Wind turbine power optimisation is usually done with a blade element momentum (BEM) model using tabulated 2D airfoil polars of lift and drag. Current BEM models correct the airfoil polars for 3D crossflow by utilising a method that accounts for the pressure forces but neglects the viscous friction forces. Since swept blade turbines experience more crossflow, the power loss due to friction is probably underestimated for such turbines.

In a new paper, Gaunaa, Sørensen, and Li (2024) suggest an improvement to the crossflow correction model: It considers friction forces using a classic flat-plate solution. The authors verify the new crossflow model against 3D computational fluid dynamics and examine the power production of a 10MW swept-wing turbine with and without friction forces. Results show that including viscous forces in the crossflow model significantly changes the modelled power production for wind turbines with large sweep angles.

Gaunaa, Mac, Niels N. Sørensen, and Ang Li. 2024. “A Correction Model for the Effect of Spanwise Flow on the Viscous Force Contribution in BEM and Lifting Line Methods.” Journal of Physics: Conference Series 2767 (2): 022068. https://iopscience.iop.org/article/10.1088/1742-6596/2767/2/022068