
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