Document Type : Original Article


1 Faculty of Mechanical Engineering, Shahrood University of Technology, Shahrood, Iran.

2 Aerospace Engineering Department, Sharif University of Technology, Tehran, Iran


Multi-Megawatt wind turbines have long, slender and heavy blades that can undergo extremely wind loadings. Good understanding of the modal dynamics of these large machines is of great priority. In this paper, modal dynamics of NREL 5 MW wind turbine is investigated. To this aim, FAST software has been implemented. Vibration characteristics of blades, tower and whole wind turbine machine is extracted. To examine the effects of wind velocity, two operating conditions of machine have been considered. Namely: normal operating condition at rated wind velocity and rated rotor speed and the other, parked condition with fixed rotor at the wind velocity equal to rated wind velocity. Blades root bending moments (both in plane and out of plane) and tower bending moments (both longitudinal and lateral) are extracted. Frequency spectrum of the results is utilized as a tool to study the effects of each vibration mode on wind turbine dynamics in each of aforementioned operating conditions. It is shown that tower vibration during normal operation is highly influenced from blade edge-wise bending mode. On the other hand, during parked condition the effects of flap-wise bending modes become more dominant. The results are expected to offer better predictions of the vibrational behavior of large wind turbines.


[1] Alayi, R., Jahangiri, M., Guerrero, J. W. G., Akhmadeev, R., Shichiyakh, R. A., and Zanghaneh, S. A. (2021). Modelling and reviewing the reliability and multi-objective optimization of wind-turbine system and photovoltaic panel with intelligent algorithms. Clean Energy, 5(4), 713-730.‏
[2] Alayi, R. and Velayti, J. (2021). Modeling/optimization and effect of environmental variables on energy production based on PV/Wind turbine hybrid system. Jurnal Ilmiah Teknik Elektro Komputer dan Informatika (JITEKI), 7(1), 101-107.‏
[3] Alayi, R., Zishan, F., Seyednouri, S. R., Kumar, R., Ahmadi, M. H., and Sharifpur, M. (2021). Optimal load frequency control of island micro-grids via a PID controller in the presence of wind turbine and PV. Sustainability, 13(19), 10728.‏
[4] Ganjei, N., Zishan, F., Alayi, R., Samadi, H., Jahangiri, M., Kumar, R., and Mohammadian, A. (2022). Designing and Sensitivity Analysis of an Off-Grid Hybrid Wind-Solar Power Plant with Diesel Generator and Battery Back-up for the Rural Area in Iran. Journal of Engineering, 2022.
[5] The world wind energy association website (2022), Available:
[6] The national renewable energy website (2022), Available:
[7] Heinz, J. C. et al. (2016). Vortex-induced vibrations on a modern wind turbine blade, Wind Energy, Vol. 19, pp. 2041–2051.
[8] Bak, C., et al. (2013). The DTU 10-MW reference wind turbine in Danish Wind Power Research (Danish Technical University).
[9] Skrzypiński, W. et al. (2014). Vortex-induced vibrations of a DU96-W-180 airfoil at 90 angle of attack, Wind Energy, Vol. 17, pp. 1495–1514.
[10] Lekou, D. et al. (2015). AVATAR deliverable D1.2: Reference blade design, Technical Report No. D1.2 (ECN Wind Energy, Petten, The Netherlands).
[11] Horcas, S. G. et al. (2020). Vortex induced vibrations of wind turbine blades: Influence of the tip geometry, Physics of Fluids, Vvol. 32, 065104.
[12] Bortolotti, P., et. al. (2019). Systems engineering in wind energy—WP2.1 reference wind turbines, Report No. NREL/TP-5000-73492.
[13] Hoang, M. C. et al. (2015). Experimental study on aerodynamic coefficients of yawed cylinders, Journal of Fluids and Structures, Vol. 54, pp. 597–611.
[14] Bourguet, R. and Triantafyllou, M. S. (2015). Vortex-induced vibrations of a flexible cylinder at large inclination angle, Philosophical Transactions of the Royal Society A, Vol. 373, 20140108.
[15] Horcas, S. G. et al. (2019). Suppressing vortex induced vibrations of wind turbine blades with flaps, In: Ferrer, E. and Montlaur, A. (Eds.), Springer Tracts in Mechanical Engineering, pp. 11–24.
[16] Jonkman, B. and Jonkman, J. (2016). Fast V8. 16.00 a-bjj. NREL.
[17] Jonkman, J. et al. (2009). Definition of a 5-MW reference wind turbine for offshore system development, NREL.
[18] Farsadi, T. and Kayran, A. (2021). Flutter study of flapwise bend-twist coupled composite wind turbine blades, Wind and Structures, Vol. 32 (3), pp. 267-281.
[19] Hansen, M. (2007). Aeroelastic instability problems for wind turbines, Wind Energy, Vol. 10(6), pp. 551–577.
[20] Becker, M. (2017). Fastfoam-an aero-servo-elastic wind turbine simulation method based on CFD.
[21] Mettam, G.R. and Adams, L. B. (1999). How to prepare an electronic version of your article, In: Jones, B.S. and Smith, R.Z. (Eds.), Introduction to the Electronic Age. E-Publishing Inc., New York, pp. 281-304.