Wall Resolved Fluid-Structure Interaction Numerical Simulation of a Modern Wind Turbine Blade

Wall-resolved fluid-structure interaction (FSI) numerical simulations of the NREL 5 MW wind turbine blade are compared using two FSI approaches. The first method is based on high-fidelity Nektar++/SHARPy FSI framework, where the fluid governing equations are solved using high-order spectral/hp element method and the turbulent flow is resolved using Large Eddy Simulation (LES) on thick strips, while large-deformation dynamics of the structure are mod- elled using a geometrically exact nonlinear composite beam finite-element model. Thick strip method for the fluid reduces the computational cost by considering a series of smaller domains, each of which has a finite thickness in the spanwise direction. Hence, the overall flow over the blade is treated with a sectional approach, where in each of these sections, strips, the 3D flow is reconstructed locally. Tip-loss correction is used to compensate for the sectional approach over the blade. The second FSI approach is based on OpenFoam/Calculix coupling, where the second-order unstructured finite volume method approach is used for solving the three-dimensional flow equations and the flow turbulence is captured us- ing the k-ω SST model. The structural dynamics are modeled via second-order finite element method using standard solid elements. Effects of the solution fidelity on the prediction of aerodynamic forces as well as on the full three-dimensional flow modelling over the blade versus sectional representation of flow over the blade while incorporating the local three- dimensionality in each section and tip-correction are discussed. Further, significance of two approaches on modelling the slender blade, one using the beam mode and the other utilizing the full 3D solution of structure is addressed. Finally, assessment of computational cost and scalability of the two approaches are presented and discussed.