Change search
ReferencesLink to record
Permanent link

Direct link
On the wake flow interaction between two perforated discs with varying mutual distance
KTH, School of Engineering Sciences (SCI), Mechanics, Fluid Physics. KTH, School of Engineering Sciences (SCI), Centres, Linné Flow Center, FLOW.
KTH, School of Engineering Sciences (SCI), Mechanics, Fluid Physics. KTH, School of Engineering Sciences (SCI), Centres, Linné Flow Center, FLOW.ORCID iD: 0000-0002-3251-8328
(English)Manuscript (preprint) (Other academic)
National Category
Mechanical Engineering
URN: urn:nbn:se:kth:diva-144517OAI: diva2:713839

QS 2014

Available from: 2014-04-24 Created: 2014-04-24 Last updated: 2014-04-24Bibliographically approved
In thesis
1. Wind-turbine wake flows - Effects of boundary layers and periodic disturbances
Open this publication in new window or tab >>Wind-turbine wake flows - Effects of boundary layers and periodic disturbances
2014 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The increased fatigue loads and decreased power output of a wind turbine placed in the wake of another turbine is a well-known problem when building new wind-power farms and a subject of intensive research. These problems are caused by the velocity gradients and high turbulence levels present in the wake of a turbine. In order to better estimate the total power output and life time of a wind-power farm, knowledge about the development and stability of wind-turbine wakes is crucial.

In the present thesis, the flow field around small-scale model wind turbines has been investigated experimentally in two wind tunnels. The flow velocity was measured with both hot-wire anemometry and particle image velocimetry. To monitor the turbine performance, the rotational frequency, the power output and the total drag force on the turbine were also measured. The power and thrust coefficients for different tip-speed ratios were calculated and compared to the blade element momentum method, with a reasonable agreement. The same method was also used to design and manufacture new turbine blades, which gave an estimate of the distribution of the lift and drag forces along the blades.

The influence of the inlet conditions on the turbine and the wake properties was studied by subjecting the turbine to both uniform in flow and different types of boundary layer in flows. In order to study the stability and development of the tip vortices shed from the turbine blades, a new experimental setup for phase-locked measurements was constructed. The setup made it possible to introduce perturbations of different frequencies and amplitudes, located in the rear part of the nacelle. With a newly developed method, it was possible to characterize the vortices and follow their development downstream, using only the streamwise velocity component.

Measurements were also performed on porous discs placed in different configurations. The results highlighted the importance of turbine spacings. Both the measurements on the turbine and the discs were also used to compare with large eddy simulations using the actuator disc method. The simulations managed to predict the mean velocity fairly well in both cases, while larger discrepancies were seen in the turbulence intensity.


Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2014. viii, 35 p.
TRITA-MEK, ISSN 0348-467X ; 2014:12
wind power, wind-turbine model, wind tunnel, porous disc, hot-wire anemometry, particle image velocimetry, blade element momentum method, large eddy simulations, actuator disc method
National Category
Fluid Mechanics and Acoustics
urn:nbn:se:kth:diva-144475 (URN)978-91-7595-112-6 (ISBN)
Public defence
2014-05-14, D2, Lindstedtsvägen 5, KTH, Stockholm, 10:15 (English)
Swedish Energy Agency

QC 20140424

Available from: 2014-04-24 Created: 2014-04-23 Last updated: 2014-04-24Bibliographically approved

Open Access in DiVA

No full text

Search in DiVA

By author/editor
Odemark, YlvaFransson, Jens
By organisation
Fluid PhysicsLinné Flow Center, FLOW
Mechanical Engineering

Search outside of DiVA

GoogleGoogle Scholar
The number of downloads is the sum of all downloads of full texts. It may include eg previous versions that are now no longer available

Total: 32 hits
ReferencesLink to record
Permanent link

Direct link