Multirate time stepping for aeroelastic simulations of wind turbines using the actuator line model

In this study we introduce a novel high-order tight coupling methodology based on multirate generalized additive Runge–Kutta schemes, for the aeroelastic simulations of wind turbines. A large eddy simulation framework is coupled to a multibody structural model by utilizing the multirate technique. Turbines are represented by the actuator line model. We explore two different scenarios depending on component partitioning and test them in terms of accuracy and performance. The two coupling approaches are tested in simulations of an NREL 5 MW reference wind turbine inside a uniform inflow. The scheme preserves a high-order accuracy for both coupling methods, while we observe a strong dependency of the numerical solution on the partitioning and the multirate ratio. The implemented multirate schemes demonstrate great potential for achieving algorithmic speed-ups for aeroelastic simulations compared to single-rate methods.