Development of an aerodynamic analysis methodology for segmented ultralight morphing rotors

The Segmented Ultralight Morphing Rotor (SUMR) concept for a 50 MW wind turbine will help alleviate the technical challenges presented by a conventional upwind rotor design for such extreme-scale wind turbines. Such segmented rotor blades can bemorphed to achieve load alignment which will significantly reduce the cantilever moments, thus allowing for a lighter blade design. Depending on the wind speed, these rotors may be morphed into highly coned configurations. Consequently, a computational tool was developed in this study for the analysis of the SUMR rotors in different morphing configurations. The analysis tool was developed by modifying the Blade Element Momentum method for the morphing rotor geometry. The model was implemented in a MATLAB code, BladeMorph, and will be subsequently combined with PROPID for the purpose of rapid design and analysis of the large-scale SUMR rotors. An example 13 MW SUMR rotor, referred to as the E-13 rotor in this paper, was designed in PROPID and analyzed in BladeMorph for various cone angles to obtain C _P and C _T vs tip speed ratio curves and radial distributions of pertinent aerodynamic parameters. The predictions from BladeMorph were then compared with AeroDyn v14, and it was found that the predictions from both codes were in fairly good agreement. A large reduction in both rotor power and rotor thrust coefficients with an increase in coning angles was found. The angles of attack α, lift coefficient C _l , and drag cofficient C _d along the blade length were reduced at higher coning, while the variation in the net relative velocity, Reynolds number, and dynamic pressure along the blade was found to be minimal. Finally, with increasing coning, the axial induction distribution was found to increase toward the outboard region of the blade compared with the zero coning case, while decreasing near the inboard region of the blade.