Reduced frequency effects on combined oscillations, angle of attack and free stream oscillations, for a wind turbine blade element

Kobra Gharali, Eshagh Gharaei, M. Soltani and Kaamran Raahemifar

Renewable Energy, 2018, vol. 115, issue C, 252-259

Abstract: The dynamic stall phenomenon in horizontal axis wind turbines causes significant energy waste and sometimes wind turbine failure. For modeling a deep dynamic stall phenomenon of a horizontal axis wind turbine blade element, a numerical simulation of an oscillating NREL's S809 airfoil has been performed at Reynolds number of 106 in an unsteady incident velocity; the velocity oscillates with the same frequency as the airfoil oscillation but with different phase difference (ϕ). Since the sliding mesh technique has been applied for the airfoil oscillation, an O-type grid is created resulting in the reduced number of mesh layers. A specific correction improves the quality of the O-type mesh near the sharp trailing edge. For the combined oscillations, the effects of the reduced frequency (k) in the range of 0.05≤k≤0.15 are investigated with the phase differences of ϕ=−π2, +π2,π. The results show their significant dependency on k at specific ϕ values in particular at ϕ=−π2. Combined effects of k and ϕ can change the aerodynamic loads during dynamic stall significantly compared to loads from a case with a steady incident velocity. These significant changes in the flow structure and aerodynamic loads can affect the wind turbine performance during the dynamic stall phenomenon.

Keywords: Reduced frequency; Phase difference; Dynamic stall; Pitch oscillation; Unsteady free stream (search for similar items in EconPapers)
Date: 2018
References: View references in EconPapers View complete reference list from CitEc
Citations: View citations in EconPapers (8)

Downloads: (external link)
http://www.sciencedirect.com/science/article/pii/S0960148117308005
Full text for ScienceDirect subscribers only

Related works:
This item may be available elsewhere in EconPapers: Search for items with the same title.

Export reference: BibTeX RIS (EndNote, ProCite, RefMan) HTML/Text

Persistent link: https://EconPapers.repec.org/RePEc:eee:renene:v:115:y:2018:i:c:p:252-259

DOI: 10.1016/j.renene.2017.08.042

Access Statistics for this article

Renewable Energy is currently edited by Soteris A. Kalogirou and Paul Christodoulides

More articles in Renewable Energy from Elsevier
Bibliographic data for series maintained by Catherine Liu ().