Implementing a Dynamic Stall Model for Airfoils with Deformable Trailing Edges

Unsteady two‐dimensional potential‐flow model for thin variable geometry airfoils

“…25 Comparison between results obtained with twodimensional Navier-Stokes simulations and the present theory 21,37 shows that despite the crude simplifying assumptions, the model captures the main physics well for attached fl ow. The current theory is used in a more practical application in a number of studies [13][14][15][16][17][18]38 for assessment of the load reduction potential using airfoils with variable trailing-edge geometry on wind turbines. To this end, a dynamic stall model for variable trailing-edge geometry airfoils has been formulated by Andersen et.…”

“…The initial studies 13,14 were confi ned to investigations for which attached fl ow is a good approximation, and the present model was used directly. The latter investigations [15][16][17][18] use the dynamic stall model for variable trailing-edge geometry airfoils formulated by Andersen et al 19 That model can be considered an extension of the main elements of the present model extended with the effects of viscosity in the spirit of the Beddoes-Leishman type dynamic stall model described by Hansen et al 20 Since modern wind turbines have gravitated towards using pitch-regulated variable-speed (PRVS) control only, where the fl ow on the outer part of the blades is attached, an unsteady potential fl ow model describes the main part of the unsteady aerodynamic behaviour of these sections well. It is also for the outer sections where variable trailing-edge geometry is most effective for fatigue load reduction (see Andersen and Andersen et al).…”

“…Up to the development of the present theory, aerodynamic calculation of such problems has only been possible with computationally rather expensive methods, rendering aeroelastic and aeroservoelastic computations very time consuming in these cases. Recent two-and three-dimensional investigations based on the present aerodynamic model [13][14][15][16][17][18] have shown that there is a big potential of fatigue load reduction on wind turbines using airfoils with variable trailing-edge geometry. The initial studies 13,14 were confi ned to investigations for which attached fl ow is a good approximation, and the present model was used directly.…”

“…It is also for the outer sections where variable trailing-edge geometry is most effective for fatigue load reduction (see Andersen and Andersen et al). 13,18 For the studies of full turbines, 13,[15][16][17][18] the three-dimensional aerodynamic response is predicted using the blade element momentum method with the commonly used extensions for unsteady effects. The innermost part of these extensions includes two-dimensional models for the unsteady aerodynamics.…”

Deformable trailing edge flaps for modern megawatt wind turbine controllers using strain gauge sensors

“…At Risø DTU, a computationally very effi cient unsteady two-dimensional potential-fl ow model for the aerodynamic forces of a thin airfoil undergoing deformation of the camberline was developed. 7 Andersen et al 3,24 extended the model to include viscous effects in the spirit of the Risø version 25 of the Beddoes-Leishman-type dynamic stall model. 26 The traditional blade element momentum (BEM) models cannot include trailing edge deformations in a direct way; consequently, the near-wake model for trailing vorticity originally proposed by Beddoes 27 and investigated by Madsen and Rasmussen 28 has been implemented in HAWC2 following the work of Andersen et al 29 Subsequently, the aerodynamic part of HAWC2 comprises a near-wake model, 29 a dynamic stall model, 3,24 the farwake part of a dynamic infl ow model, 30 a potential tower shadow model and the tip loss correction by Wilson and Lissaman.…”