Abstract: Aiming at the problem of aerodynamic performance reduction caused by increased drag on wind turbine blade under complex terrain and low wind speed conditions, taking 2.5 MW low wind turbine blade as the research object, combined with the non-smooth surface drag reduction theory of convex hull, the drag reduction characteristics of non-smooth blade were studied. Firstly, the structural parameters of variable convex hull were defined, and the size threshold of convex hull model was determined,sixteen groups of variable convex hull elements with different shapes were obtained by orthogonal experiments with four factors and four levels. Secondly, based on the analysis of low wind speed conditions, the variable convex hull non-smooth surface structure was arranged on the blade tail fin. Fluent software was used to carry out numerical simulation analysis on the drag reduction performance of the variable convex hull non-smooth blade under different low wind speed conditions, and the influence of different convex hull structural parameters on the drag reduction performance of the non-smooth blade was studied. Finally, the effect and mechanism of drag reduction on non-smooth surface of variable convex hull were studied. The results show that the maximum drag reduction rate of non-smooth blades is 5.89% under low wind speed. The primary and secondary parameters of convex hull affecting the drag reduction performance of blades are as follows: base radius R, height H, spacing D, vertex offset distance L; The non-smooth surface of the variable convex hull changes the shear stress distribution on the wall through the quasi-ordered structure. The ordered velocity and pressure gradient changes promote the flow of boundary layer fluid, and improve the drag reduction performance of the blade at low wind speed.
Key words: aerodynamic performance; nonsmooth blade; convex hull nonsmooth surface; drag reduction characteristics; orthogonal experiment