Boundary-layer stability and transition prediction

Background

In wind turbine design, accurate determination of aerodynamic loads is of importance as these are related to properties such as performance and structural loads. Since the aerodynamic loads can be influenced by character of the boundary layer (BL), an accurate determination of the transition location can be of significant importance to arrive at a successful wind turbine design. This has long been recognized by aerodynamicists and significant efforts have been devoted to the development of transition models.

Aims
The present study was conducted with the aim of investigating the influence and importance of three-dimensional and rotational effects on transition characteristics as well as to develop a transition analysis method that accounts for these effects. 

Approaches
An existing code for stability analysis of quasi-three-dimensional flows based on Parabolized Stability Equations (PSE) has been further developed to account for rotational effects. To provide the base flow, a quasi-three-dimensional boundary-layer model has been developed. Since information about the velocity at the boundary-layer edge is needed as input to this model, an approximate method for obtaining streamwise and spanwise edge velocities based on a two-dimensional chordwise velocity distribution has been derived. 

Keywords
Boundary-layer flow, hydrodynamic stability, transition prediction

Project leaders
Ardeshir Hanifi & Dan S. Henningson, KTH Royal Institute of Technology, Linné FLOW Centre, Dept. of Mechanics

Other project members

Mikaela Lokatt, KTH Royal Institute of Technology, Linné FLOW Centre, Dept. of Mechanics 

Niels Soerensen & Frederik Zahle, Technical University of Denmark, Department of Wind Energy