Parametric Study of a Gurney Flap Implementation in a DU91W(2)250 Airfoil

The growth in size and weight of wind turbines over the last years has led to the development of flow control devices, such as Gurney flaps (GFs). In the current work, a parametric study is presented to find the optimal GF length to improve the airfoil aerodynamic performance. Therefore, the influence of GF lengths from 0.25% to 3% of the airfoil chord c on a widely used DU91W(2)250 airfoil has been investigated by means of RANS based numerical simulations at Re = 2 × 106. The numerical results showed that, for positive angles of attack, highest values of the lift-to-drag ratio CL/CD are obtained with GF lengths between 0.25% c and 0.75% c. Particularly, an increase of 21.57 in CL/CD ratio has been obtained with a GF length of 0.5% c at 2° of angle of attack AoA. The influence of GFs decreased at AoAs larger than 5°, where only a GF length of 0.25% c provides a slight improvement in terms of CL/CD ratio enhancement. Additionally, an ANN has been developed to predict the aerodynamic efficiency of the airfoil in terms of CL/CD ratio. This tool allows to obtain an accurate prediction model of the aerodynamic behavior of the airfoil with GFs.

[1]  Ajay Kumar Kaviti,et al.  Performance evaluation of profile modifications on straight-bladed vertical axis wind turbine by energy and Spalart Allmaras models , 2017 .

[2]  Christian Oliver Paschereit,et al.  Wake Analysis of a Finite Width Gurney Flap , 2015 .

[3]  George N. Barakos,et al.  Performance improvement of variable speed rotors by Gurney flaps , 2018, Aerospace Science and Technology.

[4]  Jorge León Colman Lerner,et al.  Experimental Study Of A Naca 4412 Airfoil With Movable Gurney Flap , 2011 .

[5]  Ekaitz Zulueta,et al.  Microtab Design and Implementation on a 5 MW Wind Turbine , 2017 .

[6]  Davide Astolfi,et al.  Wind Turbine Power Curve Upgrades , 2018 .

[7]  F. Menter.  Two-equation eddy-viscosity turbulence models for engineering applications , 1994 .

[8]  Ekaitz Zulueta,et al.  Dual model oriented modeling of monocrystalline PV modules based on artificial neuronal networks , 2017 .

[9]  Earl H. Dowell,et al.  Aerodynamic Loading for an Airfoil with an Oscillating Gurney Flap , 2007 .

[10]  Tim Lee,et al.  Lift enhancement and flow structure of airfoil with joint trailing-edge flap and Gurney flap , 2011 .

[11]  R. Liebeck.  Design of Subsonic Airfoils for High Lift , 1976 .

[12]  T. Lutz,et al.  CFD code comparison for 2D airfoil flows , 2016 .

[13]  Jinjun Wang,et al.  Gurney flap—Lift enhancement, mechanisms and applications , 2008 .

[14]  David W. Hurst,et al.  Aerodynamics of Gurney Flaps on a Single-Element High-Lift Wing , 2000 .

[15]  Scott J. Johnson,et al.  Active load control techniques for wind turbines. , 2008 .

[16]  Ekaitz Zulueta,et al.  Flow Control Devices for Wind Turbines , 2017 .

[17]  Unai Fernández Gamiz,et al.  Computational Modeling of Gurney Flaps and Microtabs by POD Method , 2018 .

[18]  James G. Coder,et al.  Experimental Investigation into the Effect of Gurney Flaps on Various Airfoils , 2013 .

[19]  George N. Barakos,et al.  Effect of active Gurney flaps on overall helicopter flight envelope , 2016, The Aeronautical Journal.

[20]  Ekaitz Zulueta,et al.  Five Megawatt Wind Turbine Power Output Improvements by Passive Flow Control Devices , 2017 .

[21]  Eduard Egusquiza,et al.  Testing of self-similarity and helical symmetry in vortex generator flow simulations , 2016 .

[22]  George N. Barakos,et al.  Rotor Computations with Active Gurney Flaps , 2016 .

[23]  Sergio Preidikman,et al.  Numerical simulations of the aerodynamic behavior of large horizontal-axis wind turbines , 2010 .

[24]  Bruce L. Storms,et al.  Lift enhancement of an airfoil using a Gurney flap and vortex generators , 1993 .

[25]  Mark Woodgate,et al.  CFD Method for Modelling Gurney Flaps , 2017 .

[26]  M. Vinokur,et al.  On one-dimensional stretching functions for finite-difference calculations. [computational fluid dynamics] , 1983 .

[27]  W. A. Timmer,et al.  Summary of the Delft University Wind Turbine Dedicated Airfoils , 2003 .

[28]  Ekaitz Zulueta,et al.  Systematic modeling of photovoltaic modules based on artificial neural networks , 2016 .

[29]  Davide Astolfi,et al.  Innovative methods for wind turbine power curve upgrade assessment , 2018 .

[30]  C. P. van Dam,et al.  Computational Investigation of Finite Width Microtabs for Aerodynamic Load Control , 2005 .

[31]  L. D. Kral.  Recent experience with different turbulence models applied to the calculation of flow over aircraft components , 1998 .

[32]  Oscar Barambones,et al.  Computational Modelling of Rectangular Sub-Boundary Layer Vortex Generators , 2018 .