Simulation of an airfoil with a deformable flap applicable in wind turbine structural load reduction

Ebrahimi, Majid; A. Shirazi, Farzad; Gharali, Kobra

doi:10.22059/ees.2020.45681

Simulation of an airfoil with a deformable flap applicable in wind turbine structural load reduction

Document Type : Research Paper

Authors

School of Mechanical Engineering, College of Engineering, University of Tehran, Tehran, Iran

10.22059/ees.2020.45681

Abstract

Flow over an airfoil equipped with Deformable Trailing Edge Flap (DTEF) has been numerically studied in a two-dimensional steady-state condition with various angles of attack. The airfoil is NACA 64-418, and the flap angle is defined by changing camber-line geometry at 10% chord length from the trailing edge. It has been shown that the direction of the flap deflection has significant impacts on aerodynamic behaviors, which provides an extra means to adjust wind turbine structural loads. Simulations have been conducted with aerodynamic-aeroelastic FAST code in the form of an open-loop control scheme to determine the DTEF's performance in a wind turbine. The wind turbine behavior has been plotted and compared for various flap angles. The load-variation ranges of the wind turbine have been identified, which help determine their sensitivity to flap changes. Finally, an open-loop control circuit is aimed at reducing the amplitude of oscillations of the blade root flapwise bending moment.

Keywords

References

[1] Franco, J. A., Jauregui, J. C., & Toledano-Ayala, M. (2015). Optimizing wind turbine efficiency by deformable structures in smart blades. Journal of Energy Resources Technology, 137(5), 051206.

[2] Andersen, T. L., Madsen, H. A., Barlas, T. K., Mortensen, U. A., & Andersen, P. B. (2015). Design, manufacturing and testing of Controllable Rubber Trailing Edge Flaps.

[3] Berg, D., Berg, J., White, J., Resor, B., & Rumsey, M. (2011). Design, fabrication, assembly and initial testing of a SMART rotor. In 49th AIAA Aerospace Sciences Meeting including the New Horizons Forum and Aerospace Exposition (p. 636).

[4] McWilliam, M., Barlas, A., Madsen, H. A., & Zahle, F. (2018). Aero-elasticWind Turbine Design with Active Flaps for AEP Maximization. Wind Energy Science Discussions, 3, 231-241.

[5] Fuglsang, P., & Bove, S. (2008). Wind tunnel testing of airfoils involves more than just wall corrections. In EWEC Conference.

[6] Timmer, W. (2009, January). An overview of NACA 6-digit airfoil series characteristics with reference to airfoils for large wind turbine blades. In 47th AIAA aerospace sciences meeting including the new horizons forum and aerospace exposition (p. 268).

[7] Bak, C., Gaunaa, M., Andersen, P. B., Buhl, T., Hansen, P., & Clemmensen, K. (2010). Wind tunnel test on airfoil Risø‐B1‐18 with an Active Trailing Edge Flap. Wind Energy: An International Journal for Progress and Applications in Wind Power Conversion Technology, 13(2‐3), 207-219.

[8] Madsen, H. A., Andersen, P. B., Andersen, T. L., Bak, C., Buhl, T., & Li, N. (2010). The potentials of the controllable rubber trailing edge flap (CRTEF). In 2010 European Wind Energy Conference and Exhibition. European Wind Energy Association (EWEA).

[9] Johnson SJ, Baker JP, van Dam CP, Berg D. An overview of active load control techniques for wind turbines with an emphasis on microtabs. Wind Energy 2010; 13(2-3): 239–253. doi:10.1002/we.356.

[10] Bergami, L., & Henriksen, L. C. (2012). Cyclic control optimization for a smart rotor. In Proceedings of the 8th PhD Seminar on Wind Energy in Europe.

[11] Bergami, L., & Poulsen, N. K. (2015). A smart rotor configuration with linear quadratic control of adaptive trailing edge flaps for active load alleviation. Wind Energy, 18(4), 625-641.

[12] Sun, X., Dai, Q., Menon, M., & Ponta, F. (2017). Design and simulation of active external trailing-edge flaps for wind turbine blades on load reduction. Journal of Aerospace Engineering, 30(5), 04017062.

[13] Henriksen, L. C., Bergami, L., & Andersen, P. B. (2013). A model based control methodology combining blade pitch and adaptive trailing edge flaps in a common framework. EWEA Annual Event, Vienna, Austria.

[14] Van Wingerden, J. W., Hulskamp, A., Barlas, T., Houtzager, I., Bersee, H., van Kuik, G., & Verhaegen, M. (2011). Two-degree-of-freedom active vibration control of a prototyped “smart” rotor. IEEE transactions on control systems technology, 19(2), 284-296.

[15] Castaignet, D., Barlas, T., Buhl, T., Poulsen, N. K., Wedel‐Heinen, J. J., Olesen, N. A. & Kim, T. (2014). Full‐scale test of trailing edge flaps on a Vestas V27 wind turbine: active load reduction and system identification. Wind Energy, 17(4), 549-564.

[16] Troldborg, N. (2005). Computational study of the Risø-B1-18 airfoil with a hinged flap providing variable trailing edge geometry. Wind Engineering, 29(2), 89-113.

[17] Barlas, T. K., Zahle, F., Sørensen, N. N., Gaunaa, M., & Bergami, L. (2012). Simulations of a rotor with active deformable trailing edge flaps in half-wake inflow: Comparison of EllipSys 3D with HAWC2. In EWEA 2012-European Wind Energy Conference & Exhibition. European Wind Energy Association (EWEA).

[18] Andersen, P. B., Gaunaa, M., Bak, C., & Hansen, M. H. (2009). A dynamic stall model for airfoils with deformable trailing edges. Wind Energy: An International Journal for Progress and Applications in Wind Power Conversion Technology, 12(8), 734-751.

[19] Gaunaa, M. (2006). Unsteady 2D potential-flow forces on a thin variable geometry airfoil undergoing arbitrary motion.

[20] Bergami, L., Riziotis, V. A., & Gaunaa, M. (2015). Aerodynamic response of an airfoil section undergoing pitch motion and trailing edge flap deflection: a comparison of simulation methods. Wind Energy, 18(7), 1273-1290.

[21] Jonkman, J., Butterfield, S., Musial, W., & Scott, G. (2009). Definition of a 5-MW reference wind turbine for offshore system development (No. NREL/TP-500-38060). National Renewable Energy Lab. (NREL), Golden, CO (United States).

[22] airfoil tools. 2018. airfoil tools. [ONLINE] Available at: http://airfoiltools.com/. [Accessed 1 November 2018].