Effects of Leading Edge Defect on the Aerodynamic and Flow Characteristics of an S809 Airfoil

Abstract

BackgroundUnexpected performance degradation occurs in wind turbine blades due to leading edge defect when suffering from continuous impacts with rain drops, hails, insects, or solid particles during its operation life. To assess this issue, this paper numerically investigates the steady and dynamic stall characteristics of an S809 airfoil with various leading edge defects. More leading edge defect sizes and much closer to practical parameters are investigated in the paper.MethodologyNumerical computation is conducted using the SST k-ω turbulence model, and the method has been validated by comparison with existed published data. In order to ensure the calculation convergence, the residuals for the continuity equation are set to be less than 10−7 and 10−6 in steady state and dynamic stall cases. The simulations are conducted with the software ANSYS Fluent 13.0.ResultsIt is found that the characteristics of aerodynamic coefficients and flow fields are sensitive to leading edge defect both in steady and dynamic conditions. For airfoils with the defect thickness of 6%tc, leading edge defect has a relative small influence on the aerodynamics of S809 airfoil. For other investigated defect thicknesses, leading edge defect has much greater influence on the flow field structures, pressure coefficients and aerodynamic characteristics of airfoil at relative small defect lengths. For example, the lift coefficients decrease and drag coefficients increase sharply after the appearance of leading edge defect. However, the aerodynamic characteristics could reach a constant value when the defect length is large enough. The flow field, pressure coefficient distribution and aerodynamic coefficients do not change a lot when the defect lengths reach to 0.5%c,1%c, 2%c and 3%c with defect thicknesses of 6%tc, 12%tc,18%tc and 25%tc, respectively. In addition, the results also show that the critical defect length/thickness ratio is 0.5, beyond which the aerodynamic characteristics nearly remain unchanged. In dynamic stall, leading edge defect imposes a greater influence on the aerodynamic characteristics of airfoil than steady conditions. By increasing in defect length, it is found that the separated area becomes more intense and moves forward along the suction surface.ConclusionsLeading edge defect has significant influence on the aerodynamic and flow characteristics of the airfoil, which will reach a stable status with enough large defect size. The leading edge separation bubble, circulation in the defect cavity and intense tailing edge vortex are the main features of flow around defective airfoils.

New Rotor Blade Profiles Performance Decay in Horizontal Axis Wind Turbines Operating in Aggressive Environment

“…The results have been compared with literature data as in [11], [5], [7] and [13], showing a good agreement. The comparison have suggested further experimental analysis that will be carried out as soon as possible.…”

“…4, 5 and 6. The wing sections characteristics data have been collected from [1], [5], [6], [7], [11], [12] and [13]. A preliminary analysis was carried out in [4], [4b] and [4c], while in the present paper the aerodynamic performances of new and old airfoils have been analysed and compared on a water table test bench and wind tunnel one, at "La Sapienza" University of Rome in DIMA's laboratory, with different operative running conditions resulting in different ice accretion shapes at the L.E.…”

CFD simulation on wind turbine blades with leading edge erosion

“…ANSYS Fluent 15.0 (Ansys, Inc.) is adopted in this study as it includes the well-known RANS equation and various turbulent models. The SST k-ω turbulence model is adopted throughout the study for its excellent results in the catching of flow separation and flow field details in 2D and 3D wind turbine blade simulation (Wang et al, 2016;Mo and Lee, 2012). This turbulence model effectively combines the advantages of the k-ω model in the far field with the robust and accurate of k-ω model in the near-wall region (Menter, 1994).…”

“…For the importance of understanding of the effects of leading edge erosion, researches on this topic have attracted an intense interest of scholars for the past few years (Herring et al, 2019;Ibrahim and Medraj, 2020). However, most studies were carried out with two-dimensional airfoils, such as Gharali and Johnson (2012), Wang (2017), Wang et al (2016Wang et al ( , 2017, Ge et al (2019) conducted their research on the effects of leading edge erosion with S809 airfoil, which was greatly different from the three dimensional wind turbine model. A small amount of the research calculated the power loss of the wind turbine with the leading edge erosion, but the research was carried out with the BEM theory and the software of FAST or BLADED, such as the research of Han et al (2018) and Sareen et al (2012Sareen et al ( , 2014, which just obtained the values of power output but could not present a clear elaboration on the flow structures around the turbine blade.…”

Influence of blade maximum thickness on airfoil performance with varied leading edge erosion rate

“…When the angle of attack is 10.3 °, the liftdrag ratio of erosion airfoil of sand holes and small pits is reduced by nearly 10% compared with the value of smooth airfoil, and the liftdrag ratio of trench erosion airfoil decreases by nearly 60% compared with the value of smooth airfoil (Papi et al, 2020). built a 2-dimensional FFAW3-241 airfoil erosion model to investigate different modeling stratification methods (stratification depth and leaf head cover area), reducing the lift-drag ratio by 57.74% at Re = 1.85*10 6 with a stratification depth of 5 (Wang et al, 2016). mainly studied the rectangular erosion at the leading edge of S809 airfoil.…”