Dynamic evolution of wind-sand erosion on the straight wing section of S809 and its effect on aerodynamic performance

When the wind turbine operates in the wind-sand environment, the sand particles will cause erosion and wear on the surface of the wind turbine blades, which will result in morphological changes and lead to changes in aerodynamic performance. In order to deeply understand the degree of wear of wind turbine blades in the wind-sand environment and its change rule with time, and to provide scientific basis for the operation and maintenance of wind turbines in the wind-sand environment, it is necessary to systematically study the dynamic evolution process of erosion and wear on the surface of the blades, as well as the change of the aerodynamic performance in this process. This study adopts the numerical model of flow-solid-erosion coupling, based on the particle concentration-time conversion method, and by simulating the erosion process of wind-sand on the wind turbine-specific airfoil S809, the dynamic evolution process of the morphology of the airfoil surface under the erosion effect of the sand particles is explored, and the depth of erosion and morphology of the airfoil surface are analyzed, and the influence law of the wind-sand particles on the morphology and its aerodynamic performance of the airfoil surface of the S809 are further investigated under different angles of attack. The influence of sand particles on the surface morphology of S809 airfoil at different angles of attack is further investigated. The study shows that, with the advancement of erosion time, the abrasion degree of sand particles on the airfoil surface increases, which makes the depth of the erosion pits deepen, and the pressure coefficient fluctuation of the airfoil surface becomes drastic. At the same time, the lift coefficient shows a trend of slight increase and then slow decrease. The particle erosion and wear were concentrated mainly in the high-pressure areas of pressure surface at the leading edge of airfoil segment. The wear area of airfoil segment was gradually enlarged with the increase of the erosion time, and the depth of wear was deepened. There was the slightly decrease rate of the maximum depth after the surface erosion of airfoil segment. The area of suction surface erosion wear was shifted to the leading edge, with the increase of angle of attack. While the area of pressure surface erosion wear was to the trailing edge. The larger the angle of attack was, the more serious the erosion wear in the region of the pressure front edge of the airfoil segment was. At the same time, the pressure coefficient of the wing section cross-section was appeared the fluctuation in the process of erosion. The more outstanding fluctuation was found with the advancement of the erosion time, especially on the more significant fluctuation of the pressure coefficient at the front edge of the suction force. Overall, the wing segment lift coefficient showed the increasing first and then decreasing in the process of particle erosion, with the advancement of erosion time. Once the angle of attack was 10° and the erosion duration was 40 h, the wing segment lift coefficient increased up to 6.3% than before. When the angle of attack was more than 12°, the coefficient of lift decreased significantly after 20 h of erosion, compared with the low angle of attack. The value of β was about 0.62 at the angle of attack from 2° to 8°, whereas, the value of β increased up to 0.82 at the angle of attack of 10°. The slow increase was observed with the increase of the angle of attack. In general, the wing segment lift-to-drag ratio was depended mainly on the incoming wind and sand at small angles of attack. There was no influence under the incoming wind and sand at large angles of attack. The findings can provide the data support and theoretical basis to maintain and repair the wind turbines in the wind-sand inflow environment.