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Near-Wake Flow Simulation of a Vertical Axis Turbine Using an Actuator Line Model
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.ORCID iD: 0000-0001-5006-9231
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.ORCID iD: 0000-0002-6975-1588
2018 (English)In: Wind Energy, ISSN 1095-4244, E-ISSN 1099-1824Article in journal (Refereed) Published
Abstract [en]

In the present work, the near‐wake generated for a vertical axis wind turbine (VAWT) was simulated using an actuator line model (ALM) in order to validate and evaluate its accuracy. The sensitivity of the model to the variation of the spatial and temporal discretization was studied and showed a bigger response to the variation in the mesh size as compared with the temporal discretization. The large eddy simulation (LES) approach was used to predict the turbulence effects. The performance of Smagorinsky, dynamic k‐equation, and dynamic Lagrangian turbulence models was tested, showing very little relevant differences between them. Generally, predicted results agree well with experimental data for velocity and vorticity fields in representative sections. The presented ALM was able to characterize the main phenomena involved in the flow pattern using a relatively low computational cost without stability concerns, identified the general wake structure (qualitatively and quantitatively), and the contribution from the blade tips and motion on it. Additionally, the effects of the tower and struts were investigated with respect to the overall structure of the wake, showing no significant modification. Similarities and discrepancies between numerical and experimental results are discussed. The obtained results from the various simulations carried out here can be used as a practical reference guideline for choosing parameters in VAWTs simulations using the ALM.

Place, publisher, year, edition, pages
2018.
National Category
Engineering and Technology
Identifiers
URN: urn:nbn:se:uu:diva-348688DOI: 10.1002/we.2277OAI: oai:DiVA.org:uu-348688DiVA, id: diva2:1198214
Funder
StandUp for WindAvailable from: 2018-04-17 Created: 2018-04-17 Last updated: 2018-10-15
In thesis
1. Aerodynamic Studies of Vertical Axis Wind Turbines using the Actuator Line Model
Open this publication in new window or tab >>Aerodynamic Studies of Vertical Axis Wind Turbines using the Actuator Line Model
2018 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

This thesis addresses the unsteady aerodynamics involved in the operation of vertical axis wind turbines (VAWTs). The main focus is to represent and understand the most relevant phenomena within the resulting flow pattern as the wake structure, loads on the different turbine components and the performance of the rotor. An actuator line model has been used for this purpose.

This model has been validated against experimental measurements from diverse cases with different operating conditions in both confined wind tunnels and open site locations. Numerical works were carried out considering a wide range of tip speed ratios (TSRs), and therefore covering from the no stall to the deep stall regime. The latter requires the implementation of a dynamic stall model for the proper representation of the unsteady forces on the blades. Also, different inlet conditions such as a uniform flow, a logarithmic wind shear and an atmospheric boundary layer (ABL) have been tested. The so-called recycling method technique was used to produce the fully developed ABL flow. Additionally, the resulting wake and performance of interacting turbines has been studied.

Once the model was validated, two numerical study cases for large scale turbines were carried out. First, the performance and resulting flow field from both a horizontal axis wind turbine (HAWT) and VAWT were investigated when the turbines were operating at their optimal TSR and within the same ABL inflow boundary conditions. The influence of the variation on the atmospheric turbulence levels was also studied, as well as the differences and similarities on the obtained results for both type of turbines. Later, the performance improvement of two interacting VAWTs was investigated through the deflected wake produced by the pitched struts of the upstream turbine. This is presented as a novel mechanism to mitigate losses on interacting turbine arrangements (i.e. wind farms).

In general, there is a reasonable good agreement between numerical results and experimental measurements, and therefore, the applied ALM can be considered as a potential tool for VAWTs simulations, characterized by relatively low computational cost showing accuracy and numerical stability.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2018. p. 85
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 1671
Keywords
wind power, vertical axis wind turbines (VAWTs), actuator line model (ALM), dynamic stall model (DSM), atmospheric boundary layer (ABL), wake deflection, atmospheric boundary layer (ABL)
National Category
Engineering and Technology
Research subject
Engineering Science with specialization in Science of Electricity
Identifiers
urn:nbn:se:uu:diva-348346 (URN)978-91-513-0338-3 (ISBN)
Public defence
2018-06-05, Häggsalen, Ångströmlaboratoriet, Lägerhyddsvägen 1, Uppsala, 09:00 (English)
Opponent
Supervisors
Funder
StandUp for Wind
Available from: 2018-05-15 Created: 2018-04-11 Last updated: 2018-10-08

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Mendoza, VictorGoude, Anders

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