Computational methods for fluid-structure interaction in flexible wind turbine blades

To provide an accurate and computationally efficient methodology for FSI research, this study develops a CFD/CSD coupling model based on a loosely coupled strategy, implemented via a fully in-house solver. Within the CFD component, a dual-grid/dual-solver approach based on the overset grid method is employed to leverage the respective strengths of different numerical techniques while circumventing their individual limitations. For the near-body region, an unstructured hybrid grid finite volume method solves the RANS equations, enabling accurate simulation of boundary layer flows over the blade surface at a relatively low grid cost for complex geometries. Simultaneously, in the off-body region, a fifth-order WENO scheme on an adaptive Cartesian grid is used to improve the resolution of the wake and tip vortices, where the regularity of Cartesian grids facilitates the efficient implementation of high-order schemes without the need for full-domain high-order curved mesh generation. Within the CSD component, a nonlinear structural dynamics model for the flexible blades is developed based on geometrically exact beam theory. Additionally, the finite rotation method is applied to manage CFD grid deformation. By confining the high-order scheme to the off-body region and employing adaptive mesh refinement only where needed, the proposed approach enhances wake resolution while avoiding the excessive computational cost associated with global high-order methods. The model offers advantages including accurate aerodynamic calculations, improved wake resolution, and modeling of geometric nonlinear structural characteristics.