Abstract
AbstractPassive vane–type vortex generators (VGs) are commonly used on wind turbine blades to mitigate the effects of flow separation. However, significant uncertainty surrounds VG design guidelines. Understanding the influence of VG parameters on airfoil performance requires a systematic approach targeting wind energy‐specific airfoils. Thus, the 30%‐thick DU97‐W‐300 airfoil was equipped with numerous VG designs, and its performance was evaluated in the Delft University Low Turbulence Wind Tunnel at a chord‐based Reynolds number of 2×106. Oil‐flow visualizations confirmed the suppression of separation as a result of the vortex‐induced mixing. Further investigation of the oil streaks demonstrated a method to determine the vortex strength. The airfoil performance sensitivity to 41 different VG designs was explored by analysing model and wake pressures. The chordwise positioning, array configuration, and vane height were of prime importance. The sensitivity to vane length, inclination angle, vane shape, and array packing density proved secondary. The VGs were also able to delay stall with simulated airfoil surface roughness. The use of the VG mounting strip was detrimental to the airfoil's performance, highlighting the aerodynamic cost of the commonly used mounting technique. Time‐averaged pressure distributions and the lift standard deviation revealed that the presence of VGs increases load fluctuations in the stalling regime, compared with the uncontrolled case.
Highlights
1.1 BackgroundThe presence of separated flow on pitch-regulated wind turbine blades is undesirable and degrades performance
The 30%-thick DU97-W-300 airfoil was equipped with numerous vortex generators (VGs) designs, and its performance was evaluated in the Delft University Low Turbulence Wind Tunnel at a chord-based Reynolds number of 2 × 106
The effect of the VGs is qualitatively assessed through the response of an oil film on the airfoil surface
Summary
The presence of separated flow on pitch-regulated wind turbine blades is undesirable and degrades performance This may manifest itself as lower annual energy production, higher fatigue loads, and stall noise.[1,2] Inboard blade flows are prone to separation since structural constraints result in thicker root airfoil sections and high local angles of attack, posing stronger adverse pressure gradients (APGs). Similar to a delta wing system (see, eg, Hoerner4), a leading edge vortex develops along the vane and is shed near the tip, creating a wake of upwash and downwash regions. This re-energizes the boundary layer with the outer flow and delays flow reversal (separation).[5]
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