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Time-Dependent Effects of Glaze Ice on the Aerodynamic Characteristics of an Airfoil
Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.ORCID iD: 0000-0002-6025-2280
Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.ORCID iD: 0000-0001-7599-0895
Department of Energy and Process Engineering, Faculty of Engineering, Norwegian University of Science and Technology (NTNU), Trondheim.
2018 (English)In: International Journal of Rotating Machinery, ISSN 1023-621X, E-ISSN 1542-3034, Vol. 2018, article id 2981739Article in journal (Refereed) Published
Abstract [en]

The main objective of this study is to estimate the dynamic loads acting over a glaze-iced airfoil. This work studies the performance of unsteady Reynolds-averaged Navier-Stokes (URANS) simulations in predicting the oscillations over an iced airfoil. The structure and size of time-averaged vortices are compared to measurements. Furthermore, the accuracy of a two-equation eddy viscosity turbulence model, the shear stress transport (SST) model, is investigated in the case of the dynamic load analysis over a glaze-iced airfoil. The computational fluid dynamic analysis was conducted to investigate the effect of critical ice accretions on a 0.610 m chord NACA 0011 airfoil. Leading edge glaze ice accretion was simulated with flat plates (spoiler-ice) extending along the span of the blade. Aerodynamic performance coefficients and pressure profiles were calculated and validated for the Reynolds number of 1.83 × 106. Furthermore, turbulent separation bubbles were studied. The numerical results confirm both time-dependent phenomena observed in previous similar measurements: (1) low-frequency mode, with a Strouhal number Sth≈0,013–0.02, and (2) higher frequency mode with a Strouhal number StL≈0,059–0.69. The higher frequency motion has the same characteristics as the shedding mode and the lower frequency motion has the flapping mode characteristics

Place, publisher, year, edition, pages
Hindawi Publishing Corporation, 2018. Vol. 2018, article id 2981739
National Category
Fluid Mechanics and Acoustics
Research subject
Fluid Mechanics
Identifiers
URN: urn:nbn:se:ltu:diva-67947DOI: 10.1155/2018/2981739Scopus ID: 2-s2.0-85046259848OAI: oai:DiVA.org:ltu-67947DiVA, id: diva2:1190818
Note

Validerad;2018;Nivå 1;2018-03-15 (andbra)

Available from: 2018-03-15 Created: 2018-03-15 Last updated: 2018-10-15Bibliographically approved
In thesis
1. Impact of Icing on Wind Turbines Aerodynamic
Open this publication in new window or tab >>Impact of Icing on Wind Turbines Aerodynamic
2018 (English)Doctoral thesis, comprehensive summary (Other academic)
Alternative title[sv]
Påverkan av isbildning på vindkraftverk aerodynamik
Abstract [en]

Wind energy covered 11.6% of Europe electricity demand in 2017. Region with cold climates represent a strong potential for wind energy companies because of their sparse population and proper wind conditions. The global wind energy installations in cold climate regions is forecasted to reach a capacity of 186 GW by the end of 2020. But wind turbines installed in cold climate regions are prone to the risks of ice accumulation which affects their aerodynamics behavior, as well as the safety, and structural loads.

The aerodynamic forces on wind turbine can be affected in two main ways: ice accretion changes the blade profile, and thus the flow path curvature, and the surface roughness. The importance of these two parameters depend on the ice type. The target ice type for this thesis is the smooth leading-edge glaze ice with horn shape. The aerodynamic consequences of the blade profile change because of the mentioned ice type are studied in detail. 

The findings of this thesis are classified in five main sections. The first section considers the methodology to model the performance of a wind turbine. The wake behind the turbine is also explored. Different aspects of the simulation methods with computational fluid dynamics using the Reynolds-averaged Navier-Stokes equations are investigated in both steady state and transient. In the second section, the time-dependent effects of icing are studied, exploring the moving vortices created by the irregularity of the ice and their frequencies and amplitudes. The main frequency modes of the flow dynamics were analyzed. In the third section, three-dimensional simulation of icing is implemented and the fluid flow arrangement through the rotor is investigated. Two well-recognized approaches are applied and compared, which are Blade Element Momentum (BEM) and CFD. An automated setup is programmed and launched to implement multiple CFD simulations to provide the aerodynamic data for structural analysis in the fourth section. The developed methodology is illustrated on a large-scale wind turbine. In section five, the effects of the uncertain level of ice-accretion is studied through an uncertainty quantification method. The aerodynamic losses are statistically discussed. Then, a scenario study is conducted according to the obtained polynomial chaos expansion, in which the probability distribution of wind power loss due to icing is inspected.

The achievements of this thesis can be used in to design of a wind turbine which is supposed to work in a cold climate, as well as assess the economics of a predesigned wind turbine working in a cold region.

Place, publisher, year, edition, pages
Luleå: Luleå tekniska universitet, 2018
Series
Doctoral thesis / Luleå University of Technology 1 jan 1997 → …, ISSN 1402-1544
National Category
Energy Engineering Applied Mechanics Fluid Mechanics and Acoustics
Research subject
Fluid Mechanics
Identifiers
urn:nbn:se:ltu:diva-71186 (URN)978-91-7790-228-7 (ISBN)978-91-7790-229-4 (ISBN)
Public defence
2018-12-06, E231, Luleå, Luleå, 13:00 (English)
Opponent
Supervisors
Available from: 2018-10-15 Created: 2018-10-12 Last updated: 2018-12-04Bibliographically approved

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