PhD ceremony Ms. H.A. Bijleveld: A quasi-simultaneous interaction method for the determination of the aerodynamic forces on wind turbine blades

PhD ceremony: Ms. H.A. Bijleveld, 14.30 uur, Academiegebouw, Broerstraat 5, Groningen

Dissertation: A quasi-simultaneous interaction method for the determination of the aerodynamic forces on wind turbine blades

Promotor(s): prof. A.E.P. Veldman

Faculty: Mathematics and Natural Sciences

For accurate prediction of aerodynamic forces on wind turbine blades a method is required that is more accurate than the current Blade Element Momentum methods, but has a slight increase in computational cost. Therefore, the flow field is decomposed into an inviscid and viscous region. The inviscid region is modeled as a potential flow and the viscous region as a boundary layer flow. To account for the interaction (in reality this division in regions does not exist) an interaction method is applied. We apply the quasi-simultaneous interaction method. This method is a combination of the advantages of the direct and simultaneous method.

In the quasi-simultaneous interaction method the boundary layer flow is solved simultaneously with an approximation of the potential flow. The approximation consists of only the local effects of the potential flow and is modeled as a relation between the velocity and displacement thickness. This relation is called the interaction law. It is formulated such that the converged result is not influenced by its precise formulation and is chosen to be as simple as possible: a linear relation where the coefficient depends only on the local grid size.

The value of the coefficient ensures that in 2D flows the eigenvalues of the system of equations are always positive (the Goldstein singularity is avoided) and that in 3D flows they scale with the cross flow.

The resulting method is robust and converges for both attached and separated flows. Results of 2D simulations agree extremely well with experiments.