Research On Influence Of Wake Flow And Aerodynamic Noise Of Wind Turbine Under Yaw Flow

Shear wind, crosswind, gusty wind and so on are appearing in natural, which will affect the output and working life of wind turbines, and the aerodynamic noise on humans and the natural environment can not be ignored. Therefore, we should focus on the situation of output and aerodynamic noise under yaw flow.We have successfully established the horizontal axis wind turbine model with diameter 1.4m, airfoil NACA4415, it were researched characteristics on flow field and acoustic field under different yaw angles based on the numerical simulation, used IDDES turbulence model combined with FW- H equation. It got a part of the law on near wake flow field and acoustic field of wind turbines. It will offer certain research foundation for aerodynamic characteristics and aerodynamic noise of wind turbine under yaw in the future.The simulation results show that the maximum pressure region gradually decreased, the suction surface negative pressure region decreased on each layer with the increasing yaw angle. It also appeared that the pressure difference gradually decreased on the tip of blades, the ability to work diminished, caused the lift coefficient decreased, and eventually lead to the torque reduced, power decreased: under rated conditions, the output power was 205.51 W without yaw, it was decreased by 31% with yaw of 30°; The skew angle increased of wake flow, which lead to the axial velocity difference bigger and bigger: At the radial position 0.2R~0.3R and 0.9R~R, the axial velocity increased obviously, at the radial position 0.3R~0.9R, the axial velocity increases slowed down; The tip vortex and central vortex existed in wake flow, which spread to the downstream far away from the rotor, the vorticity amplitude decreased and disappear gradually.Tangential disturbance decided vortex, normal disturbance decided acoustic, both of them are movement and interaction in the gas form vortex sound interaction. To further study the aerodynamic noise under the yaw flow based on the research of wind turbine flow field, analysis the wind turbine sound sources, the RMS was bigger near the tip of blades, the maximum region gradually decreased with the increasing yaw angles; the noise energy is mainly concentrated in the low frequency of 400 Hz under different yaw angles, when the fundamental frequency corresponding to the total SPL of 109.67 dB, 109.42 dB, 109.02 dB and 108.45 dB; the SPL higher near axis line perpendicular to rotating rotator, decreased with increasing axial distance under different yaw angles; SPL decreased on the far side of sound sources face perpendicular to inlet with yaw angles increased, SPL increased on the near side of sound sources face with yaw angles increased; SPL still get the maximum on the tips of blades and minimum in the central axis under different yaw angles in the xoy and xoz plane, the SPL reduced on the corresponding position.For visual analysis and interaction analysis through L24(41×61), which obtained the yaw angle and speed interaction on the output power and aerodynamic noise was greater than the individual effect. Which provide evidence for the wind turbine achieving high performance, low noise, also provide a reference for wind turbine design.