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Simulating Dynamic Stall Effects for Vertical Axis Wind Turbines Applying a Double Multiple Streamtube Model
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
2015 (English)In: Energies, ISSN 1996-1073, Vol. 8, no 2, 1353-1372 p.Article in journal (Refereed) Published
Abstract [en]

The complex unsteady aerodynamics of vertical axis wind turbines (VAWT) poses significant challenges to the simulation tools. Dynamic stall is one of the phenomena associated with the unsteady conditions for VAWTs, and it is in the focus of the study. Two dynamic stall models are compared: the widely-used Gormont model and a Leishman-Beddoes-type model. The models are included in a double multiple streamtube model. The effects of flow curvature and flow expansion are also considered. The model results are assessed against the measured data on a Darrieus turbine with curved blades. To study the dynamic stall effects, the comparison of force coefficients between the simulations and experiments is done at low tip speed ratios. Simulations show that the Leishman-Beddoes model outperforms the Gormont model for all tested conditions.

Place, publisher, year, edition, pages
2015. Vol. 8, no 2, 1353-1372 p.
National Category
Electrical Engineering, Electronic Engineering, Information Engineering
URN: urn:nbn:se:uu:diva-253091DOI: 10.3390/en8021353ISI: 000353561900001OAI: diva2:814437
StandUpSwedish Energy Agency
Available from: 2015-05-27 Created: 2015-05-20 Last updated: 2015-10-01Bibliographically approved
In thesis
1. Aerodynamics of Vertical Axis Wind Turbines: Development of Simulation Tools and Experiments
Open this publication in new window or tab >>Aerodynamics of Vertical Axis Wind Turbines: Development of Simulation Tools and Experiments
2015 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

This thesis combines measurements with the development of simulation tools for vertical axis wind turbines (VAWT). Numerical models of aerodynamic blade forces are developed and validated against experiments. The studies were made on VAWTs which were operated at open sites. Significant progress within the modeling of aerodynamics of VAWTs has been achieved by the development of new simulation tools and by conducting experimental studies.        

An existing dynamic stall model was investigated and further modified for the conditions of the VAWT operation. This model was coupled with a streamtube model and assessed against blade force measurements from a VAWT with curved blades, operated by Sandia National Laboratories. The comparison has shown that the accuracy of the streamtube model has been improved compared to its previous versions. The dynamic stall model was further modified by coupling it with a free vortex model. The new model has become less dependent on empirical constants and has shown an improved accuracy.    

Unique blade force measurements on a 12 kW VAWT were conducted. The turbine was operated north of Uppsala. Load cells were used to measure the forces on the turbine. A comprehensive analysis of the measurement accuracy has been performed and the major error sources have been identified.

The measured aerodynamic normal force has been presented and analyzed for a wide range of operational conditions including dynamic stall, nominal operation and the region of high flow expansion. The improved vortex model has been validated against the data from the new measurements. The model agrees quite well with the experiments for the regions of nominal operation and high flow expansion. Although it does not reproduce all measurements in great detail, it is suggested that the presented vortex model can be used for preliminary estimations of blade forces due to its high computational speed and reasonable accuracy.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2015. 86 p.
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 1274
wind power, vertical axis turbine, H-rotor, simulations, streamtube model, vortex model, dynamic stall, measurements, blade, force
National Category
Engineering and Technology
Research subject
Engineering Science with specialization in Science of Electricity
urn:nbn:se:uu:diva-260573 (URN)978-91-554-9307-3 (ISBN)
Public defence
2015-10-09, Polhemssalen, Ångströmlaboratoriet, Lägerhyddsvägen 1, Uppsala, 09:00 (English)
Available from: 2015-09-17 Created: 2015-08-20 Last updated: 2015-10-01

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