Analysis Of Acoustic Characteristics Of Wind Turbine Wake Under Dynamic Inflow Condition

Wind turbines operate in an extremely complex and changeable unsteady natural environment.As one of the key factors of the wind turbine working environment,wind conditions not only determine the output power of the wind turbine,but also cause serious noise pollution problems to a certain extent.Noise pollution has a great impact on the living and working environment of nearby residents.Therefore,with the large-scale construction of wind farms,the noise pollution generated by wind turbines has become a common concern,and the generation mechanism and noise reduction of aerodynamic noise of wind turbine blades The method has subsequently become a hot spot in the optimal design of wind turbine blades.However,in the actual operation of wind turbines,the dynamic changes of natural wind speed cannot be accurately predicted,and the development of high-speed flow field monitoring equipment is lagging,making experimental research difficult to carry out.Therefore,the simulation calculation method provides a certain reference basis for analyzing the aerodynamic noise characteristics of the wind turbine wake under dynamic wind load.This paper takes distributed horizontal-axis wind turbines as the research object.According to the characteristics of natural wind speed changes in the experimental base and the actual operating conditions of the wind turbines,three typical dynamic inflow functions of gusts,gradual winds,and turbulent winds are fitted.The user-defined UDF realizes the dynamic change of speed and serves as the entrance boundary condition.At the same time,the unsteady calculation model under different variable wind conditions is established,and the Fluent computing platform is used to analyze the development law of the flow field and sound field in the near wake area of the wind wheel.First,analyze the pressure pulsation on the blade surface under different wind conditions,extract the pressure pulsation data at each monitoring point,and find that the time domain diagrams under each inflow condition show periodic fluctuation characteristics,and the pressure pulsation peaks are different after loading the dynamic inflow.The increasing trend of the degree,the disturbance wind has the greatest impact on it.The pressure pulsation peak at the middle position of the blade is obviously higher than the tip and root of the blade,and the pressure pulsation value behind the blade is larger than that in the front of the blade.Secondly,by studying the acoustic radiation propagation characteristics of the wind wheel wake,it is found that the rotating noise of the wind wheel before and after the dynamic wind load is mainly concentrated on the fundamental frequency and its multiples,and the noise value is the largest at the fundamental frequency.The sound pressure level shows a decreasing trend with the increase of the axial distance and reaches the maximum near 0.5m;the sound energy along the radial direction at the same axial position under different variable wind conditions shows a law of first increasing and then decreasing,in which the disturbance The wind has the greatest impact on it,and the peak sound pressure level gradually approaches the blade tip in the radial direction with the increase of the axial distance.On the basis of the above research,we further analyze the change characteristics of the vorticity field under dynamic wind load.By observing the trend of the vorticity curve at different positions,it is found that the vorticity is roughly symmetrically distributed with respect to the wake center,and the vorticity peak position is consistent with the above sound The pressure radiation law is consistent,and the vortex sound theory is also better used to reveal the mechanism of vorticity changes on aerodynamic noise.In this paper,by loading the dynamic inflow function,the simulation calculation of the aerodynamic noise characteristics of the wind turbine under the dynamic change of wind speed is realized.At the same time,it better fits the operating characteristics of the wind turbine in the actual work.The research on the aerodynamic noise propagation of the wind turbine has important theoretical significance.And engineering application value.It provides a certain theoretical basis for the noise reduction treatment of wind turbines and the optimal design of the blade structure.