The Analysis On Aerodynamic Performance And Wake Vortex Of The Small Wind Turbine Under Yaw Flow

The wind turbines always operate in the atmospheric environment. The rotating plane of the wind turbine can’t be aligned to the wind direction in time because of changing velocity and wind direction. That makes the wind turbine often operate in the yaw condition, which leads to the reduction of the wind energy efficiency and the actual output power. So it is important to research the aerodynamic characteristics and wake characteristics of the wind turbine in yaw conditions.The new S type three blades axis wind turbine designed by the research team of Inner Mongolia University of Technology has been used in this paper. The diameter is 1.4 meter. The wind turbine model and calculation domain model have been established based on the DesignModeler module of software ANSYS. The unstructured mesh was divided by ICEM module. The turbulence model LES was used to achieve wind turbine wake simulation calculation based on the Fluent module and high frequency PIV was used to capture the tip vortex trace to explore the effect of yaw angle on aerodynamic characteristics and wake characteristics of the wind turbine.The main conclusions are as follows: With the increase of the yaw angle, the pressure coefficient of suction surface increases gradually, while the pressure coefficient of the pressure surface decreases, and the pressure difference on the surface of the blade decreases, which leads to the decrease of the wind power.The separation degree of the suction surface flow on the blade is different in each azimuth angle under yaw. The separation is the most serious in azimuth angle of 0°~120°, and the separation in azimuth angle of 240°~360° is not as serious as in azimuth angle of 0°~120°. However, the separation is slight in azimuth angle of 120°~240°. In addition, with the increase of the yaw angle, the separation degree of the suction surface flow on the wind turbine blade is increased, and the output power of the wind turbine is decreased.When the yaw angle is 0 °, the wind flows through the wind turbine plane vertically, lateral profiles of the normalized velocity in the wake is nearly symmetric. The velocity profile in the far-wake region have a Gaussian distribution. That means the flow field has become more and more gentle, and the velocity in the flow field is close to the main velocity. When the yaw angle is 30°, the velocity profile is no longer the characteristic of axial symmetry. One side of the wake is wider than the other side, this means that the wake recovery in one side is faster than the other side. When the yaw angle increases, the diameter of the wind turbine wake decreases. The radial displacement of the tip vortex center increases, but axial displacement decreases.