Space–Time Isogeometric Analysis of NREL 5MW wind turbine rotor and tower aerodynamics

Abstract We present the Space–Time Isogeometric Analysis (ST-IGA) of wind turbine rotor and tower aerodynamics, with the rotor geometry of the NREL 5MW offshore baseline wind turbine. The computation is with a given wind speed and a specified rotor speed. The computational challenges include accurate representation of the rotor geometry, multiscale nature of the unsteady flow, the fast, rotational relative motion between the rotor and tower, and the IGA mesh generation for the complex geometry. In addressing the computational challenges, the ST-IGA is used together with the ST Variational Multiscale (ST-VMS) method, which is a core computational method, and the ST Slip Interface (ST-SI) and Complex-Geometry IGA Mesh Generation (CGIMG) methods, which are complementary general-purpose methods. These are the methods of the ST Computational Flow Analysis in this case. The ST-discretization feature provides higher-order accuracy compared to standard discretization methods. The VMS feature addresses the computational challenges associated with the multiscale nature of the unsteady flow. The moving-mesh feature of the ST framework enables high-resolution computation near the blades. The ST-SI enables high-fidelity moving-mesh computations even over meshes made of patches with nonmatching meshes at the interfaces between those patches. The mesh covering the rotor rotates with it, and the SI between the rotating mesh and the rest of the mesh accurately connects the two sides of the solution. The ST-IGA, with IGA basis functions in space, enables more accurate representation of the rotor geometry and increased accuracy in the flow solution. With IGA basis functions in time, it enables more accurate representation of the rotor and mesh rotations. The CGIMG makes it easier in IGA mesh generation to deal with the complex geometry. The computation presented shows that the ST-IGA and the accompanying methods are successful in addressing the challenges and bringing high-fidelity computational analysis to wind turbine rotor and tower aerodynamics.