Abstract
Vortex generators (VGs) are used increasingly more by the wind turbine manufacture industry as flow control devices to improve rotor blade aerodynamic performance. The VG height is usually designed with equal thickness of the local boundary layer at the VG position. Nevertheless, these conventional VGs may produce excess residual drag in some applications. The so-called sub boundary layer VGs can provide enough momentum transfer over a region several times their own height for effective flow-separation control with much lower drag. The main objective is to investigate how well the simulations can reproduce the physics of the flow of the primary vortex generated by a triangular VG mounted on a flat plate with negligible pressure gradient with the angle of attack of the vane to the oncoming flow β= 18. Three different device heights H= 5mm, H1= 6,25mm, H2= 4,16mm have been studied and compared both qualitatively and quantitatively. To that end, computational simulations have been carried out using RANS method and at Reynolds number Re = 2600 based on the boundary layer momentum thickness θ= 2.4 mm at the VG position. The computational results show good agreement with the experimental data available in AVATAR project.
Highlights
Current wind turbine design is revolving around the 6 to 7 MW capacity range, with increasingly large rotor diameters
The main objective is to investigate how well the simulations can reproduce the physics of the flow of the primary vortex generated by a triangular Vortex generators (VGs) mounted on a flat plate with negligible pressure gradient with the angle of attack of the vane to the oncoming flow β= 18
In general all Computational Fluid Dynamics (CFD) and experimental curves correlations are acceptable; it is clear that the quality of correlation improves as the distance from the VG in the wake increases
Summary
Current wind turbine design is revolving around the 6 to 7 MW capacity range, with increasingly large rotor diameters. These large blades, usually pitch regulated, often have a poor aerodynamic performance near the root due to form and operation limitations, such as the required structural twist of the rotor blades or the relatively thick root sections that are needed in order to transmit the very large bending moments generated at the outer parts of the blade. The most relevant aerodynamic problem that arises is boundary layer separation on blades suction side, which causes the rotor to become unstable due to entering stall and brings an important energy loss in this region. Research on boundary layer separation control has gained in
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