Design and optimization of wing tips for wind turbines

The objective of the project was to develop and analyse new designs of wing tips for wind turbines. During the project various numerical tools have been developed based on lifting line theory and computational fluid dynamics (CFD). Furthermore, a new formulation of the tip correction has been derived and an analyis of the flow topology of the limiting streamlines near the tip has been carried out. during the project a series of wing tips and their flow topology have been investigated, and the importance of various design variables have been determined. The detailed computations have mainly been carried out using the CFD code EllipSys. The results from the computations have provided important information regarding load distributions and low topology. As a supplement to the viscous computations, various inviscid computations have been performed using lifting line theory. Lifting line theory is many times faster than CFD and a part of the project focused on developing a fast and reliable numerical lifting lilne method. Besides providing information about the aerodynamics of wing tips, the computations formed the basis for improving the tip loss correction. The tip loss correction was originally developed as a fix in the blade-element momentum technique to correct the axisymmetric momentum theory for finte number blades. Although the expression forming the tip loss correction contains an inherent inconsistency, it has largely been used in its original form since it was derived in the 1920s. Based on the CFD computations int he present project, a refined formulation has been proposed and validated