Numerical Research On Drag Reduction Aerodynamic Characteristics Of Blade For Verticalaxis Wind Turbine With Riblets

In recent years,the wind power industry has been booming with the country's vigorous promotion of clean energy.With its unique advantages,the vertical axis wind turbine has attracted wide attention both at home and abroad.Blade is the core component of wind turbine structure,and its good aerodynamic performance is the fundamental guarantee for improving the efficiency of wind energy utilization.Among them,the optimization of airfoil is the key factor to improve the aerodynamic performance of blades.The flow characteristics in the boundary layer near the airfoil determines the aerodynamic characteristics of the overall airfoil.Therefore,this paper mainly discussed the near wall area.This paper studied the common airfoil NACA0012 of the lift type vertical axis wind generator.Based on the bionics principle,the V-shaped ridge surface was arranged on the airfoil surface.By comparing the aerodynamic performance of modified front and rear airfoil with numerical simulation,the optimal optimization scheme was obtained and the mechanism of drag reduction was investigated.This paper mainly explored in the following aspects:(1)In order to ensure the calculation speed and quality,the airfoil mesh was verified independently.The suitable turbulence model was selected and the computational model was verified by experimental comparison and verification.The flow field conditions were set up to simulate the smooth airfoil NACA0012 and analyze the aerodynamic characteristics near the airfoil wall.Based on the working principle of vertical axis wind turbine blade,the basic research condition of this project was finally determined.(2)The ridge surface was arranged in the middle position and leading edge of the airfoil,and the two-dimensional numerical simulation of multi-group working conditions was carried out.Through the analysis of the ridge structure size of setting in the main parameters affecting the pneumatic performance(wind speed,angle of attack)concluded under the change of lift-to-drag trends,it was concluded that the main influence parameters,the optimal location and best ridge structure size.(3)The aerodynamic characteristics and flow mechanism of ridged surface were analyzed according to the change of lift to drag resistance.The effect of the secondary flow on the shear stress on the wall surface and the velocity distribution near the wall was observed with the opening size of the different ridges and the opening spacing.The variation trends of vorticity distribution and turbulent kinetic energy distribution were further investigated and compared with the smooth airfoil.The influence of the ridge structure on the aerodynamic characteristics of the whole airfoil was verified by analyzing the fluctuation trend of total resistance.Through calculation and analysis,the following conclusions are drawn as follows:(1)By contrastive analysis,the ridge structure with appropriate size in the center of the airfoil can get good drag reduction affect.The total resistance of the airfoil is the result of the combined action of pressure resistance and frictional resistance.Opening size s is larger,both of them increase at the same time;Open spacing a can't directly determine the effect of the two,only when the opening size s and the open spacing a match.The drag reduction effect is the most obvious,with the maximum drag reduction rated up to 35%.Among them,s-a has a good effect on the size optimization of the five groups of ridges of 0.5-0? mm,0.5-0.5? mm,1.5-1.5? mm,1.5-2.5? mm and 1.5-3.5? mm.It can improve the lift drag ratio and the airfoil aerodynamic performance.(2)There is no improvement in the aerodynamic performance of the airfoil with the ridge structure in the front edge of the airfoil.The leading edge of the airfoil is the key part of the flow velocity,which will affect the boundary layer of the whole airfoil wall.The lifting resistance ratio changes little with s=0.5? mm,a?1.5? mm,When the size increases further,the drag ratio decreases sharply.The uncertainty of the front roughness can cause the disturbance of the flow field near the airfoil surface to intensify,forcing the aerodynamic performance to deteriorate.Therefore,to control the damage degree of the leading edge is the key to ensure the aerodynamic performance of the airfoil.The results can provide a reference for the design of the resistance of balde in engineering.