Abstract
Gurney flaps (GFs) and microtabs (MTs) are two of the most frequently used passive flow control devices on wind turbines. They are small tabs situated close to the airfoil trailing edge and normal to the surface. A study to find the most favorable dimension and position to improve the aerodynamic performance of an airfoil is presented herein. Firstly, a parametric study of a GF on a S810 airfoil and an MT on a DU91(2)250 airfoil was carried out. To that end, 2D computational fluid dynamic simulations were performed at Re = 106 based on the airfoil chord length and using RANS equations. The GF and MT design parameters resulting from the computational fluid dynamics (CFD) simulations allowed the sizing of these passive flow control devices based on the airfoil’s aerodynamic performance. In both types of flow control devices, the results showed an increase in the lift-to-drag ratio for all angles of attack studied in the current work. Secondly, from the data obtained by means of CFD simulations, a regular function using the proper orthogonal decomposition (POD) was used to build a reduced order method. In both flow control cases (GFs and MTs), the recursive POD method was able to accurately and very quickly reproduce the computational results with very low computational cost.
Highlights
The significant increase of wind turbine size and weight in the past decade has made it impossible to control them as they were 30 years ago
Implemented and the other twelve cases were with different sizes (y) of the Gurney flaps (GFs), as illustrated in Figure 6 represents the evolution of the CL /CD ratio for each angle α and for every GF size
In the angle of attack (AoA) range from 0◦ to 6◦, the best aerodynamic performance was achieved in the case with a GF size of 0.50% of c
Summary
The significant increase of wind turbine size and weight in the past decade has made it impossible to control them as they were 30 years ago. Johnson et al [1] compiled some of the most important load control techniques that can be used in wind turbines to ensure a safe and optimal operation under a diversity of atmospheric environments. These include blades made of soft, flexible materials that change shape in response to wind speed or aerodynamic loads, aerodynamically-shaped rotating towers, flexible rotor systems with hinged blades, and other advanced control systems. The larger the size of a wind turbine, the higher the structural and fatigue loads, which affect the rotor and other key mechanisms of the turbine. Loads on wind turbines are normally divided into extreme structural loads and fatigue loads. Reducing these fatigue loads is a main goal, which can reduce the maintenance costs and improve the reliability of wind turbines (see Baek et al [2])
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