| The issue of energy is related to the survival and development of the entire human being.Due to the pollution of the environment by traditional energy sources,renewable cleanliness is gaining more and more attention from all countries in the world.The development of wind power in China is rapid.During the operation of the wind turbine,the blades of the wind turbine are subjected to the frictional resistance of the air,which causes a certain degree of flow loss.The utilization efficiency of wind energy is of great significance.First,the airfoil structure and its working principle are analyzed.With reference to the previous application of bionic microstructure,Flow field analysis of du21 airfoil by RNG k-s model in CFD simulation.Then the surface roughness sensitivity of the airfoil was studied,and it was found that as the roughness thickness value increased,the rise and drag coefficients showed a downward and upward trend,respectively,and the 0.5mm roughness thickness was between The median value,which distributes the roughness thickness at different positions of the airfoil,finds that the leading edge is more sensitive to roughness than other positions,and the pressure surface is less sensitive than the suction surface.Secondly,the DU21 airfoil is added with uniformly distributed micro structures for local modification and optimization.The effect of microstructures with different sizes,intervals,heights,angles and shapes on the total resistance of the airfoil under different working conditions is discussed.When the groove size is small such as 0.05mm,0.1mm and 0.15mm,drag reduction can be achieved under a variety of inflow speeds;with the increase of the interval size,the viscosity resistance gradually increases,and the pressure difference resistance gradually decreases When the decrease value of the differential pressure resistance is smaller than the increase value of the viscous resistance,the drag reduction phenomenon occurs;by changing the height of the groove,it is found that there is a minimum resistance value when h=0.075mm,which can be obviously compared with the changes of the five groove angles See the differential pressure resistance,and the minimum total resistance and differential pressure resistance when the angle is Oo;the shape of the microstructure has been modified many times,and it is found that the oval(groove)drag reduction effect is the best,and the maximum drag reduction rate can reach 3.62%.Orthogonal experiments are designed for the three-dimensional airfoil after stretching,which can achieve a maximum drag reduction rate of 3.41%.Compared with parallel,staggered,and unequal arrangements,it is found that the best is the parallel arrangement,under the condition of large angle of attack Underneath,the three-dimensional pit microstructure has a certain gathering effect on the separation vortex of the airfoil suction surface.Finally,the drag reduction mechanism of the drag reduction effect produced by the microstructure was studied,and it was found that a stable reverse vortex flow was formed inside the trench,resulting in indirect contact between the incoming flow and the wall surface,and the air cushion effect appeared,showing a similar The effect of "rolling bearing";regardless of the size of the groove,the vorticity increases with the increase of the incoming flow velocity,the vorticity is small or even close to 0 at the bottom of the groove;the turbulent kinetic energy and turbulent dissipation at the bottom The rate is very small,gradually approaching the wall surface from the bottom of the groove,the turbulent kinetic energy and turbulent dissipation rate also gradually increase,and the larger the size,the higher the extreme point;the verification of the dimensionless parameters shows that the Some results are not fully adapted to the airfoil. |
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