Laminar-Turbulent transition on Wind Turbines

Publication: ResearchPh.D. thesis – Annual report year: 2011

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The present thesis deals with the study of the rotational effects on the
laminar-turbulent transition on wind turbine blades.
Linear stability theory is used to formulate the stability equations that
include the effect of rotation. The mean flow required as an input to stability
computations is obtained by a similarity transformation technique.
This approach allows to transform the boundary layer equations that have
included the effect of the Coriolis and centrifugal forces into a set of couple
partial differential equations, that are more convenient to solve numerically.
The solution have been parametrized and adapted to an wind turbine rotor
geometry. The blade is resolved in radial sections along which calculations
are performed. The obtained mean flow is classified according to the parameters
used on the rotating configuration, geometry and operational conditions.
The stability diagrams have been obtained by solving the stability
equations as an eigenvalue problem. The Keller box Scheme that is second
order accurate was used as a numerical method. Have found to be stable and
effective in terms of computing time. The solution of the eigenvalue problem
provide connection between the parameters used to define the resultant wave
magnitude and direction. The propagation of disturbances in the boundary
layers in three dimensional flows is relatively a complicated phenomena.
The report discusses the available methods and techniques used to predict
the transition location. Some common wind turbine airfoils are selected to
performe parametrical studies with rotational effects. Finally a wind turbine
rotor is used for comparison with transition experiments. The relative
motion between the flow and the blade geometry defines the response of
the flow to disturbances. Have been found that flow on the suction side of
the blade has a stabilizating effect, while on the region from the stagnation
point to the rotor plane has a destabilizating effect on the boundary layer.
The tendency is that rotational effect stabilize the boundary layer on the
wind turbine blade.
Original languageEnglish
Publication date2012
Place of publicationKgs. Lyngby
PublisherDTU Mechanical Engineering
Number of pages133
StatePublished
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