Interaction Between Wind Turbine And Turbulent Flow In The Neutral Atmospheric Boundary Layer

In wind farms,the performance and structural dynamics of the wind turbine are largely affected by the atmospheric and the wake of the upstream wind turbine.Incoming flows not only interact with wind turbines,but also affect the propagation and development of wakes,which in turn affect downstream wind turbines.In this paper,the wind turbine flow field with uniform flow conditions and the neutral atmospheric boundary layer is simulated by the combination of large eddy simulation and actuating line model to study the interaction between turbulence and wind turbine.Firstly,for understand the spatio-temporal evolution of the wind turbine wake,actuator line model and large eddy simulation was combined to establish the wind turbine flow field,and the analysis method based on wavelet transform.The study found that with the increase of the distance from the rotor,the average velocity of each measurement point in the wake decreased first and then gradually increased,the amplitude of the velocity fluctuation showed a decreasing trend;within 7 times of the diameter after the wind turbine,the velocity curve has a pronounced periodicity,reflecting the shedding vortex passing frequency of 1.8Hz,which is twice the rotation frequency of the wind turbine.The frequency range of the tip vortices at the 1 times diameter measurement point after the rotor is 0.78~25 Hz,the time for the formed vortex tube to pass the measurement point is approximately 0.32 s,the diameter of the vortex tube is approximately 1.83 m.A low-frequency turbulent structure of 0.15~0.78 Hz appeared at the three times diameter measuring point;the frequency range of the tip vortex at the seven times diameter measuring point was 1.56~25Hz,which is greatly reduced compared with the tip-vortex frequency range before the seven times diameter measurement point.At the eight times diameter measurement point,the vortex tube shape of the tip vortex similar to the near wake region disappears;the tip vortex at the nine times diameter measurement point is almost completely dissipated.Secondly,for a single wind turbine under uniform flow,wavelet is used to analyze the speed of the center point of the rotor and the load of the rotor.The results show that there is a correspondence between the speed of the center point and the load,and the speed of the center point of the rotor is the result of wake induction,which reflects the influence of the wake on the load.For two wind turbines with different distances arranged in series,the average load of the wind turbine in the wake is found to be less than the upstream wind turbine.The root mean square of the load is much larger than the upstream wind turbine and increases with the distance from the upstream wind turbine.The root mean square of the downstream wind turbine load increases gradually.The wind turbine load in the wake is studied by discrete wavelet analysis: frequency ranges of the wind turbines in the wake have similar responses to the incoming are 6.5~25 Hz and 0.781~1.562 Hz,with different responses is of 1.565~3.125 Hz.Wind turbines with diameters of 3 to 7 diameters have a similar response to the incoming flow in 3.125~6.25 Hz,and wind turbines with a distance of 10 times the diameter have different responses to incoming and outgoing flows.Finally,the interaction between turbulence and wind turbines in neutral atmospheric boundary layer was studied.Based on the data provided by experiments as the basic parameters of the simulation,the wind turbine flow field in the neutral atmospheric boundary layer was simulated and the accuracy of the simulation results was verified.The turbulent flow gradually becomes stronger from the front of the rotor to the rear;the turbulence structure at the plane of the rotor shows a smaller-scale turbulence structure than other locations.The turbulence structure at one times diameter after the rotor is basically same as the front of the rotor,which the turbulence moves with large-scale structure,but the turbulence energy after the rotor is higher than the front of the rotor.The wavelet analysis of the turbulence and the load shows the interaction of the turbulent structure with the rotor.In the period of low turbulence energy at the front of the rotor and at the center of the rotor,the load of the rotor is low;when the turbulence energy is high,the load is high.The turbulence energy of inflow transfers to the wind turbine,and drive the wind turbine rotates,while the wind turbine acts on the turbulence to cause a higher frequency turbulence structure,which in turn acts on the wind turbine to generate a higher frequency wind turbine load.By comparing multiresolution analysis of the two points at the center and the tip of the wind turbine with load of the blade root using wavelet,it was found that the low-frequency load of the wind turbine is caused by the low-frequency turbulent flow,and the high-frequency load is related to the tip vortex.Through correlation analysis,it was found that there is a good correlation between turbulent turbulence with horizontal direction and load.