Code and Solution Verification of Sliding and Overset Grid Methods on Wind Turbine Flows

Abstract

Abstract Sliding Grids (SG) and Overset Grids (OG) are two CFD methods for discretizing the domain with several sub-grids, with the potential of enabling complex body motion in unsteady simulations. Their fundamental difference lies on the sub-grid placement, fitted into each other (SG) or overlapped (OG), which ends up impacting the information transfer mechanism that couples them. In the present work Verification procedures are applied to a novel wind turbine flow manufactured solution, followed by the aerodynamic analysis of the rotor of the NREL 5MW wind turbine. The studies aim at assessing the impact of these methods on the simulation errors, namely in terms of interpolation schemes and resulting mass imbalance, and to compare them directly performing the same task, to fulfill a gap perceived in the literature. The results suggest that SG tend to be more convenient to be used in meshes incorporating the rotor geometry, while potentially being similar to OG in terms of accuracy. This convenience consderation also derives from convergence issues with OG, which are thought to be linked with the rotating domain’s interface being too close to the turbine’s geometry. Moreover, higher than second order interpolation schemes are found to minimize the mass imbalance introduced by these methods and consequent pressure fluctuations.