| With the development of social economy,the ecological environment is deteriorating.In order to achieve sustainable development,it is imperative to achieve the goal of carbon dioxide emissions peak and carbon neutrality.As a sustainable,pollution-free clean energy,wind energy plays an indispensable role in the energy revolution.Wind turbine is a kind of power machinery that captures wind energy.Its operating state is affected by various factors such as the incoming wind speed and the performance of the wind turbine itself.When flowing through the wind rotor,the load on the blades affects the output power and working life of the wind turbine.The wake generated by the wind wheel will affect the output power of the downstream wind turbine.Thereby affecting the economic benefits of the entire wind farm.In recent years,wind farms with flat terrain in my country have been exhausted.The development of onshore wind farms has turned to mountainous terrain.The distribution of turbulence structure in mountainous terrain is complex,and the evaluation and utilization of wind resources are more difficult.Accurately analyzing the di stribution of wind resources in mountainous areas with different slopes can help us effectively predict the wake development of wind turbines and make a preliminary assessment of the operation status of wind turbines,which can help us to plan wind farms,micro-site selection,wind turbine deployment methods,aerodynamic design of wind turbines.Ultimately,maximize the benefits of wind farms.In this paper,the research object is the NREL5MW wind turbine,The Le MOS method is coupled with the large eddy simulation LES to numerically simulate the velocity and flow fields of the three slope terrain under the experimental conditions of the wind tunnel in the literature[1].By comparing the non-dimensional parameter acceleration ratio,it is verified that the artificial synthetic turbulence method is suitable for simulating different slope terrain.The distribution characteristics of the velocity and flow field in the shear and turbulent flow of the three slope terrains are analyzed.The topography in the wind tunnel experiment is expanded to the actual topography in 1:1000;then the Le MOS method is used in Under the turbulent flow conditions of 11.4m/s and 13.4m/s,study the relationship between the wake velocity recovery of wind turbines under three different slope terrains and the slope of the terrain,and the changes of aerodynamic parameters of wind turbines operating under different slope terrains feature.（1）Comparing the acceleration ratio between the numerical simulation and the wind tunnel experiment at the top of the mountain and the foot of the leeward surface,the numerical simulation can more accurately simulate the velocity and flow field characteristics under different slope terrain.By analyzing the acceleration ratio and the speed cloud diagram in the x,y,and z directions,it can be seen that the steeper the slope,the greater the acceleration ratio near the top of the mountain,and the more obvious the deceleration effect near the ground at the foot of the leeward surface;At the foot of the mountain on the leeward side,the three slope terrains only decelerated due to the combined action of terrain flow and turbulence;Compared with turbulent flow,under the same terrain,the wake velocity of the terrain under shearing flow is slower to recover.The steep terrain d X1 and d X2 form a recirculation zone near the ground at the foot of the leeward side,while the d X3 terrain does not have a backflow zone at the foot of the leeward side.Comparing the velocity distribution characteristics of the three slope terrains under the shearing flow and turbulent flow,the turbulent structure in the atmosphere has the most significant impact on the velocity flow field at the foot of the leeward side of the mountainous terrain,and the d X2 terrain velocity distribution has the largest difference.（2）Through the velocity cloud map and wake profile,the wake of the wind turbine that is located in the three slope terrains under two inflow conditions is analyzed.when inflow is under the condition of 11.4m/s,the wind turbine wake development in the DX1 terrain is weakly induced by the terrain.The lowest position before the expansion of the wake is near 1/2 of the height of the foot of the mountain on the leeward side,and the wake is developing backward.There is no flow phenomenon attached to the leeward side,In DX2 and DX3,the development of wind turbine wake is strongly induced by the topography of the leeward surface,and the wake completely adheres to the terrain and develops backward from the leeward surface.Under the condition of13.4m/s incoming flow,the development trend of wind turbine wake in DX1 is basically the same as 11.4m/s.In DX2 and DX3,the wake of wind turbines is disturbed by the flow around the terrain and the strong turbulence structure after the wind rotor,and the recovery of the wake is obviously earlier.compare the recovery of wind turbine wake velocity under two incoming flow conditions in three slope terrain,we can find that The wind turbine wake speed recovery in DX1 terrain has a low correlation with the incoming wind speed.At lower wind speeds,the impact of terrain on the wind turbine wake is more obvious.The slower the terrain slope is,the more unfavorable the recovery of the wake speed of the wind turbine;Under high incoming wind speed,when the wind turbine wake in the DX2 and DX3 terrain develops downwards from the wall,the strong turbulence structure after the wind rotor has a significant effect on the recovery of the wind turbine wake speed,The large-scale turbulent structure in the incoming flow has a much greater impact on the wake than the flow around the flow caused by the blocking effect of the terrain.The impact of the terrain on the wake is masked by the strong turbulence structure at high wind speeds.（3）Through spectrum analysis,statistical characteristics,wavelet analysis,and time domain analysis methods,We studied the change of wind turbine torque,flapwise and edgewise bending moment,as well as the relationship between the blade root bending moment and the Reynolds stress component at the blade root position,At an incoming wind speed of 11.4m/s,the average value of the wind turbine torque and flapwise bending moment in DX1 is the largest,followed by DX2 and DX3;At 13.4m/s incoming wind speed,the torque and blade root bending moment of wind turbines in DX1,DX2,and DX3 terrain are lower than 11.4m/s incoming flow,and DX1 reduces the most.The periodic fluctuation amplitude of aerodynamic parameters under 13.4m/s flow is greater than 11.4m/s,which significantly increases the fatigue load of the wind turbine and has a greater impact on the life of the wind turbine.According to the wavelet analysis of the blade root bending moment and the Reynolds stress component at the blade root position,We can know that The energy in the atmosphere is mainly provided by the large-scale vortex in the incoming flow.The energy of the large-scale vortex that develops stably through the wind rotor can be absorbed by the blade root and converted into the energy in the blade root bending moment.The rapidly developing unstable large-scale vortex is easy to cause The fatigue load of the wind turbine. |
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